FPRs and FPDs

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18 Mar 2013 10:01 #13915 by Kiln_Red
FPRs and FPDs was created by Kiln_Red
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.

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18 Mar 2013 22:19 #13923 by pcar928fan
Replied by pcar928fan on topic FPRs and FPDs
Good to know Austin! Thanks for sharing!

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

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21 Mar 2013 20:51 #13970 by mm928
Replied by mm928 on topic FPRs and FPDs
Yes - good tip!

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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23 Mar 2013 00:19 #13980 by 928mac
Replied by 928mac on topic FPRs and FPDs
I removed my dampeners and only use this adjustable regulator

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