Fuel Guage Pegged

Discussion in 'Gauge, Speedo & Instrumentation' started by 82chevy350, Feb 27, 2012.

  1. 82chevy350

    82chevy350 Full Access Member

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    On my 76 the Fuel gauge pegged out past full.
    When i turn the truck on i can see the gauge move a hair but when i shut it off nothing happens..
    I can bang on the dash repeatedly and the gauge will move more towards where it should be.
    But when i turn it on again it pegs out.
    Bad Ground?
    Bad Gauge?
    Sending unit?
     
  2. oneluckypops

    oneluckypops Full Access Member

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    printed circuit borad would be the first thing i would check
     
  3. Tyger13us

    Tyger13us Full Access Member

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    when my truck does that its always a bad connection where the gauge wire connects to the tank sending unit.

    if its not there next thing i would look into would be the sending unit in the tank..

    im guessing it a single tank setup......
     
  4. bucket

    bucket Super Moderator Staff Member

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    My '79 had all sorts of fuel gauge problems when I bought it, it has dual tanks. First, the valve did not switch but it was just a bad fuse. The gauge didn't work at all either, put in a new gauge and it was then pegged way past full. Found a rubber harness plug was undone at the firewall... connected it and the gauge worked for the passenger tank. The driver side tank still read way past full, but it turns out the sender is off a bit and the tank was full. When empty, the gauge still reads 1/4 full.
     
  5. matthew.w.mickey

    matthew.w.mickey Junior Member

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    Hey both my tanks do that its the sending units in the tank Im still trying ti fix it doesnt help that my truck is my everyday go work for uncle sam rider
     
  6. oneluckypops

    oneluckypops Full Access Member

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    Hello!!!!!!! people read his post the part in red. If it was the sending units banging on the dash would do NOTHING. The problem lyes at eaither 1 of 2 spots 1 the gauge itself or 2 the Printed Circuit board on the back of the cluster.
     
  7. 82chevy350

    82chevy350 Full Access Member

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    But remember it only moves when the ignition is off but when the ignition is on i can beat on it all day long and it wont move just pegs out..

    Now when i turn on it still pegs out but when i turn it off it will go to full mark and stop turn it on again it pegs out..

    Im really thinking its a bad gauge.
     
  8. crazy4offroad

    crazy4offroad Full Access Member

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    Remove the cluster and check the metal clips that hold the fuel gauge to the housing and make the contact between the gauge and printed circuit. Mine was kind of loose once, had to do some scraping with a pocket knife and pinch the clips tighter with pliers. Reassembled and it worked fine after that.
     
  9. bucket

    bucket Super Moderator Staff Member

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    Not really. Banging on the dash will often cause even a good working fuel gauge to wander around a bit. Gauge pegged past full is a loss of ground, and with the age of these trucks loss of ground is usually (notice I didn't say always) caused by the ground wire from the sending unit. It will either be corroded right off, or the eyelet needs scraped clean where it bolts to the top of the frame rail.
     
  10. oneluckypops

    oneluckypops Full Access Member

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    Rather the gauge will move or not is NOT the issue. The reason I said to start with the gauge and or circuit board, is the same principal as if you were to jiggle the ground wire at the tank. If the Gauge started fluxuating from jiggling the wire back there common sense tells you to start there. Its the same thing when you bang on the dash, you are jarring either the gauge itself, the circuit board, or even the connector for the instrument cluster.
     
  11. bucket

    bucket Super Moderator Staff Member

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    I get what you are saying, I just don't think it's as obvious as a clue as you do.

    One other thing I forgot to mention. The ground on the printed circuit snakes around all over the place, so when there's a bad spot, it usually makes a bunch of stuff go wacky, not just one gauge.
     
  12. oneluckypops

    oneluckypops Full Access Member

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    uh i dont think that i totally correct. I could be wrong, but I was THINKING if memory serves me correct the fuel gauge should lave 3 terminals, Power, Ground, and a signal wire (which is also ground) If the signal wire is the loose ground then no it will NOT effect any other gauges as it is not a common ground. Now if its a power or the other ground wire it would entirely depend on how the circuits run and where they enter the fuel gauge to know for sure which ones would be Inop.
     
  13. 82chevy350

    82chevy350 Full Access Member

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    ok so now with the truck off the gauge is pegged but i can pull my parking lights on and it will go to the correct level.
     
  14. bucket

    bucket Super Moderator Staff Member

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    I think we were on the same page, more or less. I just wanted to point out that banging on the dash will often make even a good gauge flicker a little.

    Now that right there certainly makes it sound like the printed circuit is the issue.
     
  15. crazy4offroad

    crazy4offroad Full Access Member

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    The negative that loops all the way around the circuit should have a black wire connection at both ends, so that if it breaks in one place in the middle somewhere only one or even no gauges/lights will be affected.
     

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