Well, before it lost pressure immediately after the pump shut off. After I replaced the regulator it seemed to hold, but because of your last post, I put a gauge on it and it's more or less 0 PSI after 10 minutes....

To NAPA again, methinks... Lemme know what you think

Thanks

 

The pump needs to be isolated from the plenum to diagnose a leaky check valve in the pump. You can do that by modifying the pressure tester to connect directly to the fuel line at the fuel filter. Then activate the pump, pressure should be ~75psi to ~108psi and must remain above 50psi for 10 minutes after the pump shuts off. If it leaks down below 50psi, the pump is faulty.

 

Ok. Will do that and post results.

Thanks

 

Ok, pump produces ~80 psi when activated. Pressure quickly leaks down to ~25 psi when pump shuts off.

Check valve in pump, I assume, is faulty.

1. Does this matter?
2. Could it contribute to the symptoms I'm having? (Not me personally, my truck lol)
3. If not, how can you test the manifold fuel system without replacing the pump?

Thanks

 

Either the check valve in the pump is faulty, or the flex line from the pump to the module is leaking. Also, the pressure is very close to the bare minimum which will affect fuel volume to the injector, it needs a new fuel pump module. These things are fussy about pumps, they really like AC Delco & Delphi... aftermarket stuff, not so much.

1. Yes; it will affect start up, mainly when the engine is cold. It may also have a fuel starvation problem under load.
2. Possibly, but there is most likely something else contributing to the problem also.
3. Very simple, you can't be sure all leaks are repaired until leakdown at the rail stays within spec, (remain above 50psi for 10 minutes after the pump shuts off). The fuel delivery system on this engine is kinda like Christmas tree lights... you need to fix problems as you find them, one at a time, until everything works

 

Ok. guess I 'm replacing a pump for christmas...


EDIT: What exactly do you mean by the fuel pump module, anyway? Never been inside one of these... a TBI pump is the only in tank I've ever replaced...

 

"Module" is common terminology for the entire tank unit. On your '95 "W" Vortec, it's very similar to the TBI pump set up. You can get the "sender" which includes the level sender and the "hanger", and sometimes the pump as well. The hanger is what the pump and level sender are mounted to in the tank. If your fuel gage is working OK, you could get by with just replacing the pump.

 

wow.... best damn thread on here about this problem so far! and best of all, its my exact symptoms, exact motor! sorry for your troubles as well, but boy am I glad I'm not the only one... my only downside is that I just put in a new pump 2 years ago... I guess i'll be buying a fuel pressure gauge to test my system now... glad its a lifetime pump, but they don't cover my aggrivation of dropping that tank LOL definately following this one all the way to the end, please don't stop posting about your work like everyone else does... seems you get all the way to a possible solution but they don't post back.

THANK YOU!

 

Ok.

And I'm glad this is helping someone else out... Hope you're having better luck than me lol...

 

I corrected my post regarding TPS passages.....I meant IAC passages in the throttle body.

I really should proof-read before hitting submit.