Chevrolet Repair: starting problem, throttle position sensor, oil pressure switch

Question
I have a 95 blazer 4.3l vortec eng(w).The fuel pump operates when ignition on,engine cranks ok but won't start.If I prime it with fuel it will start and run.Once turned off it will not start.Fuel filter was changed.Could a fuel pump be bad even though I can hear it operating.

Answer
Hello Alan,
In a word, yes.
I have been in the tank for a low pressure problem, and found a split in the hose that connects the pump to the line, thus spraying the fuel inside the tank.
A pressure test at the engine could save the work of removing the tank.
Your problem could be injector related, either fuse, wires, or lack of signal.
It is possible for a bad throttle position sensor to tell the ecm it is in the clear flood position, and not send fuel. Try unplugging it, although that will set a code, but the engine can run without it.

Now, you say if you prime it, it will run. If it continues to run, then the injectors are ok, and the fuel pump relay may be bad, and the pump running on power from the oil pressure switch.

Hmmmm.

I would sure want to check the fuel pressure with a tester.
14 PSI I believe, and it all needs to be there.

Van