How do I fix and 97 GMC 1/2 ton with a 350 vortec. Runs great once running. Sat for 5 years. If sits more than 5 minutes wont start without shot of starer fluid

Clean out your egr valve.

Lots of black smoke in the back i had a few problem like that it was the spider in the intake there a central injection system in it its 6 plastic pipe that goes to the cylinder 1 per cylinder 1 or 2 pipe crack and spray gas in the intake your oil must smeel like gas even if its not old let me no after that your car gonna run like new its not a cheap part but you got no choise thats for the question james

Try spraying a couple shots of carb spray down the throttle body while a helper cranks it over. If it starts and runs for a couple of seconds check fuel pressure and the resistance of the injectors.

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Check fuel pressure it should be at least 52 psi if anything less replace fuel pump.If pressure is good then pull vacuum line off of the fuel pressure regulator and if fuel runs out replace regulator.

Is it a ping or a knock? It could be the initial timing is not set correctly. Are you losing coolant? It could be a leaking head gasket and is leaking a small amount of anti-freeze into one of the cylinders. If it is a bearing it will get worse and worse, is the oil pressure good? I guess I'd take it back to the rebuilder.

future reference brake cleaner isn't good to use on mass air. use mass air sensor cleaner or electical cleaner

Try a new distributer cap and rotor button before you go any further.

have the converter checked it may be partially clogged

You will need to do a fuel pump pressure leak-down test, the pump must not loose more than 5 PSI overnight, u will need a cheap fuel pressure test guage, the test port is on the fuel supply rail to the injectors on the intake manifold, it looks like a tire valve but metal with a plastic cap on it, u may be able to borrow this guage from Kragen, Autozone or a parts store like them, if not they are very cheap, less than $20 US. Run the engine with the test guage hooked up, turn off the engine and then check it in an hour or so, if it drops more than 5 PSI then u will need to replace the fuel pump in the gas tank. One note make sure the connection for the guage is tight with no leakage or the test is invalid

Had the same problem with my '96 Silverado with 350 Vortec. The truck would only crank. It would start if fuel was poured down the throttle body. Could not hear the fuel pump hum. Fuse was good, but could not hear relay click. Relay was good, Did some electrical wiring trouble shooting. Turned out that one of the connectors that clasp onto one of the pins of the fuel pump relay wasn't making a good connection, too loose. I just stuck a peice of wire into the connector and pushed the relay back in. Relay clicked, Truck Started. It's been more than 4 yrs. since I made that McGuyver fix. Still firing.