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Strange Fuel Gauge Problem

Discussion in 'The Hokey Ass Message Board' started by blown240, Jan 6, 2011.

  1. blown240
    Joined: Aug 2, 2005
    Posts: 1,654

    blown240
    Member
    from So-cal

    Here is a wierd one that I have never heard of. When my 66 GMC is stopped the fuel gauge works perfect. But when I am moving, at any speed, the gauge goes to full and bounces around a tiny bit.

    It makes sense to me that maybe its a short somewhere on the sender wire, but I dont know.

    Any Ideas?
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 49,315

    squirrel
    Member

    going to empty and staying there indicates a short. Going past full indicates an open circuit. Could be a loose wire from the tank to the gage, or a crack in the dash printed circuit, or a loose connector at the dash, or the strap in the tank (the part of the sender that connects the resistor to the screw terminal) is broken or something, or it could be the sender resistor is broken. I would suspect the sender.
     
  3. First check for a loose connection then when that isn't it buy a new sender and run a new wire from it to the gauge.

    I have a wierder problem for ya. I once had a '62 short bed that you could use the fuel gauge like a tach. At idle it showed empty and when you gassed it it moved to full. I never did figure it out, just carried a jerry can.
     
  4. blown240
    Joined: Aug 2, 2005
    Posts: 1,654

    blown240
    Member
    from So-cal

    Thanks for the info. All the othet gauges work, so I am going to start by checking for loose wires, then check the sender.
     

  5. jaz
    Joined: Dec 16, 2010
    Posts: 218

    jaz
    Member
    from London, UK

    That would have been your voltage regulator not working properly - the faster the generator was spinning the greater volts where hitting the gauge making it read full - had the same problem on my Mercury

    Also, I would have a full tank reading, but the more things I turned on eg. Lights, Fans, music, etc the emptier the tank got as voltage dropped - I too carried a jerry can with me as I never had a clue how much fuel I had - LOL

    New voltage regulator cured it

    Could be the same problem for blown240?
     
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 49,315

    squirrel
    Member

    not likely....the GM senders from back then are notorious for having an open circuit in them. Those early printed circuit gage clusters are not known for being reliable either.
     
  7. medicinal_marinara
    Joined: Nov 24, 2009
    Posts: 139

    medicinal_marinara
    Member
    from Oregon

    GM fuel gauges are bridge type circuits and aren't sensitive to voltage unless the gauge is defective. Ford gauges use a voltage regulator for the gauge cluster and are fairly sensitive to voltage if that regulator is messed up.
     
  8. Check the ground .
     

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