Good morning, great forum you have here. I hope someone can help me with this problem, I'm working on a friends 88 s10 p/up, 2.5 auto. The truck shuts off, you can restart and it'll run for a few seconds and shut off again. We knew it needed a fuel pump because it was whining so we replaced it, didn't fix it. It had a belt tensioner that was bad and making a banging noise and thought the knock sensor might be picking it up, it doesn't have a knock sensor but replaced the tensioner anyway. With the belt off tho, I fired this thing up and the truck ran perfectly. I put the belt back on and it shut off again, I pulled the 2 wire plug off the alt and it ran fine again. I've checked all the wiring pertaining to the alt, out of desperation I replaced the ecm, distributor, the injector was replaced previous to this problem. When this truck starts to shut off, I can see the injector turns on and off a few times before it dies.
I'm all out of ideas and don't know where to go with this thing. Any help you can give will definately be appreciated. Thanks

 

More than likely the computer is shutting down the engine because the altenator is causing overvoltage condition. That will trigger computer shutdown. Test voltage at altenator and if at 14.6 or above you'll need to fix.