CIS Lambda Fuel Pressure Regulator O ring

[Walt Fricke]

The CIS Lambda fuel distributor has a system fuel pressure regulator assembly which screws into the fuel distributor. The Porsche parts diagrams have an exploded diagram of this assembly, with a lock nut, a spring, some washers and spacer to set the pressure, and a housing and a moving cylinder, which you dare not drop. At the far or innermost end of this assembly is shown a small O ring. I don't know if it fits on the end of the assembly, or into a groove inside the FD, but it is there. And the catalogs only show all this as an assembly, with no separate part numbers or dimensions for any of the parts.

A mechanic friend tried a place he knows has these, but they wouldn't sell him any, or even tell him the dimensions. Bosch may hold this information close to its heart (or pocket book).

Does anyone know the dimensions of this small O ring?

Anyone know where to go to get one of this dimension in Viton?

Mechanics tell me these can go bad, and this one has been in use for a long time. One guy said they can cause frustrating intermittent running issues. Another said he had seen FDs where this O ring was absent entirely, presumably having broken apart and been recirculated to the fuel tank. I solved my running issues without disassembly and getting my borescope into this area to see what was what. And without a replacement in hand, was reluctant to trying to fish the old one out, lest that damage it. But I would like to have a couple of the O rings so I can replace the old one just in case.

[LM3929]

check under my name I added the sizes that I used on my FD and they are not leaked yet

LM3929

Lorne M

[boyt911sc]

Walt,

Post a picture of the FD primary valve you have including the FD number. Do you have an FD-077? PM me your shipping address and will send a couple o-rings.

Tony