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Tiny
CRAIG92481
  • MEMBER
  • 1998 PONTIAC GRAND PRIX
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 90,000 MILES
3.8L fuel pumps prime on key on and after engine dies. Checked all fuses and swaped both pump relays no change. After pump prime pressure is 55 psi car will run for 15 sec. Then dies then pump turns back on to prime system. Engine has no codes, and no know problems. Removed cover to access pump wiring and test light lights durring prime but dose not light when engine is running. Made a jumper and turned on fuel pump and car runs ans nothing wrong. Tested plug and still no power at the pump when car is runnig. I thing the main question is what turns the pump on when engine is running, (ecm, and switches, sensors?)
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Tuesday, July 21st, 2009 AT 9:32 PM

4 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
The PCM is what tells the relay when to send power to the fuel pump. Have you checked for poor terminal connection between the fuel pump relay control circuit and the PCM? Also, using a test light connected to ground, check to see if you are getting power to the ignition feed circuit at the relay. If you are, recheck the contacts to the relay.

Let me know what you find.

Joe
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Saturday, March 20th, 2021 AT 7:31 PM
Tiny
CRAIG92481
  • MEMBER
  • 7 POSTS
After checking the pump and testing several sensors found a ressistor in the right side in the wheel well above the washer fluid bottle was bad. GM has a updated part and location for this ressistor. The way I think this system works is full power, batt voltage to the pump on the prime and when the boost reaches a set level in the computer. All other time the sytem run on a lower voltage when the deman for fuel is lowwer.
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Saturday, March 20th, 2021 AT 7:31 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
That is correct. I'm glad you got it figured out. Let us know in the future if you have any questions, and thanks for using 2carpros. Com
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Saturday, March 20th, 2021 AT 7:31 PM
Tiny
CRAIG92481
  • MEMBER
  • 7 POSTS
Did you know about the resistor, and what would be the real reason for it
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+1
Saturday, March 20th, 2021 AT 7:31 PM

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