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Fule pump / Sending unit problems

Discussion in 'The Garage' started by readymix, Jul 18, 2004.

  1. readymix

    readymix 3/4 ton status

    May 30, 2004
    Likes Received:
    Murrieta, California
    Well i removed the bed and the sending unit from my 87 to see what was wrong and the thing was all normal. 3 Ohms at empty and 94 Ohms at full. I did find that the sending unit and pump are only recieving about 6Vdc input and i though this could be the cause of my faulty fuel gauge readings. What do you guys think.

    I know the gauge works fine because when the sender is removed from the loop the gauge reads full but when it is plugged in the gauge will never read above 3/8 tankwihte the sender at full???
    Any suggestions.
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Dec 13, 2000
    Likes Received:
    Roy WA
    I'd find out why you are only getting 6V to the sending unit. Seems odd to be only 6V, for sure. Guaranteed it should be 12. Check the other end of that wire to make sure it's not getting 12V either.
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Dec 14, 2001
    Likes Received:
    Pleasanton, CA.
    Also, GM sending units are 0-90 ohm. I don't know how big a difference the 3-94 ohm you are getting will make but the sending unit itself usually says the ohm range right on them. Also GM uses grounds to activate things, so if the sending unit wire were to be grounded the gauge would read full.

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