http://www.rennbay.com/injectortutorial.htm

This write-up is based on installation of the kit in a 1986 Porsche 944 Turbo. The usual disclaimers apply as to individual cars that may vary. Please follow all safety precautions regarding working on the engine, fuel system and the engine compartment.

A number of preparatory steps are necessary to install the kit. To gain proper access to the injectors it is not absolutely necessary to disconnect the fuel lines from the fuel rail. However, I found it much easier to work with the lines disconnected from the rail. This way it was easy to take the rail away from the car and remove the injectors from the rail.

• Removing the fuel rail
  • It will be necessary to disconnect the fuel lines before removing the fuel rail
  • Depressurize the fuel system. There are 3 possible ways of doing this
    • Let the car sit for a few days until the fuel system depressurizes.
    • Start the engine and remove the fuel pump fuse at #34 on the fuse and relay board (see Image 1). The engine will stop from lack of fuel in a few seconds.
    • Remove the fuel pump fuse at #34 on the fuse and relay board (see Image 1) and then attempt to start the engine. The engine may or may not start.
    • Disconnect the negative lead from the battery.

Image 1 - Removing the fuel pump fuse at #34

• Next, stuff some rags under the fuel pressure regulator and the fuel damper to catch any remaining fuel in the lines. Then, unscrew the hose clamp at the fuel pressure regulator (#1 in Image 2) which holds the fuel return line and pull off the fuel return line. Next, unscrew the fuel line from the fuel pump using a 24 mm wrench on the fuel damper body nut and a 19 mm wrench on the fuel line nut. (#2 in Image 2). Be prepared to use some force as this nut is very tight to prevent fuel leakage. If your car is equipped with cruise control, you must also remove the cruise control line from the intake manifold (#3 in Image 2) and the control unit (#4 in Image 2). Pull the vacuum lines from both the damper and pressure regulator (#5 and #6 in Image 2).

Image 2 - Fuel rail and fuel lines. 1. Fuel return line. 2. Fuel line nut. 3. Cruise control line hold-down bolt. 4. Cruise control servo unit. 5. Vacuum line to fuel damper. 6. Vacuum line to fuel pressure regulator.

• Then attach the fuel lines out of the way (See Image 3) and remove the fuel rail plastic covering. It is held in place with three plastic connectors (#1 in Image 3).

Image 3 - Fuel lines removed and attached out of the way and fuel rail cover

• Using a small flat tip screwdriver, disengage the wire clips on the fuel injector electrical connectors plugs and disconnect the plugs. Move the fuel injector wiring harness out of the way (Image 4).

Image 4 - Unclipped connector for fuel injector. Notice the metal retaining wire around the connector ( #1 in Image).

• The fuel rail is held by four (4) 10 mm bolts. Two are bolted to the cam cover (the forward bolt can be seen in #2 of Image 4), and two are bolted to the intake manifold itself. Using a 10 mm socket and an extension unbolt the 4 bolts (see Image 5). Unclip the spark plug wires from the rail and pull them from the spark plugs. You can then pull out the fuel rail. Be careful not to break the fuel injector plastic tips as you are pulling. Have rags ready to collect escaping fuel from the rail. Drain as much fuel as possible from the rail and store away from heat and sparks.

Image 5 - Unbolting the forward fuel rail to intake manifold bolt.

• Next, to remove the individual injectors from the rail you must take off the metal retaining clip at the fuel rail (see Image 6) and pull out the injector.

Image 6 - Injector at cylinder #1

• Image 7 shows the injector plastic end cap. Notice how the rim is cracked and the accumulated debris on the tip.

Image 7 - Injector tip. Notice the debris and the broken rim on the end cap.

• The next step is to remove the plastic injector cap the injection end rubber seal, the injection end plastic ring, and the rail end rubber seal. The easiest way to remove the plastic end cap is to slice it open with needle nose pliers pulling from the rim. Once the end cap is off the rubber seal and plastic ring are easy to pull. Clean the outside with injector cleaner liquid.

Image 8 - Bottom injector with seals, end cap and plastic ring removed

• Image 9 shows the Rennbay injector seal kit at the top and the old seals at the bottom. Each kit contains 2 rubber seals, one plastic ring, and one plastic end cap for resealing one injector.

Image 9 - Rennbay injector seal kit for one injector at the top compared to the old seals at the bottom.

• After cleaning the outside, you may want to spray some injector cleaner inside or have your injectors professionally cleaned.
• Next, put the seals on. Begin by placing the injection end plastic ring followed by the rubber seal. Next look at the injection end (see Image 10 and 12). You will notice a groove circling the end. You have to snap the plastic end cap on such that it will completely cover the groove. Insert the cap making sure that the needle is lined up with the hole at the top of the cap. You will feel a first "click" as the end cap engages the top portion of the groove. Then press the end cap against a piece of wood to achieve the second final "click" as the cap engages and passes the bottom portion of the groove. Finally, put on the rail end rubber seal. Image 11 shows two injectors. The top still has the old seals and plastic end cap, while the bottom one has the new seals and end cap on.

Image 10 - Injection end. Notice the small needle protruding out and the groove circling the metal.

Image 11 - Two injectors. Top still has the old seals, Bottom has the new seals

Image 12 - Notice the injector needle at the center of the hole on the end cap.

• Reinstall everything making sure that you have a proper seal everywhere. Once the fuel rail and the fuel lines are all nice and tight, you should test fuel flow before you turn on the engine. First, reconnect the battery negative. Then insert the fuel pump fuse at #34 which you removed to depressurize the system. Next, remove the DME relay and jumper terminals 30 and 87b (see Image 13). This will activate your fuel pump and feed fuel to the injectors. As the fuel flows to the injectors inspect all connections for leaks. If there are any leaks, remove the jumper and tighten the appropriate connections until there are no more leaks. Put back the DME relay, start the car and again inspect for leaks.

Image 13 – Socket for the DME relay.

Different offers of seals for the Bosch :

This is a confirmed 1993 version

1992 GTS injector
0 280 150 730 Injection Valve
928 606 119 02

Injector Body
Part Number Lower O-Ring Seal/Insulator Upper O-Ring Spacer Washer Filter Basket Protective Cap
0 280 150 730 1 280 210 765 --- 1 280 210 752 1 280 113 710 1 287 430 752 1 280 423 731

BOSCH LBS/HR CC/MIN GRAMS PSI BAR
0-280-150-730 18.45 193.9 139.5 43.5 3

Porsche v8-5.0l, v8-5.4l

Porsche injector seal kit 928 110 904 00

ID 7.8 mm
OD 16.8 mm

7.78mm top injector dia; 7.8mm int dia of bottom seal.

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The top of the injector at that point has a minimum design tolerance of 7.7mm where the o-ring fits.

The Bosch o-ring size spec for the top is 7.52mm 0.18mm (and interestingly, for the design III aka EV6 body, which has the same dimension at that point as earlier EV1 injectors, Bosch changed the o-ring spec to 7.52 0.13mm - guaranteeing its slightly smaller than the injector body).

If the o-rings you're using can be rotated freely or have slack where they fit, they're too large. While they might seal ok, if they twist or are pinched slightly by the fuel rail where the injector seats, it could create a small gap. I now only buy Bosch o-rings for my injectors.

edit: Correct o-ring specs can be found in the Bosch schematics in this post here.

edit2: I just looked up the correct Bosch part numbers.. they are:

S4 top o-ring (and top/bottom both for S3): 1 280 210 752
S4 bottom o-ring: 1 280 210 765

Hilton
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Mike, the S4's and later need a larger lower o-ring, to seal the larger hole in the intake.
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I am measuring the spare O-ring I have from my supplier, measures at 16.8mm OD and about 7.9mmID
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My understanding from other posts here on Rennlist is that the early 32V motors use the stock Bosch o-rings that new injectors come with for both top and bottom.

I've got a bunch of those O-rings from Bosch kit 1-287-010-704 that roger supplied for my 86 car, and that fit the 944 too, but they look to be same diam. More to follow.
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Bruce told me that they will fit without any changes except the 16mm o-rings. Bosch p/n 0280156013
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seal kit:
For a GTS 1992: 928.110.904.00
For a 1985-1986 S2: 944.110.901.00
Theo
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As an update - it turns out the correct o-rings for the lower end of S4 injectors are 17mm, not 16mm.

After much hunting I dug up a handy Bosch fuel injector catalogue that lists the correct Bosch part numbers for injector o-rings, including the unusual one for the S4.

The correct Bosch part is actually 17mm OD, 4.6mm thickness, for the intake end of the injector on an S4. The correct lower o-ring is also a red viton one, like you get in the Porsche injector seal kit.

The Bosch part number corresponds to a box of 5 of the lower seals - so I've ordered 5 boxes, which gives me enough for 3 cars, plus one left over.

Once the o-rings arrive, and I've had a chance to measure and compare to the ones I've got from Roger, I'll post up the correct part numbers and some pictures (as well as the correct Bosch part numbers for the top o-ring, which is the same as the lower o-ring for 85/86).
Hilton
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You still need to change the lower o-ring to the larger size for the 87 and later cars.
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The o-ring in the picture is Viton (std 928) and the stock one on the injector is Buna-n

FWIW, I have been using buna-n large o-rings on the new injectors which have been working great.
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I am interested in why you moved to the older spec Nitrile (Buna-n) for the injector O rings?
Viton seems to have much better properties for the application and is the preferred choice for Injector O rings.
Roger

__________________
Firstly, o-ring part numbers. These are the correct Bosch part numbers as specified for the 928 injectors:

S4 top o-ring (and top/bottom both for S3): 1 280 210 752
S4 bottom o-ring: 1 280 210 765

John Speake was able to source the S4 bottom ones for me - as they're unusual. The others are commonly available. Or you S4 owners can just get the Porsche part 928 110 904 00 for the o-rings (its an injector gasket kit for the stock S4 injectors - one kit per injector).
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So specs summarized and avoiding confusion here...:
Upper O-ring: 944.110.901.00 Bosch: 1 280 210 752, OD:14,58mm, Thick:3,53mm ID: 7,52mm (std Bosch, fits 944 and 928 until 1987)
Lower O-ring: 928.110.904.00 Bosch: 1 280 210 765, OD:17,00mm, Thick:4,6mm ID: 7,8mm (fits 928S4, GT, GTS)

You can also choose a repair kit: 0 287 010 708 for 1987-1995 models, Porsche 928 110 904 00 (upper, lower, cap and ring)
You can also choose a repair kit: 0 287 010 704 for 1985-1986 models, Porsche 944.110.901.00 (upper, lower, cap and ring)

Theo
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Hallo,
ik zoek een Bosch onderdeel: 1 280 210 765. Dit zijn O-ringen voor injectoren. Ik zoek er 8, eventueel nog wat meer. Kunt u ze leveren en wat kosten ze?
Alvast bedankt,
Theo Jenniskens
http://www.jenniskens.eu

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Beste heer Jenniskens,

De o-ringen tbv de injectoren met onderdeelnr. 1280210765 kunnen we leveren.
Levertijd van de o-ringen is 1 a 2 dagen.
De o-ringen kosten per stuk, 6,52 euro incl.btw.

Hopende u hiermee voldoende te hebben geinformeerd.
Met vriendelijke groet,
Dennis Muris

Bosch Car Service Venlo
Rudolf Dieselweg 26
5928 RA Venlo
Tel: 077-3241108
info@boschcarservicevenlo.nl
www.boschcarservicevenlo.nl