Fuel gauge and sender operation and diagnosis

Discussion in 'Sparky's corner' started by CJay, Feb 15, 2018.

  1. V8Adam

    V8Adam Well-Known Member

    Thanks for the info, that's useful to know! I will check it out on mine - when it stops raining!
     
  2. John garvey

    John garvey Garv455

    Should gauge go to empty when car is turned off?
     
  3. V8Adam

    V8Adam Well-Known Member

    Good question, I do not know as my gauge has not worked since I purchased the Riv.
     
  4. GSCat-UK

    GSCat-UK Active Member

    Great guide, many thanks.
    I'm having a problem with my fuel reading. Always reads empty, I did the diagnostics on the tan feed wire form the sending unit and all seems well from there back to the gauge (it reads full when disconnected and empty when grounded)
    I also have a good ground from the sender to body so I'm not sure where to turn now, the sender unit is new.
     

    Attached Files:

    Last edited: May 18, 2020
  5. CJay

    CJay Supercar owner Staff Member

    If it always reads empty,, the tan wire is grounding itself someplace. I would examine the short wire from the plug in the trunk to the sender itself. Try running a jumper wire right to the sender itself

    I've also learned that just because a part is new doesn't make it nessecarily good
     
  6. GSCat-UK

    GSCat-UK Active Member

    Cheers, I will have a look. One thing I can't understand though is that if the tan wire is grounding itself wouldn't the fuel gauge read empty , not full when I pull the wire from the sending unit?
     
  7. CJay

    CJay Supercar owner Staff Member

    Your pulling it from the plug in the trunk right? There is a possibility that the wire from the plug to the sender is pinched and grounding itself
     
  8. GSCat-UK

    GSCat-UK Active Member

    Mine has no plug in the trunk, I'm pulling it directly from the sender.
     
  9. CJay

    CJay Supercar owner Staff Member

    Its really a simple circuit. There arent many parts involved here. The next step might be to get behind the gauge and run a wire from the sender right to the back of the gauge
     
  10. V8Adam

    V8Adam Well-Known Member

    Not sure if it will help but this video helped me:
     
    446379H and GSCat-UK like this.
  11. GSCat-UK

    GSCat-UK Active Member

    Many thanks
     
  12. GSCat-UK

    GSCat-UK Active Member

    So, today I pulled the sender from the tank after using up some fuel. I tested it and the ohm readings are correct form empty to full (0 - 90)so the sender good.
    I wired it up in situ, the fuel gauge has come to life but only reads just over 1/4 when float is at full position, when float is half full position the gauge reads half way between empty and a quarter.
     
    Last edited: Jun 8, 2020
  13. V8Adam

    V8Adam Well-Known Member

    Jason will probably be best to chime in on this but I would say that's the gauge. Sounds like the gauge is not reading the resistance correctly and therefore not displaying the correct reading.
     
  14. FLGS400

    FLGS400 Gold Level Contributor

    Jason, I know that this is an old thread, took me a bit to find, but I just wanted to thank you for writing it up. The gas gauge in my car went to the above empty and now I know how to trouble shoot it!
     
  15. lostGS

    lostGS Well-Known Member

    What about when it is full the needle is in the middle of the H in hot. But goes down when you use fuel?

    Anyone have any idea where the sending unit wiring is on a 71 Sportwagon?

    Thanks
    Tim
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The gauge itself may be broken.

    1971 Buick Chassis Manual.

    SportwagonTankR.jpg SportwagonTank2.JPG
     
  17. 12lives

    12lives Control the controllable, let the rest go

    Can anyone recommend a source for a good replacement sender? or brand?
     
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    For what car?
     
  19. 12lives

    12lives Control the controllable, let the rest go

    1970 GS 455, 1967 Special Wagon
     
  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

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