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Hey y'all...
I just bought a 1992 GMC Sierra 1500 4x4 v8 5.3L.... Drove fine for 45 minutes then died on me (bought at an auction)... Now, when you try to crank it it backfires. It runs fine when being sprayed with starter fluid but then as soon as its out of starter fluid, back to the issues. Please please please help figure this out, my boyfriend and his dad are both mechanics and have never encountered this! Thanks so so so much in advance!


   
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Location: Oregon
please, don't use starter fluid to keep an engine running. it could damage the engine. It sounds like you either don't have fuel or injector pulse. when you cycle the key from off to run have someone listen over by the gas tank. you should heat the fuel pump turn for 2 seconds. If you hear the fuel pump turn on you should check your fuel injector to see if they are shooting fuel out. if they are not, unplug one of the injectors and put a test light between the two terminals on the wire harness and see if the test light flashes when the engine is cranking. That will tell you is the computer is sending the signal to fire the injectors. once you know which part is not working you can figure what areas to look further


   
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So my boyfriend took the tbi apart and the fuel pressure regulator, cleaned it and put it back together so now it is running but idleing rough... Any guesses?


   
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you should measure the fuel pressure and volume. A bad fuel pump doesn't always stay dead. Many times a fuel pump that is on it's way out will stop functioning when it gets hot. (after running for a while) Then after sitting for a while they will run again. Have a shop do a current ramp test on the fuel pump. Looking at the current waveform of the fuel pump will show the condition of the electrical contacts inside the motor and can show the pump speed too.

Use a flashlight and look at the spray pattern out of the injectors. You should be able to see the spray out of the injector and it should be a very strong spray pattern that spreads out as it heads towards the throttle plate.


   
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