I have a 2000 GMC Sierra 4 WD 5.3 liter 126K. The truck stalled one day ( very rare ) and would turn over but not run? Over the course of 3 hours I tried to start it about ten times with no luck. Then I heard a bang when turning over the key ignition? It continued this so I pulled the starter and it was ok reinstalled. Phone a friend…and decided to remove plugs to decrease possible internal pressure.
Engine does turn over with fuel delivery to the cylinders but when you reinstall the plugs the engine returrns to banging and still will not run? Also noted the fuel pump ( fuel pump new 3 months ago) does start when key is advanced in the ignition but it makes a slight whining sound as it finishes it pressuring up. Any help would be greatly appreciated
Problem with the timing of spark -v- valve position maybe? Pushing in fuel but sparking it wrong, like hardly at all? I’m not real familiar with this engine, but this’ll help those in the know, I bet. Also, are you able to determine if engine is pulling in air well when cranked over ( ie creating vacuum in cylinders to pull in air/fuel)? Might be a sensor for cam(s) position or even a chain/belt that moves things together being busted, ime.
If you know a mechanic with a code reader have them scan it. I agree it sounds like the timing is off, possibly a bad crank sensor. Do a Google search on OBD codes for your particular model. Sometimes there’s ways to get the car to output them without a reader (you turn the key off & on a bunch of times and the CHECK ENGINE light will flash in a certain pattern telling you the error code).
I did forget to mention that I have changed the camshaft sensor after this happend with no luck. The possibility of a damaged engine is rare in this instance as the motor will crank over if I decompress the cylinders by removing and reinstalling the plugs?
Please describe the bang. Is it a cylinder firing (a bit like a gunshot)? A metal hammering? Does it happen once per starting attempt, or is it repeated while cranking? If repeated, how rapid is it?
The banging is similar to a single hit of a metal hammer per each attempt to start, just one bang when you turn the key over. If you remove or loosen the plugs so you can decompress the cylinders it will turn over but again it will not start?