Why is my truck quitting?

I have a '95 Chevy Cheyenne (it’s got a 5.7 V8, manual transmission). A couple of months ago, I was driving, and it shut completely off. I had the garage to come pick it up, told them what it was doing. They let it sit in the shop idling for an hour, and it shut off; they checked it and found nothing wrong, and it started right back up and ran. I picked it up and drove it for a few days, and it shut off again. It’s just like someone flips a switch when it cuts off. I still have electrical power, but the engine shuts off. I put in a brand-new fuel pump, and it continued doing it; the same with a new distributor. I’ve got it back in the shop now, but no one can figure out what the problem is. Any suggestions?

What about fuel filter? Did you replace it? Sometimes they clog up.

Was the ignition module changed at the same time as the distributor? That was a common “quit running for no apparent reason” problem on that vintage of GM.

It might be a good idea to grab a spark tester (a few bucks at your local parts store) so next time it does it you can narrow it down a bit.

Does it always shut off it idle or does it sometimes shut off while moving?

Both-- mostly when the truck moving (it’ll usually turn back on/start back up, though).

If the truck starts right back up after stalling it is very possible you have a loose connection that could be most anywhere. I would inspect your harness plugs especially at the fire wall. A wiggle test can sometime helpnarrow down the problem, You wiggle wires in an attempt to duplicate the problem. A visual inspection with a good bright flash light can sometime reveal corroision in a wire that will usually appear at a connector. I would start with the battery cables and any other large power sources. I have heard of key switches vibrating just enough to switch off an engine also but never seen it first hand.

Do vehicles even have PCV valves any more? That was the culprit on one of my old cars.

Not knowing how electrically savvy you might be, but I would suggest getting a detailed schematic your model year and studying it thoroughly if you plan on doing the repair yourself. That way, you can limit your potential search area from the dozens or hundreds of possible wires that it could be ( I think that you are having an electrical issue myself). The schematic should be available online somewhere or the dealer might be willing to provide you with one.

It may be time to break down and take the car to a shop that specifically deals with automotive electrical issues. They have the experience to chase down difficult problems that most regular shops and even dealerships lack. Unfortunately, they may also tell you something that you don’t want to hear, like that you may need to replace portions of or your entire wire harness due to corrosion.

You have to decide then if the car is worth it to do so.

What about the fuel pump cut off switch. I once had the exact same problem on an old Ford Taurus. The wiring to the cut off switch, located in the trunk, was intermittent.

I had an intermittent stalling problem on my otherwise healthy, low mileage '93 5.7 Silverado. Sounds similar; truck would be running fine but suddenly sputter and die. Wait a few minutes and it would start again and no problem until next time.

I took it to a good diagnostic mechanic I know that traced it to what I seem to recall was a fuel filter (or fuel system part of some sort) on the frame just under the end of the cab. I had already had the fuel filter proper changed; this was something else. You could see the thing on the fuel line if you looked under the vehicle. Sorry I cannot remember the part name, it was a few years ago.

Had a similar problem on my daughters Ford, after lots of parts and misery stumbled on the coil wiring clip.
It was an intermittent problem and those are the hardest problems ever.