hello all
i have a 91 firebird with a 305 tbi...i just purchased this car and am slowly restoring it to its former glory..with that said i have a slight issue

when i got it i knew the fuel pump was bad ok no biggie i changed it it worked great and ran great had it running for about 15 mins and then shut it off...came back two days later to work on it and started it...nothing...have power going to pump but pump does not run...i have changed pump twice now due to this thinking it was just a faulty pump...but now im not sure...what could possibly kill my fuel pump after only 15 mins of running?? i have already checked the wiring for the entire fuel circuit and i have no breaks or anything any help is appreciated thanks alot

 

How much voltage do you have to the pump? You must test the harness as close to the pump as possible.

How much voltage do you have on the ground wire? You must test the harness as close to the pump as possible.

You say you have power to the pump. First Guess: Ground is bad.

 

I know how to check voltage to pump on the grey wire (12v) but how would i check the ground?

 

And what should the voltage be? I think the last time i checked it was reading 12.2vdc. Im guessing thats normal? What should it be when the engine is running? Still 12v or should it be whats coming off the alternator??

 

Connect voltmeter to ground wire near fuel pump. Try to run pump. More than one volt on that wire with the fuel pump running means the ground is insufficient. If the ground wire is broken somewhere, there'll be full voltage on that wire, as long as you're measuring between the pump and the break. Ground the wire, see if the pump runs.

The pump should get alternator voltage, but on my two Luminas there's about 1.5 volts less than alternator voltage due to the thin wires GM uses.

The pump ground should have ZERO volts, but on my two luminas there's about one volt due to the thin wires GM uses.

This means the pump is running on about 2.5 volts less than it should--but it seems to be normal based on GM using 16 gauge wire where they should have used 12 gauge wire.

 

Ok i will check this as soon as i get to the car again. Thanks. Will keep you updated...also one more thing...when i got the car the fuel pump fuse was blown, the one straight off the positive battery terminal. Could that be a clue as to where my issue is? I figured it had something to do with the bad pump.

 

Been reading some forums...they say something about a fuel tank purge valve...what is that? Could that cause my pump to go bad? How do i see if thats the issue or not?

 

https://www.thirdgen.org/forums/post...60-post11.html

Vent valve, i've heard people saying opening the gas cap relieves the pressure in the tank and allows the car to start, never had the issue so i can't verify