88 Chevy Will start but shuts off. At a Lost need Help

[Schurkey]

I have a 88 C1500 5.7. We just installed a Mild rv cam for a little more torque/hp.

Was the cam degreed when it was installed? If not, is the cranking compression reasonable for your altitude and compression ratio?

It will Fire up it runs for about 3-5 minutes with no issues an then shuts off (as if the key was turned off) ,

Is your scan tool showing that it stalls just after switching from open-loop to closed-loop? Or is it well into closed-loop before it dies?

The Injectors Do Keep pumping till loss of pressure after it dies,

You're saying the engine stalls--the crankshaft STOPS TURNING, but the injectors are still spraying fuel until there's no more fuel pressure? Are the injectors still clicking after the fuel pressure goes away?

If so, we had a guy on this forum--maybe a month ago--that had injector spraying with the engine not turning; his issue was the ignition module, if I remember correctly. I had some trouble believing that...but that's what he said.

Stop changing parts and diagnose your issue(s). You need to put a scanner on it to check stored codes and see what's happening with your sensors' input when this happens.

Yes. Use the scan tool to verify sensors and their wire harnesses (input) AND the computer outputs--ignition advance, IAC, injector operation, etc. along with their wire harnesses.

Maybe use the scan tool to force the computer into "Limp Home" mode, see if it still stalls.

Check for vacuum leaks by spraying brake cleaner (the flammable kind)

I hate seeing folks use brake cleaner for that. The wrong kind releases phosgene gas when it burns, and that's REALLY BAD.

I use aerosol carb spray, not brake spray.

 

[RMH98]

I had a problem on an 88 S10 where it would shut off when it warmed up and went into closed loop. Traced it to a diode in the transmission circuit. As soon as it went closed loop, the computer locked up the converter, and opened the egr, resulting in a big vacuum leak at idle. Put your foot on the brake pedal and see if it stays running (that will keep the converter circuit open so it won’t get a signal to lock up). Mine was a purple wire on the brake pedal switch, just unplugged it, never did dig into the trans. Just a weird fail, but worth a look. Hope it helps.

 

[Brian Shanahan]

Have you checked all the grounds? I know a faulty ground or a loss of ground makes them do some weird things. If it’s not pulling enough ground I would check to see what the alternator is charging at? Is it over charging? Also what’s the compression? Are the valves opening all the way? You said you installed a cam does it or did it require springs?