My 1994 Z28 will crank and run for about 3-5 mins and then just die like you've turned off the key. You let it sit for about 12 hours and it'll crank right up. When it runs for the 3-5mins it runs perfectly. When it dies I have no spark or injector pulse.
I changed the computer out and the car is still doing the same thing. Its not throwing any codes. The VATS has been bypassed and I'm running a Delteq system. I've checked my connections at the opti harness and everything seems fine. I checked the continuity of the entire opti harness no problems there either. I really need some help. This is driving me crazy with my car sitting dead in my driveway. Please help. Thanks

 

Vapor Lock? Fuel injected cars aren't as susceptable(sp?) to it, but who knows. Thats my guess. Let me know what it wasonce the problem is solved.

 

I'm lost on this one.
Could it be the security system? No injector pulse or spark points to a bad PCM but you say that you replaced it. HMMMMMMMMMMM.
Have you tried disconnecting the battery and reconnecting it? That should reset most of your circuits. If you have more than one key, try the other ones. Sometimes the key connection causes problems.

 

FWIW, I used to have problems after a few minutes of run time and they were always related to closed-loop enable. Before I had a programmable setup I would just unplug the 02 sensors to keep it in open loop.

 

It is probably your fuel pump. It is going bad works fine until it heats up and shuts off. It cools down and works again. It is in the gas tank. Good Luck.

 

Check your fuel pump and possibly your lines as well. If it starts right up and runs without misfiring or any codes your ignition system is probably fine. Check your fuel supply first the work from there.

 

I would check your fuel pump but you should still have spark if it was your fuel pump and you said you don't have spark after this happens.

 

Ok I've given up. I'm going to buy a new opti-spark and try that.

 

I think replacing the opti is the wrong approach on this one. The key is.... "No injector pulse". If that's the case, that does NOT point to the opti. That job is a real PITA and you'll need to take the water pump off to get to it. You could check to see if you can get a spark from the coil. If you get spark after the coil, and you can't get one after the opti, then I would replace it. However, if you can't get a spark from the coil, then you wouldn't get one after Opti. Then replacing the opti would be a waste of time.
How did you measure your injector controls? Are you sure there was no pulse?
I would go to a dealer and talk to a technician (don't take your car in). Sometimes those guys are willing to give out really good advise (at least they do in my area).

 

I have a really good idea that it's your ignition module. It may start when its cold but if it over heats then it will shut up and stall til it cools down again. Check it out and let me know.

 

Well I broke down and replaced the opti-spark myself. Considering this was the first time doing this it really wasn't too bad. The worst part was the bolt on the bottom of the water pump hidden behind the air pump pulley. I know it would have been easier had I taken off the air pump and the alternator. But, I didn't want all that hassle. So with some coaxing and alot of cussing I got that bolt out without taking the air pump or alt. off. It can be done. Once I got over that hurdle it was easy. Got the new opti-spark on there with my delteq system and it runs like a champ. Thanks for the encouragement everyone.

 

I am surprised that replacing the OPTI fixed it for you. Did it look worn or wet? I'm glad you got it running. Happy racing...

 

Woooooooooohoooooooooooooo~~ Praise Jah~

 

try the fuel filter if it aint been changed in a while

 

The previous owner had evidently had a problem before because when I got it out he had covered it in permatex. But, I didn't see any signs of dampness. The old opti looked fine...not worn or burned. Once I put the new one in its been running like a champ.