I had two different mechanics try to fix what appeared to be a fuel supply problem. Mechanic 1 put in a new fuel pump and the car ran good for 1 day, then failed to start just as before. Mechanic 2 put is a new fuel sending unit (?) then the car failed immediately to start. He dropped the tank again and thought it was the car’s electrical supply (connector) to the fuel pump. I am not sure he replaced it with a new one or just cleaned it up. The car ran for 1 week, then failed to start just like before. He also tested the oil sending unit saying it could disable a fuel pump as a failsafe measure to prevent running without oil, but he said it is good. Also,someone is suggesting that it may need a new coil. Have you heard of a problem like this before?
Oh yes. Somebody should read up about the system operation. If the computer doesn’t know the engine is turning, it might not let the pump run. Then there are always the codes, if any, that a scanner could detect.
It’s at least possible that your mechanics have been guessing a bit up to this point. If a fuel pump is suspected to be inoperative all they have to do is connect a fuel pressure gauge and then run a jumper wire to the pump test connector under the hood.
If the pump and engine runs then the pump is good.
If it still doesn’t run then it’s time to do some real diagnosing.
The fuel pump relay is controlled by the ECM (computer) which controls the relay based on input from the electronic ignition.
As far as I know, GM did away with that oil pressure operated pump cutout a million years ago and really, the pump control system is not that complicated.
So have either one of these guys scanned the car at all? Some problems may show up as a code; others won’t.