1986 Iroc Z
TPI
When I drive the car for a while, shut it off, it won't restart again for an hour or two. When it does this, I notice the fuel pump does not prime when I turn the key on. I replaced the fuel pump relay yesterday, and it did it again today. I checked the voltage coming out of the relay to the pump and it reads around 12v and I can hear the relay clicking at the correct time. All these signs point toward bad fuel pump.
I guess my question is... will the fuel pump act like that when it is going out? I ran a fuel pressure gauge on it and while it is running, the fuel pressure is fine. But I turn the car off, and then attempt a restart immediately and no fuel pump. In my experience, when the fuel pump is going out, it will start cutting out whenever it damn well pleases, not wait for me to shut the car off and back on again.

 

iceman02,

When my fuel pump was going out, my car would frequently surge and/or die... especially when I hit the gas pedal.
My fuel pump is in the tank, so I took the car to GM... about $600+ later it was fixed.

Sorry, but I don't have enough technical know-how to tell you what is causing your problem. However, based upon what happened to me, it doesn't sound like the fuel pump is bad - especially if the fuel pressure is stable.

Just my 2 cents.

Hopefully, someone in this forum can offer more advice (hint)

Best of luck!

 

You know, that's why it sounds like an odd problem to be the fuel pump. In my truck, when the pump was going out, I experienced the same symptoms that you described. Last time it went out in the Iroc, it would just die randomly whenever the fuel pump got hot enough. Let it sit and cool for an hour, start it up and drive it home.
This damn think has gotten so predictable by now. Drive it for 20 minutes or so, shut it off, wait a minute or two, try to start it.... no fuel pump. Let it sit for an hour, everything back to normal.
Well, I guess I'll know by tomorrow..... I'm half done with replacing the pump now. I'm going to replace and resolder the wiring inside the tank going to the pump to rule that out, too.

 

Fixed it. Man, failing fuel pumps sure do exhibit some wierd symptoms.
Here's my best guess. When checking the voltage out of the fuel pump relay was about 12.5v with the car running, when the pump primed (with the engine off) it's only getting 11.5v. When starting the car with the fuel pump cool, the 11.5v was enough to run the pump. Once the fuel pump got hot after driving, the 12.5v was enough voltage to keep the pump running. But when I shut the car off, and attempted a restart (and the pump was hot), the 11.5v supplied was not enough to run the pump. This would explain why I needed to let the car sit for an hour or two before the pump would work again.