lekq7518 g3500 engine basics

G3500EngineBasics

LEKQ7518 8-97

G3500 Engine BasicsEngine Design

G3508G3512G3516

Electronic Ignition System (EIS)EIS Control ModuleIgnition TransformersEngine Sensors

Fuel, Air Inlet and Exhaust SystemsEngine BasicsFuel SystemAir Inlet and Exhaust Systems

Lubrication System

Cooling SystemJacket Water SystemSeparate Circuit Aftercooler (SCAC) System

Basic BlockCylinder Block, Liners and HeadsPistons, Rings and Connecting RodsCrankshaftCamshafts

Electrical SystemEngine Electrical SystemCharging System ComponentsGrounding Practices

Starting SystemsElectricAir Start

Engine Monitoring and Shutdown ProtectionJunction BoxEngine Start/Stop PanelDC Control Panel for Gas Engine ChillerDC Control Panel for Gas Engine Chiller (Inside

View)

Abbreviations and Symbols

Engine Design

G3508

Cylinder And Valve Location

Number And Arrangement Of Cylinders........................................................V–8

Valves Per Cylinder ...........................................4

Bore ...........................................170 mm (6.7 in)

Stroke.........................................190 mm (7.5 in)

Compression Ratio.....................refer to nameplate on engine

Type Of Combustion.....................spark ignited

Crankshaft Rotation (as viewed from flywheel end) ................counterclockwise

Firing Order ..................................1-2-7-3-4-5-6-8

Compression Ratios Available .................................8.1:1, 9.1:1, 11.0:1

Valve SettingInlet.....................................0.51 mm (.020 in)Exhaust ..............................1.27 mm (.050 in)

Note: Front of engine is opposite flywheelend. Left and right side of engine are as seenfrom flywheel end. No. 1 cylinder is frontcylinder on right side. No. 2 cylinder is frontcylinder on left side.

G3512


Number And Arrangement Of Cylinders......................................................V–12


Bore ...........................................170 mm (6.7 in)

Stroke.........................................190 mm (7.5 in)




Firing Order.................1-12-9-4-5-8-11-2-3-10-7-6

Compression Ratios Available .....................8.1:1, 9.1:1, 11.0:1, 12.0:1



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G3516


Number And Arrangement OfCylinders......................................................V–16


Bore ...........................................170 mm (6.7 in)

Stroke.........................................190 mm (7.5 in)




Firing Order ........1-2-5-6-3-4-9-10-15-16-11-12-13-14-7-8

Compression Ratios Available .....................8.1:1, 9.1:1, 11.0:1, 12.0:1



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Figure 1. Component Location(1) Ignition transformer (under valve cover). (2) Manifold air pressure sensor. (3) Detonation sensor. (4) Electronic Ignition System control module. (5) Speed/Timing sensor. (6) Wiring harness for Speed/Timing sensor(internal).

Electronic IgnitionSystem (EIS)

The Caterpillar Electronic Ignition System(EIS) is designed to replace the traditionalmagneto ignition system. The ElectronicIgnition System eliminates the magneto andother components that were subject tomechanical wear. It also provides increasedengine diagnostic and troubleshootingcapabilities.

The Electronic Ignition System (Figures 1)uses one control module (4) to handle manyapplications and many engine types. This isachieved by allowing the operator to changekey parameters “on–sight”. Theseprogrammable parameters are referred to asCustomer Specified Parameters and may beset or changed using the Digital DiagnosticTool (DDT). The values programmed into thesystem are stored in the EIS Control Modulememory. This allows the operator to tailor the

ignition system operation with a single servicetool.

The DDT (Digital Diagnostic Tool) servicetool is used to program Customer SpecifiedParameters, monitor engine functions, anddisplay engine diagnostics. The DDT canmonitor engine speed, engine timing anddetonation levels.

For additional information on programmingparameters and troubleshooting diagnosticcodes, refer to Electronic Troubleshooting,G3500 Engines, SENR6413.

The EIS control module also has the ability todiagnose and store system problems andpotential transformer secondary circuitproblems. When a problem is detected, adiagnostic code is generated and can bedisplayed on the DDT.

The EIS system monitors engine operationand distributes power to the cylindertransformers, to provide the best engineperformance at all engine speeds. It alsoprotects the engine from damage caused by

detonation. Within specified limits, control ofengine timing (retarding) is infinitely variable.

The Electronic Ignition System (Figure 3)provides detonation protection and precisionspark control for each cylinder. Detonation iscontrolled as it occurs and timing is retardedonly as much and as long as necessary toprevent engine damage. The EIS systemallows improved operation, economy andlower emission levels. The system consists ofthree basic groups: the control module,ignition transformers(2) and sensors.

EIS Control Module

Figure 2. Ignition System Components(1) Spark plug. (2) Ignition transformer. (3) Valve cover.(4) Wiring harness. (5) Electronic Ignition Systemcontrol module.

The EIS Control Module (5) is a sealed unitwith no serviceable parts (Figure 2). Thecontrol module monitors engine operationthrough a series of sensors. The sensors areconnected to the module through wiringharnesses (4) routed inside the engine block.The control module uses input from thesensors and the control panel settings to

determine ignition timing. The control moduleprovides system diagnostics and also suppliesvoltage to the ignition transformers (2) whichstep up the voltage to fire the spark plugs (1).The valve cover (3) acts as a ground for theignition transformer.

Engine timing is controlled by the EIS ControlModule. It is based on the desired enginetiming, customer specified parameters(programmed by the operator) and theconditions in which the engine operates. Theengine operator can change the maximumadvanced timing, the speed timing maps andload timing maps using the Digital DiagnosticTool (DDT). The EIS Control Moduleautomatically adjusts the engine timingaccording to the engine operating conditions,as determined by information from the enginespeed/timing sensor, manifold air pressuresensor, and detonation sensors.

The EIS Control Module has up to 16 ignitionoutputs to the ignition transformers. It alsouses sensors and internal circuitry to monitorthe system components. If a problem developsin a component or harness, the control willsense the problem and notify the operator bycreating a diagnostic code.

Ignition TransformersEach cylinder has an ignition transformerlocated under the cylinder valve cover. TheEIS Control Module sends a pulse to theprimary coil of the ignition transformer toinitiate combustion in each cylinder. Thetransformer steps up the voltage to create anarc across the spark plug gap. The sparkcreated by the arc, ignites the gas in thecylinder. On engines equipped with EIS, thecylinder valve cover acts as the ground for theignition transformer. Care should be exercisedwhen working on the engine with a valvecover removed. Always disconnect the primarylead to the transformer when a valve cover isremoved.

The ignition harness connects the EIS ControlModule to the individual ignitiontransformers. The ignition harness is routedinside the engine alongside the camshaft.

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Engine SensorsEngine sensors provide information to the EISControl Module that allow the module tocontrol the engine as efficiently as possibleover a wide range of operating conditions.

Detonation SensorsThe Detonation Sensors (RHDS and LHDS)monitor the engine for excessive detonation(vibration). One sensor is mounted in thecenter of each cylinder bank. The sensorproduces a voltage signal proportional toengine detonation. This information isprocessed by the EIS Control Module todetermine detonation levels and changesengine timing as needed.

Speed/Timing SensorThe Speed/Timing Sensor provides accuratespark timing information for the controlmodule. A speed/timing ring, mounted on therear, left camshaft, provides the signal patterndetected by the sensor and read by the controlmodule. The control module determinesengine speed and timing position from thesensor signal.

Manifold Air Pressure Sensor (Load Sensor)The Manifold Air Pressure Sensor providesengine load information to the EIS ControlModule. The sensor is connected to the inletmanifold. The information is processed by thecontrol module to determine engine timingand diagnostics.

Desired Timing ParameterThe Desired Timing Parameter allows thecustomer to electronically program theignition spark timing of the EIS System tomeet specific application/installation needs.The desired timing is programmed using theDDT Service Tool. The desired timing valuecan be changed while the engine is running orstopped. The value entered for the desiredtiming is the ignition timing when the engineis operating at rated speed, full load.

Note: Actual ignition timing at a giveninstance may vary from the desired timingvalue due to variations in engine speed,detonation activity or type of fuel being used.

Fuel, Air Inlet andExhaust Systems

Engine BasicsOn a four-stroke gas engine during the intakestroke, a change of fuel and air (mixed outsidethe combustion chamber in the carburetor) isdrawn (NA) or forced (TA) through the intakevalve (Figure 3). This mixture of fuel and air iscompressed on the compression stroke and isthen ignited by a spark. This spark isgenerated and timed by the ElectronicIgnition System (EIS). The piston is thenforced downward, creating the power stroke,toward bottom dead center by the expandinggases. On the exhaust stroke, the burnedgases are pushed out of the cylinder throughthe exhaust valve as the piston travels backtoward top dead center.

Diesel engines, like natural gas engines,operate in a slightly different way, althoughthe four strokes are the same. On the intakestroke, only air is drawn or forced into thecompression chamber. On the compressionstroke, the air is compressed and thereforeheated; just before the piston reaches top deadcenter, fuel is injected under high pressure.The fuel-air mixture will ignite by itself at thebeginning of the power stroke.

Diesel engines are typically limited by theircapabilities to carry structural load with peakpressures up to 10 335 kPa (1500 psi). Gasengines are limited by their capability to carrythermal load-high exhaust temperatures.

The gas engine runs with higher exhausttemperatures because it runs with a constantair-fuel ratio at any load. The diesel engineruns with an excess amount of air at any load.Only the amount of fuel burned increases with

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the load. This additional air also cools thecharge in diesel engines.

Figure 4. Fuel, Air Inlet And Exhaust SystemComponents (G3512 Engine Shown)(1) Balance line between carburetor and gas pressureregulator. (2) Carburetor. (3) Gas inlet line tocarburetor. (4) Aftercooler. (5) Exhaust bypass valve. (6) Exhaust elbow. (7) Turbocharger. (8) Gas pressureregulator. (9) Gas shutoff valve. (10) Air cleaner.

The components of the fuel, air inlet andexhaust system (Figure 4) control the quality,temperature and amount of air/fuel mixtureavailable for combustion. Some of thesecomponents are the gas inlet line (3), aircleaners (10), turbochargers (7), watercooledaftercooler (4), gas shutoff valve (9), gaspressure regulator (8), carburetor (2),turbulence chamber, distribution channel, aninlet manifold and the intake and exhaustvalve mechanisms. Two camshafts, one oneach side of the block, control the movementof the valve system components.

The inlet manifold is a series of elbows thatconnect the distribution channel (located inthe middle of the engine) to the inlet ports(passages) of the cylinder heads.

There is a separate air cleaner, turbochargerand watercooled exhaust manifold on eachside of the engine. The watercooled exhaustmanifolds provide a “gas tight” connectionfrom the cylinder heads to the turbochargers.The manifolds also serve as a water manifoldby collecting coolant from each cylinder headand directing it to the regulator housing.

All installations have a shutoff valve in the gassupply line. The shutoff valves are eitherEnergized To Run (ETR) or Energized ToShutoff (ETS). All engines with turbochargershave a balance line (1) between the gasshutoff valve and the carburetor.

In the Energized To Run system, power mustbe supplied to the shutoff valve to keep thefuel coming to the engine. To stop the engine,the power is removed from the shutoff valve,which interrupts the fuel to the engine.

In the Energized To Shutoff system, no poweris supplied to the shutoff valve to keep the fuelcoming to the engine. To stop the engine,power is supplied to the shutoff valve, whichinterrupts the fuel to the engine. The valvecan also be manually operated to stop theengine. After the engine is stopped, manualresetting of the valve is needed to start theengine.

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Figure 3. Four-stroke process.

Fuel SystemSeveral variations of fuel systems for G3500Engines are available to best suit theindividual customer installation. Althougheach installation may be different, the basiccomponents will be the same or similar. Twodifferent carburetor set-ups (low pressure andhigh pressure) are available that willdetermine the components of the rest of thefuel delivery system. The low pressure or highpressure carburetor set-ups may be used witheither the Standard (Stoichiometric) or LowEmission engines depending on the inletpressure of the fuel available to the engine.

Low Pressure Carburetor SystemTwo different gas pressure regulatorarrangements are generally used on enginesequipped with low pressure carburetors.Although the position and number ofcomponents may differ, both systems functionin a similar manner. One arrangement uses asingle gas pressure regulator (Figure 5) tosupply both carburetors. The regulator will belocated at the rear of the engine on acenterline between the turbochargers. Theother arrangement uses two gas pressureregulators (Figure 6), one for each carburetor.A regulator will be mounted on both sides ofthe engine near each carburetor.

Figure 5. Single Regulator Arrangement (1) Air cleaner. (2) Low pressure carburetor. (3) Turbocharger. (4) Gas inlet line. (5) Balance line. (6) Gas pressure regulator. (7) Gas pressure valveassembly.

Figure 6 Dual Regulator Arrangement (1) Air cleaner. (2) Low pressure carburetor. (3) Turbocharger. (4) Gas inlet line. (5) Balance line. (6) Gas pressure regulator.

From the main gas supply line, gas enters thegas pressure regulator (6). The gas pressureregulator is adjusted to provide a flow of fuel,at low pressure, to the engine gas inlet line(4). As the compressor wheels of theturbochargers (3) rotate, fuel (at lowpressure) is drawn through the fuel inlet linesto the carburetors (2). The carburetors (oneon each side of the engine) are locatedbetween the air cleaners (1) and thecompressor side of the turbochargers. Thecarburetors mix the fuel with inlet air from theair cleaners. The air/fuel mixture is pulledinto the turbochargers, compressed and sentto the aftercooler. The compressed, cooledair/fuel mixture flows from the aftercooler tothe throttle group. The throttle group isconnected by a linkage to the governor andcontrols the flow of the air/fuel mixture intothe inlet plenum. The air/fuel mixture in theinlet plenum enters the cylinder through thecylinder inlet valves where it is compressedand ignited by the spark plug.

Turbocharged engines have a balance line (5)connected between the carburetor air inletand the atmospheric vent of gas pressureregulator. The balance line directs carburetorinlet air pressure to the upper side of theregulator diaphragm to control gas pressure atthe carburetor. The inlet air pressure added tothe spring force on the diaphragm, makessure that gas pressure to the carburetor willalways be greater than inlet air pressure,regardless of load conditions. For example,under engine acceleration, the air pressure

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increases. A small amount of the increased airpressure is directed to the gas pressureregulator and moves the control to increasesupply gas pressure to the carburetor. By thismethod, the correct differential pressurebetween the gas pressure regulator and thecarburetor air inlet is controlled. Aturbocharged engine will not develop fullpower with the balance line disconnected.

Engines equipped with a single regulatorarrangement, have a gas pressure valveassembly located in the fuel inlet line. The gaspressure valve assembly is used to adjustemission levels at full load, rated speed.

High Pressure Carburetor SystemOn engines equipped with high pressurecarburetors (Figure 7) the gas pressureregulator (4) is usually located on the side ofthe engine, in line with the carburetor (1) andthrottle group.

Figure 7. High Pressure Carburetor (1) Carburetor. (2) Gas supply line to carburetor. (3) Balance line from gas pressure regulator vent to inletair pressure at carburetor. (4) Gas pressure regulator.

From the main fuel supply inlet, fuel entersthe gas pressure regulator. The pressureregulated fuel flows through the air/fuel ratio

control valve. The air/fuel ratio control valveis operated by the actuator and the controlvalve linkage. Gas goes from the air/fuel ratiocontrol valve through the gas supply line (2)and then into the carburetor. Air is drawn inthrough the air cleaners and into theturbochargers. The turbochargers compressthe air and send it to the aftercooler. Theaftercooler lowers the temperature of thecompressed air and the air enters thecarburetor. The carburetor mixes the fuel andthe air. The air/fuel mixture passes throughthe throttle and into the air inlet plenum. Thethrottle group is connected by a linkage to anEG-3P Actuator and controls the flow of theair/fuel mixture into the inlet plenum. Theair/fuel mixture in the inlet plenum enters thecylinder through the cylinder intake valveswhere it is compressed and ignited by thespark plug.

Turbocharged engines have a balance line (3)connected between the carburetor air inletand the atmospheric vent of the gas pressureregulator. The balance line directs carburetorinlet air pressure to the upper side of theregulator diaphragm to control gas pressure atthe carburetor. The inlet air pressure added tothe spring force on the diaphragm, makessure that gas pressure to the carburetor willalways be greater than inlet air pressure,regardless of load conditions. For example,under engine acceleration, the air pressureincreases. A small amount of the increased airpressure is directed to the gas pressureregulator and moves the control to increasesupply gas pressure to the carburetor. By thismethod, the correct differential pressurebetween the gas pressure regulator and thecarburetor air inlet is controlled. Aturbocharged engine will not develop fullpower with the balance line disconnected.

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Gas Pressure Regulator

Figure 8 Regulator Operation (1) Spring side chamber. (2) Adjustment screw. (3) Spring. (4) Outlet. (5) Valve disc. (6) Main orifice. (7) Main diaphragm. (8) Lever side chamber. (9) Lever.(10) Pin. (11) Valve stem. (12) Inlet.

The function of the gas pressure regulator isto maintain a set pressure differential betweenthe outlet of the gas pressure regulator(connected to the carburetor fuel inlet) andthe carburetor air inlet. G3500 Engines can beequipped with different regulators to use avariety of fuels and a wide range of gaspressures and BTU ratings. The constructionand position on the engine may vary, but allfunction on similiar principles and work tomaintain an adjusted pressure differential.The following is a description of operation fora high pressure, high BTU content fuelregulator.

Gas goes through the inlet (12), main orifice(6), valve disc (5), and the outlet (4). Outletpressure is felt in the chamber (8) on the leverside of diaphragm (7).

As gas pressure in chamber (8) becomeshigher than the force of the diaphram spring(3) and air pressure in the spring sidechamber (1) (atmosphere on naturallyaspirated engines; turbocharger boost onturbocharged engines), the diaphragm ispushed against the spring. This turns thelever (9) at pin (10) and causes the valve stem(11) to move the valve disc to close the inletorifice.

With the inlet orifice closed, gas is pulled fromthe lever side of chamber (8) through theoutlet. This gives a reduction of pressure inthe chamber (8). As a result the pressurebecomes less than pressure in the spring sidechamber. Force of spring and air pressure inthe chamber on the spring side moves thediaphragm toward the lever. This turns(pivots) the lever and opens the valve disc,permitting additional gas flow to thecarburetor.

Carburetor

Figure 9. Carburetor Operation (1) Cover. (2) Diaphragm. (3) Spring. (4) Air valve. (5) Air valve body. (6) Gas inlet body. (7) Gas valve. (8) Power screw. (9) Plate. (10) Throttle plate.

Note: Operation of a carburetor (Figure 9)with a single air valve is described. Operationof carburetors with dual air valves is the same.

Atmospheric air goes through the air cleanersto the air horn of the carburetor on naturallyaspirated engines. On turbocharged engines,the air is pulled through the air cleaners to theturbochargers and then pushed through anaftercooler core to the carburetor air horn. Inthe air horn, air goes around the air valvebody (5) and pushes on diaphragm (2) andthen goes down through the center of air valve

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(4), around gas inlet body (6), by throttle plate(10) into the engine.

Fuel goes into the carburetor at the center,through the gas inlet body. The fuel flows outthe top of the gas inlet body to mix with the airand then flows around the gas inlet body, bythe throttle plate into the engine. Gas valve (7)is connected to the air valve and is designed tolet the correct amount of fuel into thecarburetor at any opening of the air valvebetween idle and full load. Thus, at low idle,the gas valve keeps fuel flow to a minimumand gives a lean air fuel mixture. As theengine speed and load is increased, the gasvalve lets more fuel flow to give a richer airfuel mixture. When the engine is stopped, thespring holds the gas valve down against thevalve seat in the closed position and no fuelcan enter the carburetor. Power screw (8) andplate (9) control fuel inlet at full loadconditions when the gas valve is at amaximum distance off its seat.

As the engine is started, the intake strokes ofthe pistons cause a vacuum in the cylinderswhich causes a low pressure condition belowthe carburetor. Passages in air valve body (5)connect the low pressure to the upper side ofthe diaphragm. At this point, atmosphericpressure pushes up on the diaphragm and liftsit against the downward force of the spring.The air valve is connected to and pulled up bythe diaphragm. At this point, air can pushupward against the outside of the air valve tohelp lift it. The gas valve is connected to theair valve and is also lifted off its seat to let fuelenter the carburetor. The air pushes up on thediaphragm and at the same time goes aroundthe outside and inside of the air valve andaround the gas inlet body. As the air passesaround the gas inlet body, it mixes with thefuel. The air/fuel mixture then goes down bythe throttle plate, into the distributionchannels, to the inlet manifolds and then intothe cylinders for combustion.

2301A Electric GovernorThe 2301A Electric Governor Control Systemconsists of the components that follow: 2301AElectric Governor Control (EGC) , Actuator,Magnetic Pickup.

Figure 10. 2301A Electric Governor Control (EGC)

The 2301A Electric Governor System givesprecision engine speed control. The 2301Acontrol(Figure 10) measures engine speedconstantly and makes necessary correctionsto the engine fuel setting through an actuatorconnected to the fuel system.

The engine speed is felt by a magnetic pickup(Figure 11). This pickup is a single pole,permanent magnet generator made of wirecoils (2) around a permanent magnet polepiece. (4). See Figure 12. As the teeth of theflywheel ring gear (5) cut through themagnetic lines of force (1) around the pickup,an AC voltage is generated. The frequency ofthis voltage is directly proportional to enginespeed.

Figure 11. Magnetic Pickup Location(1) Magnetic pickup. (2) Flywheel housing.

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This engine speed frequency signal (AC) issent to the 2301A Control Box where aconversion is made to DC voltage. The DCsignal is now sent on to control the actuator,and this voltage is inversely proportional toengine speed. This means that if engine speedincreases, the voltage output to the actuatordecreases. When engine speed decreases, thevoltage output to the actuator increases.

Figure 12. Schematic Of Magnetic Pickup(1) Magnetic lines of force. (2) Wire coils. (3) Gap. (4) Pole piece. (5) Flywheel ring gear.

The actuator ((Figure 13) changes theelectrical input from the 2301A Control to amechanical output that is connected to the fuelsystem by linkage. For example, if the enginespeed is more than the speed setting, the2301A Control will decrease its output and theactuator will now move the linkage todecrease the fuel to the engine.

Figure 13. EG3P Actuator(3) Actuator. (4) Actuator lever.

Woodward PSG GovernorsThe Woodward PSG (Pressure compensatedSimple Governor) can operate as anisochronous or a speed droop type governor.It uses engine lubrication oil, increased to apressure of 1200 kPa (175 psi) by a gear typepump inside the governor, to givehydra/mechanical speed control.

The governor (Figure 15) is driven by thegovernor drive unit. This unit turns pilot valvebushing (13) clockwise as seen from the driveunit end of the governor (Figure 14). The pilotvalve bushing is connected to a spring drivenballhead. Flyweights (7) are fastened to theballhead by pivot pins. The centrifugal forcecaused by the rotation of the pilot valvebushing causes the flyweights to pivot out.This action of the flyweights changes thecentrifugal force to axial force against speederspring (5). There is a thrust bearing (9)between the toes of the flyweights and theseat for the speeder spring. Pilot valve (12) isfastened to the seat for the speeder spring.Movement of the pilot valve is controlled bythe action of the flyweights against the force ofthe speeder spring.

The engine is at the governed (desired) rpmwhen the axial force of the flyweights is thesame as the force of compression in thespeeder spring. The flyweights will be in theposition shown. Control ports (14) will beclosed by the pilot valve.

When the force of compression in the speederspring increases (operator increases desiredrpm) or the axial force of the flyweightsdecreases (load on the engine increases) thepilot valve will move in the direction of thedrive unit. This opens the control ports(14).Pressure oil flows through a passage in thebase to chamber (B). The increased pressurein the chamber causes power piston (6) tomove. The power piston pushes strutassembly (4), that is connected to output shaftlever (3). The action of the output shaft levercauses counterclockwise rotation of outputshaft (2). This moves carburetor controllinkage (15) in the THROTTLE OPENEDdirection (Figure 15).

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Figure 14. Schematic Of PSG Governor(1) Return spring. (2) Output shaft. (3) Output shaft lever. (4) Strut assembly. (5) Speeder spring. (6) Power piston. (7) Flyweights. (8) Needle valve. (9) Thrust bearing. (10) Pilot valve compensating land. (11) Buffer piston. (12) Pilot valve. (13) Pilot valve bushing. (14) Control ports. (A) Chamber. (B) Chamber.

Figure 15. PSG Governor Installed(2) Output shaft. (15) Carburetor control linkage.

As the power piston moves in the direction ofreturn spring (1) the volume of chamber (A)increases. The pressure in the chamberdecreases. This pulls the oil from the chamberinside the power piston, above buffer piston(11) into the chamber (A). As the oil movesout from above the buffer piston to fill thechamber the buffer piston moves up in thebore of the power piston. Chambers (A and B)are connected respectively to the chambersabove and below the pilot valve compensatingland (10). The pressure difference felt by thepilot valve compensating land adds to the axialforce of the flyweights to move the pilot valveup and close the control ports. When the flowof pressure oil to chamber (B) stops so doesthe movement of the fuel control linkage.

When the force of compression in the speederspring decreases (operator decreases desiredrpm) or the axial force of the flyweightsincreases (load on the engine decreases) thepilot valve will move in the direction of thespeeder spring. This opens the control ports.Oil from chamber (B) and pressure oil fromthe pump will dump through the end of thepilot valve bushing. The decreased pressure inchamber (B) will let the power piston move inthe direction of the drive unit. The returnspring pushes against the strut assembly. Thismoves the output shaft lever. The action of theoutput shaft lever causes clockwise rotation ofthe output shaft. This moves the carburetorcontrol linkage in the THROTTLE CLOSEDdirection, (Figure 15).

On PSG governors not equipped with electricspeed adjustment (Figure 16), speed can beadjusted with screw (1). When the screw is

turned clockwise it pushes the link assembly(2) against speeder spring (3). This causes anincrease in the force of speeder spring andpilot valve (4) will move toward governordrive unit. The engine will increase speed untilit gets to the desired rpm. When the screw isturned counterclockwise the link assemblymoves away from speeder spring. This causesa decrease in the force of the speeder springand the pilot valve will move away fromgovernor drive unit. The engine will decreasespeed until it gets to the desired rpm.

Figure 16. Non-electric PSG Governor (1) Screw. (2) Link assembly. (3) Speeder spring. (4) Pilot valve.

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Engines with non-electric governors are alsoequipped with a governor control group(Figure 17) to allow easier speed adjustment.

Figure 17. Governor Control Group(5) Positive lock lever. (6) Link assembly lever. (7) Governor.

As lever (5) is moved toward governor (7),linkage causes lever (6) to move in the samedirection. The link assembly lever is clampedto the shaft of the link assambly (2). As theshaft rotates, the link assembly pushes againstspeeder spring (3). This causes pilot valve (4)to move toward the governor drive unit. Theengine will increase speed until it gets todesired rpm.

When lever (5) is moved away from thegovernor, the link assembly lever moves in thesame direction. This causes the link assemblyto move away from the speeder spring. Thepilot valve then moves away from thegovernor drive unit and engine speeddecreases until desired rpm is reached.

Figure 18 PSG Electric-Type Governor(8) Synchronizing motor. (9) Clutch assembly. (10) Link assembly. (11) Speeder spring. (12) Pilot valve.

On electric type PSG governors (Figure 18),speed adjustments are made by a 24V DCreversible synchronizing motor (8). Themotor is controlled by a switch that can be putin a remote location.

The synchronizing motor drives clutchassembly (9). The clutch assembly protectsthe motor if it is run against the adjustmentstops.

When the clutch assembly is turned clockwiseit pushes link assembly (10) against speederspring (11). The force of compression in thespeeder spring is increased. This causes thepilot valve (12) to move toward the governordrive unit. The engine will increase speed,then get stability at a new desired rpm.

When the clutch assembly is turnedcounterclockwise the link assembly movesaway from the speeder spring. The force ofcompression in the speeder spring isdecreased. This causes the pilot valve to moveaway from the governor drive unit. The enginewill decrease speed, then get stability at a newdesired rpm.

Note: The clutch assembly can be turnedmanually if necessary.

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Speed droop is the difference between no loadrpm and full load rpm. This difference in rpmdivided by the full load rpm and multiplied by100 is the percent of speed droop.

No load speed – Full load speed 3 100

Full load speed

5% of speed droop

Figure 19. PSG Governor (View A-A from Figure 18)(10) Link assembly. (13) Pivot pin. (14) Output shafts.(15) Droop adjusting bracket. (16) Shaft assembly.

The speed droop of the PSG governor can beadjusted. The governor is isochronous when itis adjusted so that the no load and full loadrpm is the same. Speed droop permits loaddivision between two or more engines thatdrive generators connected in parallel orgenerators connected to a single shaft.

Speed droop adjustment on PSG governors(Figure 19) is made by movement of pivotpin (13). When the pivot pin is put inalignment with output shafts (14), movementof the output shaft lever will not change theforce of the speeder spring. When the force ofthe speeder spring is kept constant, thedesired rpm will be kept constant. When thepivot pin is moved out of alignment with theoutput shafts, movement of the output shaftlever will change the force of the speederspring proportional to the load on the engine.When the force of the speeder spring ischanged, the desired rpm of the engine willchange.

An adjustment bracket (15) outside thegovernor connected to the pivot pin by thelink assembly and shaft assembly (16) is usedto adjust speed droop.

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Air flow is the same on both sides of theengine. See Figure 21. Clean inlet air from theair cleaners is pulled through theturbocharger compressor housing (1) by acompressor wheel (Figure 20). Rotation of thecompressor wheel causes compression of theair and forces it through lines to theaftercooler (2). The aftercooler lowers thecompressed air temperature and provides airat a constant temperature to the carburetor (3)for maximum air/fuel ratio control,independent of load on the engine. Theaftercooler is usually watercooled, but air-to-air aftercooling can be used.

From the aftercooler the air goes through thecarburetor (where it mixes with gas) and theninto a turbulence chamber (4) which keepsthe air and fuel mixed. A distribution channel(5) is located below the turbulence chamberand has holes in it to direct an equal air/fuelmixture at a constant temperature to each

cylinder head (6) inlet port. Air flow from theinlet ports into the cylinder combustionchamber is controlled by the intake valves.

There are two intake and two exhaust valvesfor each cylinder. Make reference to ValveSystem Components. The intake valves openwhen the piston moves down on the intakestroke. The cooled, compressed air/fuelmixture from the inlet port is pulled into thecylinder. The intake valves close and thepiston starts to move up on the compressionstroke. When the piston is near the top of thecompression stroke, the Electronic IgnitionSystem control module sends voltage througha transformer to the spark plug. Thetransformer increases the voltage until a sparkis created across the plug gap. The sparkignites the air/fuel mixture and combustionstarts. The force of combustion pushes thepiston down on the power stroke. When thepiston moves up again it is on the exhaust

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Figure 20. Air Inlet System(1) Turbochargers. (2) Aftercooler. (3) Carburetor. (4) Turbulence chamber. (5) Distribution channel. (6) Cylinder head.

Air Inlet And Exhaust Systems

stroke. The exhaust valves open and theexhaust gases are pushed through theexhaust port into the exhaust manifolds (8).See Figure 21. After the piston completes theexhaust stroke, the exhaust valves close andthe cycle (intake, compression, power,exhaust) starts again.

Figure 21. Exhaust System(7) Exhaust elbow. (8) Exhaust manifold.

Exhaust gases from the exhaust manifolds gointo the turbine side of each turbocharger andcause a turbine wheel to turn. The turbinewheel is connected to the shaft that drives thecompressor wheel. The exhaust gases then goout the exhaust outlet through the exhaustelbow (7). Changes in engine load and fuelburned cause changes in rpm of the turbineand compressor wheels. As the turbochargerair pressure boost increases, the ratio of air tofuel can change. To increase air and gasdensities equally during increased boost, abalance line is connected between thecarburetor air inlet and the atmospheric ventof the gas pressure regulator.

Aftercooler

Figure 22. Engine With Watercooled Aftercooler(1) Aftercooler. (2) Coolant return line. (3) Water pump.

The aftercooler (Figure 23) is located in theair lines between the turbochargers and thecarburetor. The aftercooler is usuallywatercooled (Figure 22) but can be an air toair type.

Watercooled aftercoolers (1) have a separatecircuit cooling system, from the engine jacketwater cooling system. Coolant is supplied tothe water pump (3). The water pump sendscoolant through the coolant inlet line into thebottom of the aftercooler. It then flowsthrough the core assembly and back out of theaftercooler through coolant return line (2) tothe thermostatic valve that is installed in thecoolant return line, to keep coolant in theaftercooler core assembly at the correcttemperature.

Air flow through both cooling systems is asfollows. Inlet air from the compressor side ofthe turbochargers flows into the aftercoolerthrough pipes. This air then passes throughthe aftercooler core assembly which lowersthe temperature. The cooler air (mixed withfuel on low pressure carburetor engines) goesout of the aftercooler into the carburetor. Fuelis mixed with the inlet air (on enginesequipped with high pressure carburetors).The air/fuel mixture goes through theturbulence chamber and distribution channeland up through the elbows to the intake ports(passages) in the cylinder heads. The mixturegoes through the intake valves into thecombustion chambers.

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Figure 23. Distribution Channel And Air Chamber Drain(4) Drain plug.

All engines have two drain plugs (4) installed(Figure 23). One drain plug is located betweenthe No. 1 and No. 3 cylinder heads, andanother plug is located between the last twocylinder heads on the left side of the engine.These plugs can be removed to check forwater or coolant in the cylinder block airchamber.

Air to air aftercooled systems (Figures 24–26)contain a temperature controller that ispressurized to keep dirt and moisture out of itand a bypass valve which consists of anactuator and valve positioner (5). Thetemperature controller (12) monitors inlet airtemperature and is adjusted to keep it at 43°C(110°F). If the air temperature is too cold, thetemperature controller signals an actuator(with pneumatic or gas pressure) to bypassthe aftercooler core so air flows from theturbochargers (8) directly into the carburetor(7).

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Figure 24. Schematic Of An Air To Air Aftercooler Engine(5) Actuator with valve positioner. (6) Air cleaner. (7) Carburetor. (8) Turbocharger. (9) Cooling unit.

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Figure 25. Typical Air To Air Aftercooled System(5) Actuator with valve positioner. (6) Air cleaner. (7) Carburetor. (10) Vent cap for temperature controller. (11) Sensing element for temperature controller. (12) Temperature controller.

TurbochargersOn turbocharged engines there are twoturbochargers (Figures 27 and 28), on therear of the engine. Each turbocharger has aturbine wheel (exhaust side) and acompressor wheel (inlet side). The twowheels are mounted on a common shaft andturn together. The turbine side of theturbochargers is fastened to the exhaustmanifolds. The compressor side of theturbocharger is connected to the aftercooler.

Figure 27. Turbochargers(1) Turbocharger inlet. (2) Oil inlet line. (3) Water cooled turbine housing. (4) Exhaust bypassvalve. (5) Oil drain line.

Exhaust gases are regulated by the exhaustbypass valve (4). The exhaust gas enters theturbine housing (3) and pushes against theblades of the turbine wheel (10). The turbinewheel is connected to the same shaft as thecompressor wheel. Rotation of the turbinewheel causes the compressor wheel to turn.

At high idle, the shaft can rotate at speeds upto 70,000 rpm.

Figure 28. Turbocharger(6) Compressor wheel. (7) Bearing. (8) Oil inlet. (9) Bearing. (3) Turbine housing. (10) Turbine wheel.(1) Air inlet. (11) Oil outlet.

Clean air from the air cleaners is pulledthrough the compressor housing air inlet (1)by rotation of compressor wheel (6). Theaction of the compressor wheel blades causesa compression of the inlet air. Thiscompression gives the engine more powerbecause it makes it possible for the engine toburn additional fuel with greater efficiency.

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Figure 26. Schematic Of Instrument Installation For Air To Air Aftercooled Systems

Maximum rpm of the turbocharger iscontrolled by the fuel setting, the high idlerpm setting and the height above sea level atwhich the engine is operated.

NOTICEIf the high idle rpm or the fuel setting ishigher than given in the Fuel SettingInformation Fiche (for the height above sealevel at which the engine is operated), therecan be damage to engine or turbochargerparts. Damage will result when increased heatand/or friction due to the higher engineoutput goes beyond the engine cooling andlubrication systems abilities. A mechanic thathas the correct training is the only one tomake the adjustment of fuel setting and highidle rpm setting.

The bearings (7 and 9) in the turbochargeruse engine oil under pressure for lubrication.The oil comes in through oil inlet port (8) andgoes through passages in the center sectionfor lubrication of the bearings. Then the oilgoes out oil outlet port (11) and back to the oilpan.

Exhaust Bypass Valve (Engines WithTurbochargers)G3500 Engines equipped with turbochargersare also equipped with an adjustable exhaustbypass valve (Figures 29 and 30). The bypassvalve can be adjusted for altitude conditions orto adjust the throttle angle for a given load. Ahigh throttle angle at maximum load willreduce resistance to flow by the throttle plateand minimize fuel consumption.

Figure 29. Exhaust Bypass Valve Location(1) Exhaust bypass valve (2) Exhaust elbow. (3) Turbocharger turbine housing. (4) Water cooledvalve guide housing. (5) Control line from aftercooler toexhaust bypass valve.

The control line from the aftercooler to theexhaust bypass valve (5) connects thecompressor side of the turbocharger (throughthe aftercooler) with the exhaust bypass valve.The exhaust bypass valve (1) is connectedthrough the waste gate housing to the exhaustelbow (2). The bypass valve controls theamount of exhaust gases that enter theturbocharger turbine housing (3) and drivethe turbine wheel, or bypass the turbine andgo out the exhaust elbow. The guide housing(4) for the bypass valve is water cooled.

Figure 30. Exhaust Bypass Valve Operation(5) Control line connection. (6) Springs. (7) Cover assembly. (8) Poppet valve. (9) Breatherlocation. (10) Guide (base) assembly. (11) Diaphragm.(12) Diaphragm retainer.

Poppet Valve (8) is activated directly by apressure differential between the air pressure(atmosphere) and the turbochargercompressor outlet pressure to the aftercooler.

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One side of the diaphragm (11) in theregulator feels atmospheric pressure througha breather (9) in the top of the regulator. Theother side of the diaphragm feels air pressurefrom the outlet side of the turbochargercompressor through the control lineconnected to the aftercooler. When outletpressure to the aftercooler gets to the correctvalue, the force of the air pressure moves thediaphragm and overcomes the force of thesprings (6) and atmospheric pressure. Thisopens the poppet valve, and allows a portion ofthe exhaust gases to bypass the turbine wheel.The guide (10) for the poppet valve is watercooled.

Under constant load conditions, the valve willtake a set position, permitting just enoughexhaust gas to go to the turbine wheel to givethe correct air pressure to the aftercooler.

The Exhaust Bypass Valve is preset at thefactory. Adjustments may be necessary due toaltitude or changes in ambient temperatureconditions.

Valve System Components

Figure 31. Valve System Components(1) Rocker arm. (2) Bridge. (3) Rotocoil. (4) Valve spring. (5) Push rod. (6) Lifter.

The valve system components (Figure 31)control the flow of inlet air and exhaust gasesinto and out of the cylinders during engineoperation.

The crankshaft gear drives the camshaft gearsthrough idlers. Both camshafts must be timedto the crankshaft to get the correct relationbetween piston and valve movement.

The camshafts have two cam lobes for eachcylinder. The lobes operate the valves.

As each camshaft turns, the lobes on thecamshafts cause lifters (6) to move up anddown. This movement makes push rods (5)move rocker arms (1). Movement of therocker arms makes bridges (2) move up anddown on dowels in the cylinder head. Thebridges let one rocker arm open and close twovalves (intake or exhaust). There are twointake and two exhaust valves for eachcylinder.

Rotocoils (3) cause the valves to turn whilethe engine is running. The rotation of thevalves keeps the deposit of carbon on thevalves to a minimum and gives the valveslonger service life.

Valve springs (4) cause the valves to closewhen the lifters move down.

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This system (Figures 32–36) uses an oil pump(14) with three pump gears that are driven bythe front gear train. Oil is pulled from the panthrough suction bell (16) and elbow (15) bythe oil pump. The suction bell has a screen toclean the oil.The oil pump pushes oil through oil cooler(11) and the oil filters to oil galleries (1 and 2)in the block. The fin and tube type oil coolerlowers the temperature of the oil before the oilis sent on to the filters.

Bypass valve (12) allows oil flow directly to thefilters if the oil cooler becomes plugged or ifthe oil becomes thick enough (cold start) toincrease the oil pressure differential (coolerinlet to outlet) by an amount of 180 ± 20 kPa(26 ± 3 psi).

Note: In certain cogeneration models, withhigh water temperatures, an oil temperatureregulator (instead of the oil cooler bypassvalve) is used in the line going to the oil filter.When the oil is thick (cold start) the oiltemperature regulator lets oil flow directly tothe filters. When the oil temperature regulatoropens (engine warm) the oil is sent throughthe oil cooler to the oil filters.

Cartridge type filters are located in oil filterhousing (17) at the front of the engine. Asingle bypass valve is located in the oil filterhousing.

Clean oil from the filters goes into the blockthrough adapter (9). Part of the oil goes to the

Figure 32. Lubrication System Schematic(1) Main oil gallery. (2) Left camshaft oil gallery. (3) Piston cooling jet oil gallery. (4) Piston cooling jet oil gallery. (5) Right camshaft oil gallery. (6) Turbocharger oil supply. (7) Sequence valve. (8) Sequence valve. (9) Adapter. (10) Oil filter bypass valve. (11) Oil cooler. (12) Bypass valve. (13) Oil pump relief valve. (14) Engine oil pump. (15) Elbow. (16) Suction bell. (17) Oil filter housing.

Lubrication System

left camshaft oil gallery (2) and part goes tothe main oil gallery (1).

The camshaft oil galleries are connected toeach camshaft bearing by a drilled hole. Theoil goes around each camshaft journal,through the cylinder head and rocker armhousing, to the rocker arm shaft. A drilledhole connects the bores for the valve lifters tothe oil hole for the rocker arm shaft. The valvelifters get lubrication each time they go to thetop of their stroke.

The main oil gallery is connected to the mainbearings by drilled holes. Drilled holes in thecrankshaft connect the main bearing oilsupply to the rod bearings. Oil from the rearof the main oil gallery goes to the rear of rightcamshaft gallery (5).

Sequence valves (7 and 8) let oil from main oilgallery go to piston cooling jet oil galleries (3and 4). The sequence valves open at 140 kPa(20 psi). The sequence valves will not let oilinto the piston cooling jet oil galleries untilthere is pressure in the main oil gallery. Thisdecreases the amount of time necessary forpressure build-up when the engine is started.It also helps hold pressure at idle speed.

Figure 33. Piston Cooling And Lubrication (18) Cooling jet.

There is a piston cooling jet (18) below eachpiston. See Figure 33. Each cooling jet has twoopenings directed at the center of the piston.This helps cool the piston and giveslubrication to the piston pin.

Figure 34. Turbocharger(6) Oil supply line. (19) Oil drain lines for turbocharger.

Oil lines (6) supply oil to the turbochargers(Figure 34). The turbocharger drain lines (19)are connected to the flywheel housing on eachside of the engine.

Oil is sent to the front and rear gear groupsthrough drilled passages in the front and rearhousings and cylinder block faces. Thesepassages are connected to camshaft oilgalleries (2 and 5).

After the oil for lubrication has done its work,it goes back to the engine oil pan.

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Figure 35. Right Front Side Of Engine(10) Oil filter bypass valve. (17) Oil filter housing. (21) Oil line to filter housing.

Figure 36. Left Front Of Engine(9) Adapter. (17) Oil filter housing. (22) Oil outlet linefrom oil filter housing.

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Cooling System

Jacket Water System

Figure 37. Right Side Of Engine (1) Water line to front of engine cylinder block. (2) Coolant inlet. (3) Oil cooler. (4) Water pump.

This system (Figure 37 & 38) uses a waterpump (4) that is driven by the lower frontright gear group. Coolant from a radiator orother heat exchanger is pulled into the coolantinlet (2) in the center of the water pumphousing by the rotation of the water pumpimpeller. The coolant flow is then divided atthe water pump outlet. Part of the coolant flowis sent through water line (1) to the front ofthe cylinder block and part is sent through theengine oil cooler (3).

Note: There is one opening on the pumpoutlet so that a remote pump can beconnected to the system. The remote pumpcan be used if there is a failure of the waterpump on the engine.

Coolant is sent through a water line to thefront of the cylinder block and through a maindistribution manifold to each cylinder waterjacket. The main distribution manifold islocated just above the main bearing oil galleryin the center of the cylinder block. Some ofthe coolant goes out the back of the cylinderblock and into the adapter housing for theexhaust bypass valve. Flow from the exhaustbypass valve adapter housing is divided. Partof the coolant goes up through the exhaustelbow and part goes up through theturbocharger turbine housings. All coolant

flow is then directed into the water cooledexhaust manifolds.

The coolant sent to the oil cooler goesthrough the oil cooler and flows into the waterjacket of the block at the right rear cylinder.The cooler coolant mixes with the hottercoolant and goes to both sides of the blockthrough the distribution manifolds connectedto the water jacket of all the cylinders.

Figure 38. Coolant Flow From Rear of Engine(5) Exhaust elbow. (6) Water line between exhaustelbow and exhaust manifold. (7) Water line betweenexhaust bypass valve guide and exhaust elbow. (8) Water cooled exhaust manifold. (9) Water linebetween exhaust manifold and turbocharger turbinehousing.

The coolant flows up through the waterjackets and around the cylinder liners fromthe bottom to the top. Near the top of thecylinder liners, where the temperature is thehottest, the water jacket is made smaller. Thisshelf (smaller area) causes the coolant to flowfaster for better liner cooling. Coolant fromthe top of the liners goes into the cylinderhead which sends the coolant around theparts where the temperature in the cylinderhead is the hottest. Coolant then goes to thetop of the cylinder head and out through anelbow, one at each cylinder head, into thewatercooled exhaust manifolds (8) (Figure 43)at each bank of cylinders. Coolant from theexhaust manifolds flows through lines (9) tocool the turbine side of the turbochargers.Coolant flows through line (6) to cool theexhaust elbow (5). Coolant flows through line(7) from the top of the cylinder block, coolsthe exhaust bypass valve guide and flows intothe exhaust elbow. After cooling enginecomponents the coolant flow is directed

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through the exhaust manifolds to thetemperature regulator (thermostat) housing.

The water temperature regulator housing islocated at the top, front of the engine. It has anupper and lower flow section, and uses fourtemperature regulators. The sensing bulbs ofthe four temperature regulators are in thecoolant in the lower section of the housing.Before the engine reaches operatingtemperatures and the regulators open, coldcoolant is sent through the lower section ofthe housing and through the bypass line backto the inlet of the water pump. As thetemperature of the coolant increases enoughto make the regulators start to open, coolantflow in the bypass line is stopped and coolantis sent through the outlets to the radiator orheat exchanger.

Note: The water temperature regulator is animportant part of the cooling system. Itdivides coolant flow between the heatexchanger and internal bypass of the waterpump as necessary to maintain the correcttemperature. If the water temperatureregulator is not installed in the system, thereis no mechanical control, and most of thecoolant will take the path of least resistancethrough the bypass. This will cause the engineto overheat in hot weather. In cold weather,even the small amount of coolant that goesthrough the radiator is too much, and theengine will not get to normal operatingtemperatures.

Total system coolant capacity will depend onthe size of the heat exchanger. Use a coolantmixture of 50 percent pure water and 50percent permanent antifreeze, then add aconcentration of 3 to 6 percent corrosioninhibitor.

Separate Circuit Aftercooler(SCAC) System

Figure 39. Left Side Of Engine(1) Aftercooler. (2) Coolant return line. (3) AuxiliaryWater pump.

Engines with a water cooled aftercooler, use aseparate circuit aftercooler (SCAC) systeminstead of the normal jacket water circuit, tocool the air in the aftercooler. With the SCACsystem, coolant is supplied from a separateradiator or heat exchanger.

With the engine running at less thanoperating temperature, the aftercooler coolantcircuit is closed. The auxiliary water pump (3)sends coolant through a line to the aftercooler(1) at approximately 570 liter/m (150 U.S.gpm) (Figure 39). Coolant flows up throughthe core assembly and out of the aftercoolerthrough the coolant return line (2), through athermostatic valve and back to auxiliary waterpump. As the coolant temperature increases,the thermostatic valve opens and coolant flowfrom the aftercooler core assembly is directedto a radiator or heat exchanger and then backto auxiliary water pump. The thermostaticvalve will be fully open when the coolanttemperature is 32°C (90°F) or 54°C (130°F)depending on the thermostat installed in thevalve housing.

Note: Certain cogeneration engines do notuse thermostats to control jacket watertemperature. The engine temperature iscontrolled externally with a heat exchanger bymaintaining the outlet temperature of thesteam system. In high water temperatureapplications the oil cooler is on a separatecircuit. A thermostat controls the oiltemperature going to the bearings.

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Figure 40. G3500 Cooling System Engine SchematicTwo circuit with two engine driven pumps(1) Thermostatic valve (coolant temperature for aftercooler). (2) Heat exchanger (aftercooler). (3) Pump [aftercoolercircuit (engine driven)]. (4) Bypass line (aftercooler). (5) Front housing. (6) Aftercooler. (7) Regulator housing. (8) Bypass line (jacket water). (9) Oil cooler. (10) Pump [jacket water/oil cooler circuit (engine driven)]. (11) Heat exchanger (jacket water/oil cooler).

Figure 41. G3500 Landfill Cooling System Engine SchematicTwo circuit with two engine driven pumps (requires a large aftercooler/oil cooler heat exchanger).(1) Thermostatic valve. (2) Aftercooler/oil cooler heat exchanger. (3) Pump [aftercooler/oil cooler circuit (enginedriven)]. (4) Bypass line. (5) Front housing. (6) Regulator housing. (7) Aftercooler. (8) Thermostatic valve (oiltemperature). (9) Bypass line. (10) Oil cooler. (11) Pump [jacket water circuit (engine driven)]. (12) Heat exchanger(jacket water).

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Figure 42. G3500 Cogeneration Cooling System Engine SchematicJacket water pump (customer supplied)Three circuit with two engine driven pumps.(1) Thermostatic valve. (2) Heat exchanger (aftercooler). (3) Pump [aftercooler circuit (engine driven)]. (4) Bypass line (aftercooler). (5) Front housing. (6) Oil line to oil filter. (7) Aftercooler. (8) Regulator housing. (9) Bypass line (oil cooler). (10) Thermostatic valve (oil temperature). (11) Oil cooler. (12) Pump [oil cooler circuit(engine driven)]. (13) Pump [jacket water circuit (customer supplied)]. (14) Heat exchanger (jacket water).

Figure 43. G3500 Cogeneration Cooling System Engine SchematicJacket water pump (customer supplied)Two circuit with one engine driven pump (requires a large aftercooler/oil cooler heat exchanger).(1) Thermostatic valve (coolant temperature for aftercooler). (2) Aftercooler/oil cooler heat exchanger. (3) Pump [aftercooler/oil cooler circuit (engine driven)]. (4) Bypass line. (5) Front housing. (6) Regulator housing. (7) Aftercooler. (8) Thermostatic valve (oil temperature). (9) Bypass line. (10) Oil cooler. (11) Pump [jacket watercircuit (customer supplied)]. (12) Heat exchanger (jacket water).

Basic Block

Cylinder Block, Liners AndHeadsThe cylinders in the left side of the blockmake an angle of 60 degrees with thecylinders in the right side of the block. Themain bearing caps are fastened to the blockwith four bolts per cap.

The cylinder liners can be removed forreplacement. The top surface of the block isthe seat for the cylinder liner flange. Enginecoolant flows around the liners to keep themcool. Three O–ring seals around the bottom ofthe liner make a seal between the liner andthe cylinder block. A filler band goes underthe liner flange and makes a seal between thetop of the liner and the cylinder block.

The engine has a separate cylinder head foreach cylinder. Four valves (two intake and twoexhaust), controlled by a push rod valvesystem, are used for each cylinder. Valveguides without shoulders are pressed into thecylinder heads. The opening for the sparkplug is located between the four valves.

There is an aluminum spacer plate betweeneach cylinder head and the block. Coolantgoes out of the block through the spacer plateand into the head through eight openings ineach cylinder head face. Grommets the widthof the spacer plate prevent coolant leakage.Gaskets seal the oil drain passages betweenthe head, spacer plate and block.

Figure 44. Left Side Of 3516 Engine(1) Covers for camshaft and valve lifter inspection. (2) Covers for crankshaft main and rod bearinginspection.

Covers (1) (Figures 45) allow access to thecamshafts and valve lifters.

Covers (2) allow access to the crankshaftconnecting rods, main bearings and pistoncooling jets. With covers removed, all theopenings can be used for inspection andservice.

Pistons, Rings And ConnectingRodsThe aluminum pistons have an iron band forthe top two rings. This helps reduce wear onthe compression ring grooves. The pistonshave three rings; two compression rings andone oil ring. All the rings are located above thepiston pin bore. The oil ring is a standard(conventional) type. Oil returns to thecrankcase through holes in the oil ringgroove. The top two compression rings arealso the standard (conventional) type.

The connecting rod has a taper on the pinbore end. This gives the rod and piston morestrength in the areas with the most load. Fourbolts set at a small angle hold the rod cap tothe rod. This design keeps the rod width andweight to a minimum, so that the largestpossible rod bearing (and crank journal) canbe used and the rod can still be removedthrough the top of the liner bore.

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CrankshaftThe crankshaft changes the combustionforces in the cylinder into usable rotatingtorque which powers the engine. A vibrationdamper of the fluid type is used at the front ofthe crankshaft to reduce torsional vibrations(twist on the crankshaft) that can causedamage to the engine.

The crankshaft drives a group of gears on thefront and rear of the engine. The gear groupon the front of the engine drives the oil pump,water pump, fuel transfer pump, governor orgovernor actuator and two accessory drives.The gear group on the rear of the enginedrives the camshafts.

Lip seals and wear sleeves are used at bothends of the crankshaft for easy replacementand a reduction of maintenance cost. Pressureoil is supplied to all main bearings throughdrilled holes in the webs of the cylinder block.The oil then flows through drilled holes in thecrankshaft to provide oil to the connecting rodbearings. The crankshaft is held in place byfive main bearings on the G3508, seven mainbearings on the G3512, and nine mainbearings on the G3516. A thrust plate at eitherside of the center main bearing controls theend play of the crankshaft.

CamshaftsThe G3512 and G3516 have two camshafts perside that are doweled and bolted together tomake a camshaft group. Each G3516 camshaftgroup is supported by nine bearings and isdriven by the gears at the rear of the engine.Each G3512 camshaft group is supported byseven bearings and is driven by the gears atthe rear of the engine. The G3508 has onecamshaft per side. Each camshaft is supportedby five bearings and is driven by the gears atthe rear of the engine.

As the camshaft turns, each lobe moves a lifterassembly. There are two lifter assemblies foreach cylinder. Each lifter assembly moves apush rod and two valves (either intake orexhaust). The camshafts must be in time withthe crankshaft. The relation of the cam lobes

to the crankshaft position cause the valves ineach cylinder to operate at the correct time.

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Electrical System

Engine Electrical SystemThe electrical system has three separatecircuits: the charging circuit, the startingcircuit and the low amperage circuit. Some ofthe electrical system components are used inmore than one circuit. The battery (batteries),circuit breaker, ammeter, cables and wiresfrom the battery are all common in each of thecircuits.The charging circuit is in operation when theengine is running. An alternator makeselectricity for the charging circuit. A voltageregulator in the circuit controls the electricaloutput to keep the battery at full charge.

The starting circuit is in operation only whenthe start switch is activated.

The low amperage circuit and the chargingcircuit are both connected to the same side ofthe ammeter. The starting circuit connects tothe opposite side of the ammeter.

Charging System Components

NOTICENever operate an alternator without a batteryin the circuit. Making or breaking analternator connection with heavy load on thecircuit can cause damage to the voltageregulator.

Alternator (3T6352 & 4N3986)

Figure 45. Alternator(1) Regulator. (2) Roller bearing. (3) Stator winding. (4) Ball bearing. (5) Rectifier bridge. (6) Field winding.(7) Rotor assembly. (8) Fan.

The alternator (Figure 45) is driven by beltsfrom the crankshaft pulley. This alternator is athree phase, self-rectifying charging unit, andthe regulator (1) is part of the alternator.

This alternator design has no need for sliprings or brushes, and the only part that hasmovement is the rotor assembly (7). Allconductors that carry current are stationary.The conductors are: the field winding (6),stator windings (3), six rectifying diodes, andthe regulator circuit components.

The rotor assembly has many magnetic poleslike fingers with air space between eachopposite pole. The poles have residualmagnetism (like permanent magnets) thatproduce a small amount of magnet-like lines offorce (magnetic field) between the poles. Asthe rotor assembly begins to turn between thefield winding and the stator windings, a smallamount of alternating current (AC) isproduced in the stator windings from thesmall magnetic lines of force made by theresidual magnetism of the poles. This ACcurrent is changed to direct current (DC)when it passes through the diodes of therectifier bridge (5). Most of this current goesto charge the battery and to supply the lowamperage circuit, and the remainder is sent onto the field windings. The DC current flowthrough the field windings (wires around an

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iron core) now increases the strength of themagnetic lines of force. These stronger linesof force now increase the amount of ACcurrent produced in the stator windings. Theincreased speed of the rotor assembly alsoincreases the current and voltage output ofthe alternator.

The voltage regulator is a solid state(transistor, stationary parts) electronic switch.It feels the voltage in the system, and switcheson and off many times a second to control thefield current (DC current to the fieldwindings) to the alternator. The output voltagefrom the alternator will now supply the needsof the battery and the other components in theelectrical system. No adjustment can be madeto change the rate of charge on thesealternator regulators.

Grounding PracticesProper grounding for vehicle and engineelectrical systems is necessary for propervehicle performance and reliability. Impropergrounding will result in uncontrolled andunreliable electrical circuit paths which canresult in damage to main bearings andcrankshaft journal surfaces. Uncontrolledelectrical circuit paths can also cause electricalnoise which may degrade vehicle and radioperformance.

To insure proper functioning of the vehicleand engine electrical systems, and engine-to-frame ground strap with a direct path to thebattery must be use. This may be provided byway of a starting motor, a frame to startingmotor ground, or a direct frame to engineground.

Ground wires/straps should be combined atground studs dedicated for ground use only.The engine alternator must be battery (–)grounded with a wire size adequate to handlefull alternator charging current.

NOTICEThis engine may be equipped with a 24 voltstarting system. Use only equal voltage forboost starting. The use of a welder or highervoltage will damage the electrical system.

Starting Systems

There are two types of starting systemsavailable for Caterpillar Engines — air andelectric.

The choice of systems depends on availablilityof the energy source. Availablity of space forenergy of storage and ease of recharging theenergy banks are considerations fordetermining the type of starting system to beused.

ElectricElectric starting (Figure 46) is the mostconvenient to use. It is least expensive and ismost adaptable for remote control andautomation.

BatteriesBatteries provide sufficient power to crankengines long and fast enough to start. Lead-acid types are common, have high outputcapabiliites, and lowest first cost. Nickel-cadmium batteries are costly, but have longshelf life and require minimum maintenance.Nickel-cadmium types are designed for longlife and may incorporate thick plates whichdecrease high discharge capability. Consultthe battery supplier for specificrecommendations.

Two considerations in selecting properbattery capacity are:

• The lowest temperature at which the enginemight be cranked.

• The parasitic load imposed on the engine. Agood rule of thumb is to select a batterypackage which will provide at least four 30second cranking periods (total of 2 minutescranking). An engine should not be crankedcontinuously for more than 30 seconds orstarter motors may overheat.

Ambient temperatures drastically affectbattery performance and chargingefficiencies. Maintain 32°C (90°F) maximumtemperature to assure rated output. Impact ofcolder temperatures is described in Figure 47. 37

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Figure 46. Electric starting system.

Figure 47. Impact of Cold Temperatures.

Locate cranking batteries for easy visualinspection and maintence. They must be awayfrom flame or spark sources and isolated fromvibration. Mount level on nonconductingmaterial and protect from splash and dirt. Useshort slack cable lengths and minimizevoltage drops by positioning batteries near thestarting motor.

Disconnect the battery charger whenremoving or connecting battery leads. Solid-state equipment, i.e., electronic governor,speed switches, can be harmed if subjected tocharger’s full output.

Battery ChargerVarious chargers are available to replenish abattery. Trickle chargers are designed forcontinuous service on unloaded batteries.They automatically shut down to milliamperecurrent when batteries are fully charged.

Overcharging shortens battery life and isrecognized by excessive water loss.Conventional lead-acid batteries require lessthan 2 oz. (59.2 mL) make-up water during 30hours of operation.

Float-equalize chargers are more expensivethan trickle chargers are used in applicationsdemanding maximum battery life. These

chargers include line and load regulation, andcurrent limiting devices, which permitcontinuous loads at rated output.

Both trickle chargers and float equalizechargers require a source of A/C power whilethe engine is not running. Chargers must becapable of limiting peak currents duringcranking cycles or have a relay to disconnectduring cranking cycles. Where engine-drivenalternators and battery chargers are bothused, the disconnect relay usually disconnectsthe battery charger during engine crankingand running.

Engine-driven generators or alternators canbe used, but have the disadvantage ofcharging batteries only while the engine runs.Where generator sets are subject to manystarts, insufficent battery capacity couldthreaten dependability.

SolenoidA solenoid (Figure 48) is a magnetic switchthat does two basic operations:

a. Closes the high current starter motorcircuit with a low current start switchcircuit.

b. Engages the starter motor pinion with thering gear.

Figure 48. Solenoid Schematic.(1) Electromagnet. (2) Hollow cylinder. (3) Plunger. (4) Shift lever.

The solenoid switch is made of anelectromagnet (one or two sets ofwindings)(1) around a hollow cylinder(2).There is a plunger (core)(3) with a spring loadinside the cylinder that can move forward and

°F °C

Temperature vs. Output

27°C (80°F)Ampere Hours Output Rating

80

32

0

28

0

-18

100

65

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backward. When the start switch is closed andelectricity is sent through the windings, amagnetic field is made that pulls the plungerforward in the cylinder. This moves the shiftlever(4) (connected to the rear of the plunger)to engage the starter pinion drive gear withthe ring gear. The front end of the plungerthen makes contact across the battery andmotor terminals of the solenoid, and thestarter motor begins to turn the flywheel ofthe engine.

When the start switch is opened, current nolonger flows through the windings. The springnow pushes the plunger back to the originalposition, and, at the same time, moves thepinion gear away from the flywheel.

When two sets of windings in the solenoid areused, they are called the hold-in winding andthe pull-in winding. Both have the samenumber of turns around the cylinder, but thepull-in winding uses a larger diameter wire toproduce a greater magnetic field. When thestart switch is closed, part of the current flowsfrom the battery through the hold-in windings,and the rest flows through the pull-in windingsto motor terminal, then through the motor toground. When the solenoid is fully activated(connection across battery and motor terminalis complete), current is shut off through thepull-in windings. Now only the smaller hold-inwindings are in operation for the extendedperiod of time it takes to start the engine. Thesolenoid will now take less current from thebattery, and heat made by the solenoid will bekept at an acceptable level.

Starter Motor

Figure 49. Starter Motor Cross Section(1) Field. (2) Solenoid. (3) Clutch. (4) Pinion. (5) Commutator. (6) Brush assembly. (7) Armature.

The starter motor (Figure 49) is used to turnthe engine flywheel fast enough to get theengine running.

The starter motor has a solenoid(2). When thestart switch is activated, the solenoid willmove the starter pinion(4) to engage it withthe ring gear on the flywheel of the engine.The starter pinion will engage with the ringgear before the electric contacts in thesolenoid close the circuit between the batteryand the starter motor. When the circuitbetween the battery and the starter motor iscomplete, the pinion will turn the engineflywheel. A clutch (3) gives protection for thestarter motor so that the engine cannot turnthe starter motor too fast. When the startswitch is released, the starter pinion will moveaway from the ring gear.

Circuit BreakerThe circuit breaker (Figure 50) is a switchthat opens the battery circuit (5) if the currentin the electrical system goes higher than therating of the circuit breaker.

A heat activated metal disc (4) with a contactpoint (3) completes the electric circuitthrough the circuit breaker. If the current inthe electrical system gets too high, it causesthe metal disc to get hot. This heat causes adistortion of metal disc which opens thecontacts (2)and breaks the circuit. A circuitbreaker that is open can be reset after it cools.Push the reset button (1) to close the contactsand reset the circuit breaker.

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NOTICEFind and correct the problem that causes thecircuit breaker to open. This will help preventdamage to the circuit components from toomuch current.

Figure 50. Circuit Breaker Cross Section(1) Reset button. (2) Disc in open position. (3) Contacts.(4) Disc. (5) Battery circuit terminals.

Figure 51. Magnetic Pickup(1) Clearance dimension. (2) Pole piece. (3) Wire Coils.(4) Locknut. (5) Gear tooth. (6) Housing.

Magnetic PickupThe magnetic pickup (Figure 51) is a singlepole, permanent magnet generator made ofwire coils (2) around a permanent magnetpole piece (4). As the teeth of the flywheelring gear (5) cut through the magnetic lines offorce around the pickup, an AC voltage isgenerated. The frequency of this voltage isdirectly proportional to engine speed.

Magnetic SwitchA magnetic switch (relay) is used for thestarter solenoid circuit. Its operationelectrically, is the same as the solenoid. Itsfunction is to reduce the low current load onthe start switch and control low current to thestarting motor solenoid.

Water Temperature Connector Switch

Figure 52. Water Temperature Contactor Switch

The contactor switch for water temperature(Figure 52) is installed in the regulatorhousing. No adjustment to the temperaturerange of the contactor can be made. Theelement feels the temperature of the coolantand then operates the micro switch in thecontactor when the coolant temperature is toohigh. The element must be in contact with thecoolant to operate correctly. If the reason forthe engine being too hot is caused by lowcoolant level or no coolant, the contactorswitch will not operate.

The contactor switch is normally connected tothe electric shutoff system to stop the engine.The switch can also be connected to an alarmsystem. When the temperature of the coolantlowers again to the operating range, thecontactor switch opens automatically.

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Air Inlet Temperature Switch

Figure 53. Air Inlet Temperature Switch.

The contactor switch for air inlet temperature(Figure 53) is installed in the inlet airmanifold. No adjustment to the temperaturerange of the contactor can be made. Theelement feels the temperature of the inlet airand then operates the micro switch in thecontactor when the inlet air temperature is toohigh. The element must be in contact with theinlet air to operate correctly.

The contactor switch is normally connected tothe electric shutoff system to stop the engine.The switch can also be connected to an alarmsystem. When the temperature of the inlet airlowers again to the operating range, thecontactor switch opens automatically.

Air StartThe air starting motor (Figures 54-56) is usedto turn the engine flywheel fast enough to getthe engine running.

Figure 54. Typical Air Starting System(1) Air starting motor. (2) Relay valve. (3) Oiler.

The air starting motor (1) can be mounted oneither side of the engine. Air is normallycontained in a storage tank and the volume ofthe tank will determine the length of time theengine flywheel can be turned. The storagetank must hold this volume of air at 1720 kPa(250 psi) when filled.

For engines which do not have heavy loadswhen starting, the regulator setting isapproximately 690 kPa (100 psi). This settinggives a good relationship between crankingspeeds fast enough for easy starting and thelength of time the air starting motor can turnthe engine flywheel before the air supply isgone.

If the engine has a heavy load which can notbe disconnected during starting, the setting ofthe air pressure regulating valve needs to behigher in order to get high enough speed foreasy starting.

The air consumption is directly related tospeed; the air pressure is related to the effortnecessary to turn the engine flywheel. Thesetting of the air pressure regulator can be upto 1030 kPa (150 psi) if necessary to get thecorrect cranking speed for a heavily loadedengine. With the correct setting, the airstarting motor can turn the heavily loadedengine as fast and as long as it can turn alightly loaded engine.

Other air supplies can be used if they have thecorrect pressure and volume. For good life ofthe air starting motor, the supply should befree of dirt and water. A lubricator with SAE 10non detergent oil [for temperatures above 0°C(32°F)], or air tool oil, #1 diesel fuel orequivalent [for temperatures below 0°C(32°F)] should be used with the startingsystem. The maximum pressure for use in theair starting motor is 1030 kPa (150 psi).

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Figure 55. Typical Air Start Installation(4) Air start control valve.

Figure 56. Air Starting Motor(5) Air inlet. (6) Vanes. (7) Rotor. (8) Pinion. (9) Gears.(10) Piston. (11) Piston spring.

The air from the supply goes to relay valve(2). The start control valve (4)(Figure 56) isconnected to the line before the relay valve.The flow of air is stopped by the relay valveuntil the start control valve is activated. Theair from the start control valve goes to piston(10) behind pinion (8) for the starting motor.The air pressure on the piston puts spring (11)in compression and puts the pinion inengagement with the flywheel gear. When thepinion is in engagement, air can go outthrough another line to the relay valve. The airactivates relay valve which opens the supplyline to the air starting motor.

The flow of air goes through the oilerr (3)where it picks up lubrication for the airstarting motor.

The air with lubrication goes into the airmotor through air inlet (5). The pressure ofthe air pushes against vanes (6) in rotor (7),

and then exhausts through the outlet. Thisturns the rotor which is connected by gears(9) and a drive shaft to the starting motorpinion(8) which turns the engine flywheel.

When the engine starts running, the flywheelwill start to turn faster than the starting motorpinion. The pinion retracts under thiscondition. This prevents damage to the motor,pinion or flywheel gear.

When the start control valve is released, theair pressure and flow to the piston behind thestarting motor pinion is stopped, the pistonspring retracts the pinion. The relay valvestops the flow of air to the air starting motor.

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Engine Monitoring andShutdown Protection

G3500 Engines can be configured to use oneof three systems to monitor engineparameters and provide engine shutdownprotection: Junction Box (Energize ToShutdown), Junction Box (Energize To Run),and/or a Control Panel (Status Control). Fordetailed information on the operation,troubleshooting and engine control panel set-up, refer to SENR6420, Systems OperationTesting & Adjusting, Remote Control Panel(Status) For G3500 Engines (EIS).

Junction Box

Fgure 57. Junction Box (Shown With Door Open)(1) Terminal strips. (2) Gauges. (3) Emergency stopswitch.

The junction box (1) (Figure 57)provides acentral location to mount the various gauges,meters, indicators and switches available foruse on the engine. It also contains space forthe electrical terminal strips (2) that connect

the sensors, pick–ups and relays to the gauges(3). The junction box is also used to provideshutoff protection for the engine.

An Emergency Stop Push Button (ESPB) maybe located on the junction box panel. Whenthis button (3) is pressed, the fuel is shut offand the engine ignition is turned off (theground to the shutdown switch of theElectronic Ignition System control is opened).

To restart the engine, the ESPB must beturned until it pops out.

NOTICEThe Emergency Stop Push Button (ESPB) isnot to be used for normal engineshutdown. To avoid possible engine damage,use the Engine Control Switch (ECS) fornormal engine shutdown.

If the junction box is configured for anEnergized To Run (ETR) or an Energized ToShutoff (ETS) application, a gas shutoff valvewill be included in the engine installation. Inan Energize To Run set up, the gas shutoffvalve must remain energized to operate theengine. In the most common Energized ToShutoff system, the gas shutoff valve has amechanical (manual) latch that must be set. Ifa fault is detected, the gas shutoff valve will beenergized to unlatch the gas shutoff valve andstart a two stage shutoff sequence.

The junction box is used to monitor engine oilpressure, coolant temperature, starting motoroverspeed, and engine overspeed conditions.

Note: If the junction box monitors anoverspeed condition, or if the Emergency StopPush Button is activated, a relay will beenergized and cut ignition to the engine.

Note: If the junction box monitors a loss ofengine oil pressure, or detects a high coolanttemperature, a relay will shut the fuel off tothe engine.

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Figure 58. Engine Start/Stop Panel(1) Indicator lights. (2) Diagnostic reset plug. (3) Engine Control Switch(ECS). (4) Status control module. (5) Emergency Stop Push Button(ESPB).

Engine Start/Stop Panel

Engine Control SwitchThe Engine Control Switch (ECS)(3) of thecontrol panel has four positions – AUTO,MANUAL START, COOLDOWN/STOP,OFF/RESET. See Figure 58. If the ECS is inthe AUTO position and a signal to run isreceived from a remote initiate contact (IC), orthe ECS is placed in the MANUAL/STARTposition, the engine will crank, terminatecranking and run. Engines equipped withelectronic governors will run at low idle speeduntil lube oil pressure has exceeded the idlelow oil pressure set point, then the relaycontact of the governor control will close andthe engine will accelerate to rated speed.Engines with hydra-mechanical governors willaccelerate to their speed setting immediatelyafter crank termination. The engine will rununtil the Engine Control Switch (ECS) isturned to COOLDOWN/STOP, OFF/RESET, orthe remote initiate contact opens. Once theECS is moved to the COOLDOWN/STOPposition, or if in the AUTO position and theremote initiate contact opens, the engine willrun at a lower speed for a short period of time,if the cool down feature was selected using theDDT. If the cool down feature was notprogrammed the engine will shut downimmediately. The engine is then capable ofimmediate restart.

When the engine is to be shutdown, eithermanually (through the engine control switch)or automatically (through the engineprotection system), a two stage shutdownsequence will occur. First, a relay will de-energize the gas shutoff valve, and will shutthe fuel off to the engine. In the second step ofthe shutdown sequence the ground to theshutdown switch of the Electronic IgnitionSystem control is opened.

Emergency Stop Push ButtonAn Emergency Stop Push Button (ESPB)(5) islocated on the Engine Start/Stop Panel. Asecond Emergency Stop Push Button islocated on the engine itself (junction box),when a remote start/stop panel is used. Whenthis button is pressed, the fuel is shut off andthe engine ignition is turned off (the groundto the shutdown switch of the ElectronicIgnition System control is opened).

To restart the engine, the ESPB must beturned until it pops out.

NOTICEThe Emergency Stop Push Button (ESPB) isnot to be used for normal engineshutdown. To avoid possible engine damage,use the Engine Control Switch (ECS) fornormal engine shutdown.

Fuel Selector SwitchThe Fuel Selector Switch (optional) is a twoposition switch which provides input to theElectronic Ignition System Control Module.Two selections can be made with the switch.One position is for use with propane fuel only.The other position is for any other fuel used.Use of the PROPANE position signals the EISControl Module to increase the range oftiming retard because of the heat value ofpropane gas.

Status Control Module

Figure 59. Status Control Module (SCM)

The Engine Status Control Module (SCM)(Figure 59) is used to monitor engineparameters (oil pressure, coolant temperature,

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engine overspeed and over cranking of thestarter motor). It also provides an engineprotection system (two stage shutdown) andcontrols normal start/stop functions. When afault signal is detected, the display is also usedto indicate diagnostic codes, to aid introubleshooting.

The Status Control Module contains a relay,terminal strips and overspeed verify.

46

47

DC Control Panel for Gas Engine Chiller

48

DC Control Panel for Gas Engine Chiller (Inside View)

49

Abbreviations and Symbols

lekq7518 g3500 engine basics

Documents

digital diagnostic

gas inlet

naturally

counterclockwise

rocker arm

heavily loaded

low amperage

dc control