Bad fuel pump or bad Relay???
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Junior Member
Joined: Apr 2001
Posts: 82
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From: Belleville Illinois
Bad fuel pump or bad Relay???
Last week, car wouldnt start.
When I turn the key on, the fuel pump doesn't prime.
Went through all the basic steps:
Jumped 12 volts to the tan/white wire at the relay...no pump sounds
Checked fuses at the fuse block and the single lead near the battery, all are good.
Noticed today that the fuel guage is pegged at full even with the key off.
Could this just be a bad fuel pump relay or am I looking at replacing the pump AND the whole sending unit...yikes?
The car ran fine. Has been sitting for some time (1 year) but has been started every week faithfully. I haven't driven the car is a few months tho.
Basic car info:
89 T/A, 305, TPI, no mods, 300,000+ miles
When I turn the key on, the fuel pump doesn't prime.
Went through all the basic steps:
Jumped 12 volts to the tan/white wire at the relay...no pump sounds
Checked fuses at the fuse block and the single lead near the battery, all are good.
Noticed today that the fuel guage is pegged at full even with the key off.
Could this just be a bad fuel pump relay or am I looking at replacing the pump AND the whole sending unit...yikes?
The car ran fine. Has been sitting for some time (1 year) but has been started every week faithfully. I haven't driven the car is a few months tho.
Basic car info:
89 T/A, 305, TPI, no mods, 300,000+ miles
Member
Joined: Apr 2006
Posts: 106
Likes: 0
From: Richmond Hill, GA.
Car: White 1989 Iroc-Z / Teal 91 RS
Engine: V8 350 TPI / V8 305 TBI
I just replaced my fuel pump (in tank). I replaced my relay first! And I could feel it click over! So obviously that was good. I was getting like a good 12 volts from there. The sending sensor (not sure the exact name for it) that mounts on the tank, was getting like 8 volts. Anyways the car would turnover but not start. Had the fuel pump replaced and it starts now. But my oxygen sensor is going out now heh. If you dont hear that little buzz from the fuel pump when you first start it up and the relay is good, its most likely the fuel pump!
Thread Starter
Junior Member
Joined: Apr 2001
Posts: 82
Likes: 0
From: Belleville Illinois
Got that.
I'm just puzzled why the guage is pegged at full...even with the key out. Seems like something s shorted out somewhere.
I'm thinkin I smell a mouse. I'm gonna check all the wiring before I start spending any money.
Old guys, chime in here...
When I check the voltages at the relay, heres what I get:
Key OFF:
Orange- 12v
Red- 0v
Gr/Wh- 0v
Bk/Wh- 0v
Tan/Wh- 0v
Key ON:
Orange- 12v
Red- .01v
Gr/Wh- 0v
Bk/Wh- .02v
Tan/Wh- .01v
I'm just puzzled why the guage is pegged at full...even with the key out. Seems like something s shorted out somewhere.
I'm thinkin I smell a mouse. I'm gonna check all the wiring before I start spending any money.
Old guys, chime in here...
When I check the voltages at the relay, heres what I get:
Key OFF:
Orange- 12v
Red- 0v
Gr/Wh- 0v
Bk/Wh- 0v
Tan/Wh- 0v
Key ON:
Orange- 12v
Red- .01v
Gr/Wh- 0v
Bk/Wh- .02v
Tan/Wh- .01v
Thread Starter
Junior Member
Joined: Apr 2001
Posts: 82
Likes: 0
From: Belleville Illinois
After further checking...
Got a helper...my 13 yo home from school.
Checked voltages at the relay again:
Orange hot vith 12 volts key off and on...sounds normal
Tan White wire 0 voltage with key off, then a 3 second 12 volt spike when the key is turned on...again normal
Its just that the pump is dead and wont respond to the 12 volts or, the wires are grounded out somewhere between the relay and the fuel tank.
The only thing that still has me puzzled is why is my fuel guage pegged past full (it only has 3/4 tank of gas in it).
Got a helper...my 13 yo home from school.
Checked voltages at the relay again:
Orange hot vith 12 volts key off and on...sounds normal
Tan White wire 0 voltage with key off, then a 3 second 12 volt spike when the key is turned on...again normal
Its just that the pump is dead and wont respond to the 12 volts or, the wires are grounded out somewhere between the relay and the fuel tank.
The only thing that still has me puzzled is why is my fuel guage pegged past full (it only has 3/4 tank of gas in it).
Thread Starter
Junior Member
Joined: Apr 2001
Posts: 82
Likes: 0
From: Belleville Illinois
Still puzzled
I'm gonna work this thing through til I absolutely have to replace the pump....
Pulled the carpets in the rear today...
Fold the rear seats foward...
Lift up on the carpet to expose the fuel pump wires where they pass through the sheet metal to the tank..
Fuel guage pegged past full
Wiggled the wires
Fuel guage drops to normal (1/2 tank which I know is correct)
Im thinking a mouse has done a little handi work on my wires.
I live in SW Illinois, and mice are on the move this time of year since the weather is cooling off. I had to poison the few that took up residensce in my garage.
Anyone ever had this happen?
Pulled the carpets in the rear today...
Fold the rear seats foward...
Lift up on the carpet to expose the fuel pump wires where they pass through the sheet metal to the tank..
Fuel guage pegged past full
Wiggled the wires
Fuel guage drops to normal (1/2 tank which I know is correct)
Im thinking a mouse has done a little handi work on my wires.
I live in SW Illinois, and mice are on the move this time of year since the weather is cooling off. I had to poison the few that took up residensce in my garage.
Anyone ever had this happen?
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