SERVICE BULLETIN - Stanadyne Bulletin/523.pdfNozzle Body Lower Valve Guide Needle Valve Single “Low” Spring Nozzle Holder Body Assembly Rate Shaping Nozzle Assembly Nozzle Retaining

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.