Rennbay Injector Seal Kit





By Andre Ruest


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.


Image 1 - Removing the fuel pump fuse at #34

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.


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


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


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


Image 6 - Injector at cylinder #1


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

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



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

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.


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

0-280-150-730 18.45 193.9 139.5 43.5 3

Porsche v8-5.0l, v8-5.4l

Part Number  lbs/hr cc /min grams /min  PSI BARS
0-280-150-730  18.45 193.9  139.5 43.5 3.0


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.

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

Mike, the S4's and later need a larger lower o-ring, to seal the larger hole in the intake.
I am measuring the spare O-ring I have from my supplier, measures at 16.8mm OD and about 7.9mmID
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.
Bruce told me that they will fit without any changes except the 16mm o-rings. Bosch p/n 0280156013
seal kit:
For a GTS 1992: 928.110.904.00
For a 1985-1986 S2: 944.110.901.00
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).

You still need to change the lower o-ring to the larger size for the 87 and later cars.
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.
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.

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).
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)



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

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