Pontiac Repair Questions? Ask a Mechanic for Answers ASAP
Greetings Mike from Mikey at Just Answer!
Fuel pump failure is common on all GM cars and trucks. More so if the driver runs the vehicle low on fuel level frequently.
About 90 percent of the time this type of driveability concern turns out to be a fuel pump failure.
One trick that we use to confirm a bad fuel pump is to hit the center of the fuel tank while someone else is cranking the car over during a no start condition. This is the easiest way to confirm a bad fuel pump. If the car fires right up after you hit the tank, you know the shaking up of the pump got it going again. The fuel pump itself is a high-speed electric DC motor with brushes. Once the brushes wear down, you often get intermittent operation.
If hitting the tank does not get the fuel pump going, remove the ignition key for 25 seconds. Then put the key in and turn it to the on position and watch for the engine light while listening for the fuel pump prime. If you get no check engine light and no fuel pump prime this is a sign of a failing engine computer. Leave the key on for 5 minutes and try again. Watch for a correlation of no fuel pump prime and no engine light to suspect a bad computer.
When the key is out for 25 seconds or more the check engine light should always come on when the key is first turned to the on position.
Otherwise you have to be monitoring the voltage at the fuel pump during a no-start condition to verify the fuel pump is faulty.
Computerized test equipment is needed to properly diagnose a crank with no start condition. Fuel pumps often never give you this opportunity because the car starts every time after a tow.
Some times there can be other component failures like a bad crankshaft position sensor that cause a crank with no start but that requires specialized equipment to perform diagnosis at the time of no-start.
There are times when a car is towed in multiple times only to have no problem detected, on those occasions we will often advise the customer to replace the fuel pump on a guess because towing is expensive and fixes nothing.
When we replace fuel pumps we also replace the relay, the wire connector for the pump and the fuel filter.
If this car was in my shop I would begin by replacing the PCM and fuel pump relays, in the underhood junction box, shown in green on the diagram below.