Alright, i am totally lost on this one. Its a 1992 GMC truck....it will be running just fine, then when I let off the gas the truck will just die. It will start up just fine after its been sitting a while, but after it shuts off, it wont start for atleast a few hours. I just replaced the fuel pump and filter, and I can hear the pump running. The truck wont miss fire or spit and sputter when it dies, its like I just turned the key off. Any ideas?

 

A faulty ign module will act like that.

Try to start it with starting fluid to see if it's fuel related.

 

i sprayed starting fluid in it today and then it starts no problem.

 

Seems like you have already covered the usual problematic items with the fuel system. When the eng started with starting fluid, did it continue to run or die after a few seconds?

I'd connect a fuel press gauge to the fuel rail.
After eng is shutdown, watch the fuel press to see if it drops quickly. Watch the fuel injectors for dribbling after shutdown. (I'm assuming it's a TBI eng.)
When it doesn't start, see what the fuel press reads and watch the injectors for a cone-shaped fuel spray pattern.

 

CTS.. I'd almost bet money.

 

I will hook up a pressure gauge tonight...thanks

What is the CTS?? Is it the coolant temp sensor? i am willing to try anything now, this is driving me crazy

BTW....it is a 350 TBI engine if it makes a difference

 

(The comments made by VWDave are opinion based, if I could diagnose the car personally, then it would be fact based. These are educated guesses and are to be held as nothing more.)

Coolant temp sensor makes the car run rich if it is bad, IMO, that is not the problem. If you want to check it, have the car running and pull the socket off of it and see if the car runs better. I would normally guess to be fuel related, although it doesn't show the usual problems. I think it is ignition related.

Do you have a MSD box or something similar? I am thinking something in the ignition system is getting hot, overheating and shutting off. Maybe its too close to the headers, maybe there is a short causing it.

Hope that helps.

 

Have you checked to see if you set any codes? How long does it run before it stalls? Is it under only certain conditions (weather, long streches of h/w driving, bombing up a steep hill, etc.)?