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Hot Rods Need help diagnosing a non-functional fuel gauge

Discussion in 'The Hokey Ass Message Board' started by dmac620, Apr 9, 2016.

  1. dmac620
    Joined: Sep 16, 2007
    Posts: 357


    I'm hoping someone can help me with a very frustrating non-working fuel gauge in my 52 Chevy Styleline. Here is the background... I updated the vehicle to 12 volts, installed a 12 volt replacement fuel gauge in the factory dash, new sender in the new poly gas tank, and ran a new wire from the sender to the gauge for good measure. I also ran a ground wire from the tank sender in the poly tank to a the underside floor of the trunk. The replacement gauge is for a 12 volt system so no in-line voltage reducer is needed to reduce it to 6 volts. Lastly, i added about 8 gallons of fuel to the new tank.

    Here's where i am now...
    1) When i turn the key to the one position the fuel needle dropped to empty and stayed there, even when the key was turned off.
    2) If i turn the key to the on position and remove the ground wire that goes from the tank sender to the trunk floor, the needle jumps to to full. If i leave the ground wire off and turn the key off, the needle drops to half full. Turn the key back on, it jumps to full. Reattach the ground wire at the sender and it goes back to empty.

    I trying to figure out where the problem lies... the sender or the gauge? Any other tests i can do to single out the issue?
  2. F&J
    Joined: Apr 5, 2007
    Posts: 13,223


    Normal first test is to ground out the wire at the tank that goes to the sender. It should go overfull(pegged)

    Don't worry about how the gauge reacts with key off, some brands act differently
  3. saltflats
    Joined: Aug 14, 2007
    Posts: 10,676

    from Missouri

    Are the gauge and sender matched for the Ohms
  4. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    from Wisconsin

    I'd guess the wrong sender for the gauge. One type of gauge goes to empty if the sender wire is grounded and the other goes to full. I had a potentiometer that I used to test them with. I think it was 100 ohms. They might make a universal sending unit that the float arm can be switched.

    The factory GM gauges read empty when the sending unit lead is grounded. With 30 ohms of resistance it should read full.

    Depending on what the replacement gauge is, it could be different.

    Here's a link

  5. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    did you make sure the wires on the gauge are on the correct posts ??? and how much fuel is in the tank as some senders if they are the float type and the tank is empty can over extend and short the unit out and make it read goofy as its a short circuit
  6. You didn't say here, but there have been goofy readings noted, after the 12 volt dash gas gauge units were purchased from N.C.A., for 1951 and 1952 Chevys.
    The N.C.A. gauge is a $74.00 unit, much more expensive than the $10.00 reducer, which has served its purpose well, for many years.

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