I have a 99 GMC cargo van with a 5.7L that wont stay running. I did a tuneup on it and has a hard time staying running. it also kills when you put it in gear. Any suggestions would be greatly appreciated

 

Where to start? Did it run okay before the tune up? If so, and if you changed out the spark plug wires, I'd check the order. One may have been switched. If the problem existed before the tune, I'd suspect the fuel pump in the fuel tank. When it fails, it causes the issues you describe.

 

I agree with that. Try and do a pressure and volume test, but if it won't stay running that won't work. I'm leaning heavily towards a faulty fuel pump.

 

You need to check for codes. A bad fuel pump usually just quits, and the van wont start. If you hear it prime when you turn on the key, then its running. As mentioned above it Could be a pressure or volume issue, but that could also mean bad regulator (engine) clogged filter (frame rail drivers side) or faulty poppet valves or injectors (engine).
Too much to chase without a compass.
I had a 2002 and before I sold it, it had a very intermittent issue where I would start the van and it would start normally, but then not idle and ran super rough. The only fix was to shut off the engine, remove the key, and re start. Poof. problem fixed. Gremlins like that can be super hard to find and fix.

 

Good points, the OP (original poster) did not mention any codes. Why not try the lowest common denominator, the fuel filter for $10 or $15 for the part you can eliminate that from the equation. Only problem is with that old of a van, your risking damaging the fuel line, (the nut not coming loose, and twisting the metal fuel line), that would not be good. If you're having the same condition after replacing the fuel filter, then I would do the fuel pressure test. I believe it has to be at least 50 psi with the key on, 49 psi is not good enough. If the pump shows good, that leaves the pressure regulator, located below the plastic intake manifold cover. I don't know how that part is tested.

Fuel filter: 1999 GMC SAVANA 2500 5.7L V8 Fuel Filter | RockAuto

 

I believe his fuel filter has no threaded connection. Its that spring clip push on type. Not fun....lol

 

OK, yes the spring clip type, have that on my Explorer. You know, we are trying to help this guy, but he hasn't replied, I wonder if he's having problems with registering on the forum, or solved the problem already, and forgot to let us know.


You know my fuel filter is inside the tank, 2008 Express 1500 4.3, that's convenient.