gazfish

A couple of weeks a go I replaced my fuel tank cradle, fuel pump, check valve, and some hard lines and ever since it’s taken a lot more cranking to start.
Fitted a fuel pressure gauge a sure enough the pressure drops to zero after the pump stops, suspecting the last thing I touched I put the old check valve back on, even though the new one seemed to be fine when I tried to blow through it.
This made no difference but traced the issue to one of the FPR’s which are only a couple of years old.
Out of the car it held vacuum but I could blow air through from the feed to the return side. Worked it a bit with the MittyVac and it seemed to start behaving.
Back on the car and it’s now holding pressure.

The car sat for about a week with no fuel pressure, is it possible the diaphram just got stuck? Anyone else had this?

Bulvot

I had a fuel pressure damper with not too many miles on it that seemed to work ok with vacuum, but started to fail under pressure (being applied by a new turbo). Then, it eventually started to leak under vacuum as well. So, in my limited experience, they can start exhibiting failure symptoms in different scenarios then normal, and even seem to work ok in other scenarios. Once it starts to fail in one scenario, you can expect it to eventually fail in all scenarios. My recommendation, for what it's worth, would be to replace it.

gazfish

Thanks, if they were cheap I would just replace but they've joined the list of NLA and prices are 3x what I paid two years ago.
I'd consider fitting a knockoff copy if 2 years is the lifespan of a Bosch part.

dr bob

I'll speculate that you disturbed something in the system as you were replacing things in the back. a bit of crud found it's way to the FPR where it lodged and propped the regulator open slightly. That's all it takes. Good that you were able to get it cleared out, good also that it didn't end up in an injector. Or maybe some did... Keep an eye on plugs for a bit to see if any cylinders are suffering from low fuel flow.

Bulvot

Ah, I didn't realize that the '86 FPR's were no longer available. That does complicate things

Maybe run with it as it is and retest it on a somewhat frequent basis until the leak either recurs and you know that it must be replaced, or it doesn't recur and you're comfortable trusting it for the long term?

gazfish

Good point, I had the pump relay bypassed while checking for leaks before I ran the engine so hopefully that's reduced the chance of the injectors being impacted but will check plugs.Thanks