2000 Pontiac Grand Prix fuel pump post earlier

Tiny
DLOWERY513
  • MEMBER
  • 2000 PONTIAC GRAND PRIX
  • 3.1L
  • V6
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
SORRY I forgot to mention that before I even replaced the FUEL PUMP, I noticed
the FUEL GAUGE was all the way up on Full, and the TANK was less than 1/2 full
Do you
have the same problem?
Yes
No
Thursday, November 6th, 2014 AT 7:12 PM

4 Replies

Tiny
CARADIODOC
  • EXPERT
You need to post any replies or followups to your original post. With this new post, no one knows what the original question was or what tests have already been done, and the results. You can fill me in here too if you want to, but I'm not an expert on your car model. You're better off adding to your first post and hope Saturntech9 sees it.
Was this
answer
helpful?
Yes
No
Thursday, November 6th, 2014 AT 7:52 PM
Tiny
CARADIODOC
  • EXPERT
OOPS! Saturntech9 is a good guy, but I was thinking about a previous post I just read for a Saturn. I'll still try to help if you if the problem is electrical in nature.
Was this
answer
helpful?
Yes
No
Thursday, November 6th, 2014 AT 7:54 PM
Tiny
DLOWERY513
  • MEMBER
OK thank you I'm new to this site, so my 2000 Gran Prix SE 3.1
the blower motor stopped working, I replaced the heater blower motor and resistor, They work fine now in all speeds, But now the engine will not start,
Engine is getting fire but NOT Fuel, It will Start for a sec. When I spray the throttle body, So I noticed my FUEL gauge was all the way UP on FULL
when the tank was less than 1/2 full, I checked both fuse boxes and all fuses show OK, I replaced the fuel pump RELAY still nothing, I by passed
The fuel PUMP RESISTOR, and still nothing, SO I replaced the FUEL
PUMP, still I can't hear the PUMP PRIME when I turn the KEY to ON. I
tested the pump running it directly from +bat to - bat to the pump it made a humming noise but not the CLICKING noise that I used to hear CAN this
issue be in my ignition switch, The ignition switch has been getting difficult
to get to the ON position in the last few weeks. Does this sound like anything you are familiar with? Thank you very much. Don
Was this
answer
helpful?
Yes
No
Thursday, November 6th, 2014 AT 8:31 PM
Tiny
CARADIODOC
  • EXPERT
You're describing multiple symptoms that could be related but it's hard to know for sure. Years ago GM had an unusual fuel gauge circuit that used the sending unit in the tank to ground the signal wire and pull the gauge down to "empty". When the ground was lost, typically due to a corroded wire, the gauge would read "full" all the time.

On your car the fuel level sending unit is an input to the Engine Computer, then the computer shares that information with another computer module, the instrument cluster. The sending unit shares a ground circuit with the fuel tank pressure sensor so a bad ground should set a fault code related to that sensor. If you have access to a scanner, you can read the stored diagnostic fault codes to see if there is one related to that sensor.

You could also unplug the connector at the gas tank, verify the fuel gauge still reads "full", then jump the two sending unit wires together. If that makes the gauge read "empty", suspect the sending unit. The two wires to jump are the purple to the black / white.

For the fuel pump, lets start at the relay because that will let us split the circuit in half to see which half has the problem. You can pop the cover off your old one and install it that way, then squeeze the contact. A helper should hear the pump run when you do that. If it runs, all that wiring is okay and we have to look at what controls the relay. If the pump doesn't run, check for voltage feeding the relay first. That will be on terminal 30 or 87. If it's missing, there's a blown 15 amp fuse. I'm not aware of a resistor in that circuit.

You can also bypass the fuel pump relay with a jumper wire or stretched-out paper clip. Remove the relay, then connect terminals 30 and 87 in the socket. You should see a little spark there when you make the connection, and the pump should run.
Was this
answer
helpful?
Yes
No
Thursday, November 6th, 2014 AT 9:39 PM

Please login or register to post a reply.

Recommended Guides