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Arench
Arench, Master Technician
Category: Pontiac
Satisfied Customers: 1461
Experience:  28 years experience auto and truck sales and service.
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2004 Pontiac Grand Prix: 3800, 72K miles..start condition..revolutions

Resolved Question:

2004 Pontiac Grand Prix, 3800, 72K miles, Failure to start.
This problem has been going on for quite some time and now is in a no start condition. (Was, read on) At times, the car would start hard, always cracking over and would turn over for several revolutions before starting. Problem would come and go. Yesterday car was warming up in the driveway and just quite running and would not restart. At that time I turned the key from off to run position and would not hear the fuel pump come on for the 3 second priming. No OBD codes are present. After letting the car sit for a several hours, I turned the key to the run position and low-and-behold, the fuel pump primed and the car started. Could the fuel pump have a bad spot in the winding? Might I have a bad fuel pump ground? Fuel pump relay? What are the permissives that need to be met to allow the fuel pump to run?
A relative also has identical vehicle and it to is developing the same conditions. Is this predominate in the 04 3800 Pontiac line? Thanks Mike
Submitted: 4 years ago.
Category: Pontiac
Expert:  Arench replied 4 years ago.

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.

 

graphic

 

 

 

Arench, Master Technician
Category: Pontiac
Satisfied Customers: 1461
Experience: 28 years experience auto and truck sales and service.
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