Testing power to fuel pump

Tiny
DLOWERY513
  • MEMBER
  • 2000 PONTIAC GRAND PRIX
  • 3.1L
  • V6
  • FWD
  • AUTOMATIC
  • 150,000 MILES
I replaced the fuel pump relay in fuse box, checked all fuses are ok, I replaced the fuel pump still I hear NO pump priming or running, Could this be the fuel pump resistor? And can I test the power to the pump and the resistor before replacing the resistor? Any help would be most appreciated, I can't afford dealer prices. Thank you POOR
ole boy .
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Tuesday, November 4th, 2014 AT 8:24 AM

15 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
First, check to see if there is power to the pump. If there is, check for a bad ground. The pumps go out all the time in these cars here is a guide to show you what you are in for when doing the job and diagrams to show you what it will be like for your car.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Check out the diagrams (Below). Please let us know what you find.

Cheers
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Tuesday, November 4th, 2014 AT 8:49 AM
Tiny
DLOWERY513
  • MEMBER
I replaced the pump, engine started right up I love this site. Thanks again.
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Wednesday, November 5th, 2014 AT 12:31 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Good to hear, please use 2CarPros anytime we are here to help.

Cheers
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Wednesday, November 5th, 2014 AT 6:00 PM
Tiny
CRAIG92481
  • MEMBER
  • 1998 PONTIAC GRAND PRIX
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 96,000 MILES
Pressure tests at 55-60, during prime. Start engine and pressure drops to 15psi engine dies, then pump reprimes back to 55-60. What would stop the pump from pumping while engine is running, does it sound like a oil pressure switch
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Tuesday, August 28th, 2018 AT 11:14 AM (Merged)
Tiny
MMPRINCE4000
  • EXPERT
Check fuel pump relay and also check the fuel pressure regulator. Disconnect FPR vacuum line, if gas is present, the FPR diaphram is ruptured.

Do you have a security light on?
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
CRAIG92481
  • MEMBER
I swapped the 2 relays and there was not any change. There is not a security light on. I jumped the fuel pump and the car runs fine, but there is still no power to the plug for the pump. I only have the power for the 3 second primes.
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
MMPRINCE4000
  • EXPERT
If you jumped the pump to run off battery voltage and it runs fine, then the pump is OK.

The problem lies in the pump wiring harness, or oil pressure sending unit which serves as a backup to the FP relay.

The oil pump sending unit is designed as a backup to FP relay, but not designed to run pump all the time.

I would replace the OP sender, if problem persists, then you will have to get into the harness and check for open/shorted wires.
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
CRAIG92481
  • MEMBER
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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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
MANX46V
  • MEMBER
  • 1998 PONTIAC GRAND PRIXPONTIAC GRAND PRIX
02 Pontiac Grand Prix 40th Anniv. GTP
29,000 miles. All routine maintance up to date.
Engine has fire (a shot of ether will cause a brief enging run). I can't hear the fuel pump turn on, the fuse is good. How do I test the relay, locate the fuel filter, etc?

The replacement pump assembly is over $300. I've not found good information on the replacement (if needed) instructions. I need to do the repair myself as I am unemployed.

Before the engine quit it exhibited an almost running spit & sputter condition before failing to ignite at all.
Edmonds. Com reports "NHTSA Expands Probe of Supercharged GM Cars." (A high number of engine fires) I am concerned!
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
RASMATAZ
  • MEMBER
Even if it turns On, it has to produce the correct pressure to function properly. You need to check the fuel pressure to rule out the regulator/pump.
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
MMPRINCE4000
  • EXPERT
Generally on supercharged engines, as vacuum goes to boost, the fuel pressure increases as well as injector pulse width.

Air/fuel ratio goes to 12.5:1 or alittle lower to prevent a lean condition.

A lean condition on a super/turbo/nitrous is an immediate burnt piston as combustion temps skyrocket.
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
CRAIG92481
  • MEMBER
Then what would be the reason to ad a resistor to the fuel pump feed during normal operation.
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
MMPRINCE4000
  • EXPERT
Less resistance would increase voltage, more would decrease.

Like LED bulbs, a resistor is added inline on a non LED light circuit to reduce voltage in order not to blow a fuse, since LED's require much less voltage than incandesent.
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
DASIMPFAN
  • MEMBER
  • 1993 PONTIAC GRAND PRIX
I have a '93 Grand Prix 3.1L. After replacing the tranny, the engine wouldn't start. The engine ran perfectly before the tranny swap and now it doesn't. It has tested good for spark, but I found that it wasn't getting fuel. I found that with the ignition on, the fuel pump gets no power; but when I applied 12V of power to the fuel pump, it turns on and pressurizes the system. Still not knowing what the problem was, I tried cranking the engine with the fuel pump on and still it doesn't start. The fuel rail had 40-46 psi of fuel, so I figure the injectors must be shut down for some reason. Does anyone know what I could have damaged or messed with that would cut power to the fuel pump and injectors? I've swapped ecu's to no avail, and also whenever you crank the engine the speedo and temp gauge needles shoot right to their maximum readings until I stop cranking. Any help would be great!
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)
Tiny
XBORNKILLA2K4
  • MEMBER
It seems u have a bad ground for the temp and tach gauges and I would check the sfi fuse or rely for injectors
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Tuesday, August 28th, 2018 AT 11:15 AM (Merged)

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