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Fuel Gauge

Discussion in 'Tech Discussion' started by Marcos, Sep 12, 2019.

  1. Marcos

    Marcos Full Access Member

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    I have a fuel Gauge on my 1980 Jimmy that doesn't work. Id like to get it working again. Anyone have any insight what I need to check? not sure if I need to drop my tank and check anything in there or if theres any electrical I should be checking under the Jimmy?

    thank you
     
  2. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Is it doing anything, or is completely dead?
     
  3. C10MixMaster

    C10MixMaster Full Access Member

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    No sure on a jimmy but on the pickups there is a wire at the starter. its a weatherproof spade connector. It will be the single wire that runs to the back of the truck. disconnect it. Use an ohm meter to check the ohms on the wire to the tank.

    FUEL LEVEL GAUGE PARAMETERS
    For Truck Years: 1967 - 1990
    The Fuel Gauge Needle Should Point to:
    Left Line (Empty) when sender resistance = ~1 Ω
    Middle Line (Half) when sender resistance = 44 Ω
    Right Line (Full) when sender resistance = 88 Ω

    if its not within these parameters you have have a sender problem.

    if that looks good, ground the wire that goes to the gauge. turn the key on engine off. It should show empty when grounded and overfull when not connected to anything. if it fails that test you have a gauge problem.

    a gauge that always shows empty could have a bad float. a gauge that always reads over full could have a bad wire or ground.
     
  4. Marcos

    Marcos Full Access Member

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    the needle always sits at the 1/4 tank mark.

    C10mixmaster ill give that a try and update you.

    Appreciate the info

    thank you
     
  5. AuroraGirl

    AuroraGirl Full Access Member

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    My gauge actually points past full... by quite a bit. Is it possible the needle is "off track" and needs to be pushed over into normal area?
     
  6. Frankenchevy

    Frankenchevy . Supporting Member

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    Where’s it at when the tank is completely empty?

    Could be a bent/worn sender, possible wire issue causing increased resistance, or bad gauge.
     
  7. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Mine was like that, and the sender was no good. I haven’t had a gauge problem, but if the fuel gauge works, and you move it with your finger, it’ll just run right back to where it was before.
     
    eskimomann209 likes this.
  8. thecantaloupeman

    thecantaloupeman Full Access Member

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    Thanks for this. I've been having a similar issue. My tank reads overfull.

    Sent from my SM-G950U using Tapatalk
     
  9. eskimomann209

    eskimomann209 Full Access Member

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    This is correct. But you can pull the needle and re seat it.
    Wouldn’t recommend it they’re brittle. Id check grounds ( mainly one inside frame where the tank hangs) and 12v at the gauge and signal. If you have that you should have everything. You can measure resistance at the cluster plug to see about where it should be, I filled mine up and then read it so I knew exactly what it should read.
    I finally got al my gauges working after a lot of fussing
     
  10. Dmack

    Dmack Full Access Member

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    If it rests last full, at 3 o'clock, it usually means you have an open circuit. Generally a broken or disconnected wire, or broken sending unit connection, as some mentioned before.
     
  11. C10MixMaster

    C10MixMaster Full Access Member

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    sounds like a bad gauge. However check to make sure you have power and ground to the gauge before you replace it.
     
  12. Papa John

    Papa John Member

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    Had same issue on my 82 c10 gauge was working then it stopped right below half mark. Filled it back up today still in same spot.
     
  13. Kim Burke

    Kim Burke Supporting Member Supporting Member

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    First of all, I fought these squarebody fuel tanks for the better part of 6 mos. and still don’t know if mine are “exactly” right. So I’m not the expert but this I do know, ohms = resistance so splices have to been weather proofed or the corrosion will severely effect the accuracy/consistency. Check your connections.
    You’re in the right forum, there are some really sharp patient guys on here.
     
  14. C10MixMaster

    C10MixMaster Full Access Member

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    Yes add resistance and the gauge will read hi.
     
  15. Papa John

    Papa John Member

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    but what would cause it to work then stop just below half all of sudden. I did wash the body of the truck about 2 weeks ago but other than that no other events or changes ? I ran it bone dry and then filled it up and gauge reads the same ?
     

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