service bulletin - stanadyne bulletin/523.pdfnozzle body lower valve guide needle valve single...
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Stanadyne Corporation 92 Deerfield Road, Windsor, CT 06095, U.S.A. Tel: (860) 525-0821; Fax: (860) 683-4581; www.stanadyne.com
NO: 523R1 DATE: March 18, 2009
SERVICE BULLETIN
SUPERSEDES: S.B. 523 dated April 30, 1998
The Stanadyne rate shaping nozzle offers a simple, compact method of controlling
fuel flow rates during the early stages of the injection cycle. By throttling the fuel
flow before the needle valve reaches maximum lift, the RSN feature can help reduce
exhaust emissions, lower engine idle noise, and improve fuel economy. In addition,
the RSN design uses a single spring, eliminating the need for costlier two spring
injectors. A cutaway view of a typical 17/21mm injector with a rate shaping nozzle is
shown below in Figure 1.
The principles of RSN operation can be understood by studying Figures 2 and 3.
With the needle valve fully seated (Figure 2a), fuel pressure increases until spring
pressure is overcome and the valve lifts from its seat. As the valve lifts, the flow
rate is controlled through the cross sectional orifice (an annulus created between
SUBJECT: RATE SHAPING NOZZLE (RSN®) FEATURE FOR 17MM,
17/21MM AND 21MM INJECTORS
CUSTOMERS AFFECTED: DEUTZ, HATZ, IVECO, LOMBARDINI,
RUGGERINI, VM MOTORI, VOLKSWAGEN, YTO
Figure 1
Spray Orifice
Rate Shaping/Cross Sectional Orifice Area
Nozzle Body
Lower Valve Guide
Needle Valve
Single “Low” Spring
Nozzle Holder Body Assembly
Rate Shaping Nozzle Assembly
Nozzle Retaining Nut (17/21mm)
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the outside diameter of the needle valve and the inside diameter of the nozzle
body, as shown in Figures 1, and 2b). With the valve at its maximum lift, the cross
sectional orifice is wide open and full fuel flow through the spray orifices is
achieved (Figure 2c).
Injector Assembly Service
Servicing an injector assembly equipped with a rate shaping nozzle consists of
cleaning, component replacement, setting, and testing according to the procedures
outlined herein, the individual service specification, and the 99118 Conventional
∗ VCO Sac type shown for illustration purposes only. Other nozzle sac types are also used with the RSN feature.
No Fuel Flow Rate Shaping Full Fuel Flow
Figure 2a Figure 2b Figure 2c
Valve Covers Orifice (VCO) Sac Type*
Valve Closed Valve
Throttled
Cross Sectional Orifice (Annulus)
Maximum Valve Lift
Valve Open
Rate Shaping Area (Figure 2b)
Needle Valve Lift
Maximum Flow Area (Figure 2c)
Figure 3
Flow Rate
Maximum Valve Lift
Valve Closed (Figure 2a)
Rate Shaping Nozzle
Standard Nozzle
Injector Service Manual. The injector clamping fixture from kit P/N 29617
(Reference 99118 & 99920), fitted with the appropriate injector adapter plate
should be used when disassembling and re-assembling injectors to avoid damaging
the dowel pins (Figure 4).
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Figure 4
Injector Adapter Plate
Injector Clamping Fixture
(From Injector Service Kit, P/N 29167)
Spring Seat
Pressure Adjusting Shim
Pressure Adjusting Spring
Nozzle Holder Body Assembly
Dowel Pins
Adapter Plate Assembly Rate Shaping Nozzle
Assembly
Nozzle Retaining Nut
Nozzle Assembly Service
Nozzle assemblies with the rate shaping feature can only be cleaned or replaced as
a complete assembly.
IMPORTANT: Because the injector flow characteristics are dependent on
extremely close valve to body clearances and valve lift tolerances, grinding
or lapping of a rate shaping nozzle valve or nozzle body are not permitted.
The orifice holes and cleaning wires can be very small in diameter. Use a pin-vise
(P/N 16483) and exercise extreme care when cleaning nozzle assemblies to prevent
scoring or damage of the orifice holes. Never use a motorized and/or steel brush for
cleaning nozzle assemblies as orifice hole deformation may result.
Clean the nozzle needle valve with a felt pad. A clean, oiled and proper fitting
valve will slide to the bottom of the nozzle body under its own weight when
retracted 1/3 of its height and released.
Injector Assembly Testing
Injector assembly testing is performed using a standard hand-operated injector
tester to check nozzle opening pressure (NOP), spray pattern, and seat leakage.
Before testing, the injector assembly should be flushed using a “fast” handle stroke
(approximately 2 seconds of stroke duration). This will purge air from system and
seat the injectors internal components.
IMPORTANT: The traditional “nozzle chatter” (Ref. 99118) will either be
less pronounced or non-existent when testing injector assemblies equipped
with rate shaping nozzles. The lack of “chatter” is an acceptable
characteristic for the RSN design and should not be used as a basis to
determine injector/nozzle condition.
Nozzle Opening Pressure
1. The nozzle opening pressure is tested with a “slow” handle stroke
(approximately 6-10 seconds of stroke duration). Record the pressure at which
the nozzle valve opens and fluid flows through the nozzle spray orifices.
IMPORTANT: When performing NOP testing, injectors with RSN
nozzles may exhibit the following characteristics that are considered to
be normal:
• Nozzle “Hosing” or a non-atomized spray plume.
• Spray plume (flow) may not be present at all orifices.
• Nozzle chatter is minimal or non-existent.
2. If the opening pressure is incorrect, pressure adjusting shims (Ref. Figure 4)
may be added or subtracted to achieve the desired pressure. Typically,
each .025 mm (.001 inch) of shim represents approximately 3.8 bar (55 psi).
Whenever possible, a single shim is preferred but a maximum of two shims may
be used.
Valve Seat Tightness
1. Using a “slow” handle stroke (6-10 seconds), bring the pressure to the nozzle
opening pressure then allow pressure to drop at least 20.7 bar (300 psi) below
the actual opening pressure.
2. Dry the nozzle tip with a clean lint-free cloth and maintain the pressure for 5
seconds. Inspect the nozzle tip for wetness or leakage. Fluid drop formation is
not acceptable, but wetness on a used nozzle is permissible. Droplet formation
indicates the necessity for complete nozzle assembly replacement.
NOTE: Due to various fuel return configurations, some injectors may need to be
slightly inverted (nozzle end up) to ensure that return fuel does not flow down
onto the nozzle assembly during this test.
Fluid Leakage
External fluid leakage, other than from the fuel return port, is not acceptable and
must be repaired. Internal leakage can be checked as follows:
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1. Using a “slow” handle stroke (6-10 seconds), raise the pressure to 117.2 bar
(1700 psi). Release the handle and allow the pressure to fall.
2. Record the time it takes for the pressure to drop from 103.4 bar (1500 psi) to
69.0 bar (1000 psi). If the pressure decays in less than 10 seconds, the nozzle
assembly will require replacement.
Spray Pattern
1. Using a “fast” handle stroke (2 seconds), check for fuel flow (spray plume) from
each spray orifice hole. Poor plume atomization is acceptable, but non-existent
flow thru an orifice hole may indicate the need for nozzle assembly service or
replacement.
IMPORTANT: Poor spray plume atomization (hosing) may be evident
when checking spray pattern. This is considered normal for RSN
featured injectors and can be more pronounced on nozzle assemblies
that employ both the RSN feature and a VCO sac type.
Beginning of Injection (BOI) Sensor
This feature is no longer offered in current production. However, some engines
were originally fitted with one injector equipped with a proximity type sensor. The
sensor monitors the beginning of needle valve lift and supplies the Engine Control
Unit (ECU) with the necessary injection timing feedback for precise timing control.
The sensor can be tested for continuity: 95–115 ohms of resistance at room
temperature and 110–140 ohms resistance at engine operating temperature. The
sensor is non-serviceable except by complete nozzle holder body assembly
replacement. To avoid sensor damage during injector service, prevent metallic
debris from entering the spring chamber area of the nozzle holder body assembly
and never direct compressed air into the nozzle holder body assembly passages.
Warranty
Stanadyne warrants all RSN equipped injector assemblies and nozzles against
defects in material and workmanship in accordance with the Stanadyne Policies
and Procedures Manual (99966) as outlined in Section 4.0. Refer to the Stanadyne
service website for the latest warranty information.
Technical Support Group
Product Support Department
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Revision Date Changes
1 3/09 Remove specific injector/customer reference. Include additional
service information and procedures.