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Fuel Pump won't run when engine does

J

jdonald

New member
Please help


1997 Pontiac Grand Prix GTP 3.8L supercharged

New fuel pump; changed computer, changed fuel filter, changed fuel pump relay

Symptoms:
Scenario 1:
Key on – fuel pump starts for 2 sec. –pressures rack to 52 lbs-then shuts off (normal)
Car starts – computer says “fuel pump on” (normal)
Fuel pump has no power going to it- fuel pressure falls off-car dies
As soon as car dies the fuel pump pressures up and shuts off.
This cycle repeats.
At first after the car would cool down- it would run for a while before stalling

Scenario 2:
Car starts – accelerator is held to the floor
Rev limiter stalls engine at 4000 rpm
Engine slows to about 3000 rpm
Then speeds up to 4000 and stalls
This cycle takes less that 1 sec.- repeats until-
Gas pedal is released, then engine slows down and dies
Fuel pump starts pumps for 2 sec and shuts off

Manual says after the initial 2 sec pump to charge system – the computer waits (while cranking) to receive a “signal” (from where it doesn’t say) to send the “on voltage” to the pump relay. In another place says comp. sends a signal to another before the actual pump relay.
 


jdonald said:
Please help


1997 Pontiac Grand Prix GTP 3.8L supercharged

New fuel pump; changed computer, changed fuel filter, changed fuel pump relay

Symptoms:
Scenario 1:
Key on – fuel pump starts for 2 sec. –pressures rack to 52 lbs-then shuts off (normal)
Car starts – computer says “fuel pump on” (normal)
Fuel pump has no power going to it- fuel pressure falls off-car dies
As soon as car dies the fuel pump pressures up and shuts off.
This cycle repeats.
At first after the car would cool down- it would run for a while before stalling

Scenario 2:
Car starts – accelerator is held to the floor
Rev limiter stalls engine at 4000 rpm
Engine slows to about 3000 rpm
Then speeds up to 4000 and stalls
This cycle takes less that 1 sec.- repeats until-
Gas pedal is released, then engine slows down and dies
Fuel pump starts pumps for 2 sec and shuts off

Manual says after the initial 2 sec pump to charge system – the computer waits (while cranking) to receive a “signal” (from where it doesn’t say) to send the “on voltage” to the pump relay. In another place says comp. sends a signal to another before the actual pump relay.
Click to expand...
this sounds like a fuel pump resistor that's bad. a common problem on these cars.here's a link that might help:Rocky Mountain Club Grand Prix
 
I fixed it. It wasn't the resistor. The signal from the computer wasn't reaching the resistor relay. I shunted the two prongs on the resistor relay so the fuel pump does not run on low speed. It runs at "normal" speed all the time. It works perfect now.
 
jdonald said:
I fixed it. It wasn't the resistor. The signal from the computer wasn't reaching the resistor relay. I shunted the two prongs on the resistor relay so the fuel pump does not run on low speed. It runs at "normal" speed all the time. It works perfect now.
Click to expand...
it runs on high speed now and that's hard on your fuel pump. i still think it's the resistor...
 


I shunted the resistor wires to bypass it and the fuel pump would not run. So, I don't think it's the resistor.
 
I found my problem that had similair simptons and it turned out to be a broken wire on the back of the fuse panel for the pcm and sensor ground. Check the black and white wires coming from B1 and B3 in the black cell. Only after replacing both cam and the crank sensor and bench testing the harness for shorts, did i realize that when i was playing with the warness i was bumping the fuse panel which allowed the car to start until i hit a bump
 


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