Hi,

On my 91 Z28 with an L98, I've got a problem where the fuel pressure drops rapidly after priming. With my fuel gauge connected, I can see that it goes down within seconds from 44 to 35 or so, then kind of trickle after that. This is without the engine running. The engine runs fine, and with the engine running the pressure is stable at 44.

If I clamp the rubber return hose, that would tell me that either the FPR is leaking or the fuel pump check valve. I'm suspecting the fuel pump check valve, but how would I determine if it's the fuel pressure regulator?

I don't suspect the injectors. The drop is too fast, and I'm not running rich, and idle is smooth.

Any suggestions?

 

Well mine does basically the same thing. Rock steady with engine running. But with engine off, pressure drops quickly like 8-15 psi, then will hold there.

I've noticed alot of people posting they have the same issue, so I haven't even messed with this lately. My car runs / idle very smooth as is, so to me it hasn't been a "problem" I Can find enough things I need to get done without creating more :P








HTH

 

The FPR won't cause a pressure loss after the
pump stops, it just meters the pressure
back to the tank..

90% of the time, it's the pump's checkvalve
at fault, the other 10% of the time
it's leaking injector(s)

Clamp the return line after pressuizing
like you
suggest, that will point at the pump or
the injs.

mike