gas gauge

Discussion in 'Troubleshooting & Diagnosis' started by Scrappy1980, Nov 7, 2019.

  1. Scrappy1980

    Scrappy1980 Member

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    My gas gauge was working fine one minute and not the next, it is going way past the F almost to the middle. Is there anything i should check out before dropping the fuel tank?
     
  2. grzewnicki

    grzewnicki Veteran Member Lifetime Gold Member

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    [​IMG]
     
  3. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    ^+1

    You have an open circuit. (At the sending unit ground or the wire to the sending unit.)

    A gas gauge is an Ohm meter, it measures electrical resistance at the sending unit.
    Reading "Past Full" shows the resistance is "infinite", meaning you have a bad connection.
     
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  4. Scrappy1980

    Scrappy1980 Member

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    Thanks,you all have given me a starting point. Why do i know deep down inside it will be at the tank?
     
  5. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    Look for the black ground wire coming from the top of the tank and check its connection to the body first.
    (It's the easiest part of that circuit to repair.)
     
  6. Gary S

    Gary S Administrator Lifetime Gold Member

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    Also, check the wiring connector inside the trunk. The open circuit could be there.
     
  7. grzewnicki

    grzewnicki Veteran Member Lifetime Gold Member

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    The ground wire for the sending unit is under the filler neck and towards the passenger side (at least on a 1972), It has a small sheet metal bolt that holds it to body skin, it is connected to the sender by a little crimp tab built onto the body of the sender, if you have an ohm meter you can check the end of the ground wire (disconnected from body now) to the body of the fuel tank, you should have continuity, you can also disconnect the tan wire inside the trunk where it exits on the sheet metal hump and check it through the sender to the end of the ground wire. On the fuse panel there is a long skinny connector that clips in, that is your harness to the rear of the car, you can check the tan wire there all the way to the end of the ground wire (again disconnected from car body) and see if you have continuity. That will verify everything from that connector through the sender to the end of the ground wire is good.
     

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