FPRs and FPDs

I came across an unusual failure of a Bosch fuel pressure regulator on a 928 this weekend. The car was running way rich, so I searched out all electrical possibilities first. Everything checked out fine, including the grounds. This left me scratching my head until I recalled this same car had previously taken longer than usual to start after a cool down. I also recalled hearing fuel being returned to the tank at a faster than usual rate. This left me curious as to the condition of the regulator and dampners. I pulled off the regulator and sucked on the vac port as hard as I could. Sure enough, the diaphragm wouldn't move. I put the regulator into a vise and inserted a screw driver through fuel return port. It took extreme pressure to move the diaphragm. Clearly, the diaphragm had migrated from where it was positioned the last time I had driven the car as I believe it was stuck open which was probably resulting in a lean condition at all but idle. This time it was very obviously stuck closed.

I reinstalled a known good regulator and the car was immediately restored to proper working order. We have all heard of regulators that fail by way of ruptured diaphragms, but I don't see many reports of this type of failure where the diaphragm simply becomes stuck. Just figured I'd pass this along. I know I will be including new FPDs and a new FPR on my next parts order.

Good to know Austin! Thanks for sharing!

Yes - good tip!

I removed my dampeners and only use this adjustable regulator