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Thread: 12 v fuel sender and guage

  1. #1
    Join Date
    Jan 2007
    Fort Smith, Arkansas

    Default 12 v fuel sender and guage

    This can't be rocket science, yet I've screwed it up twice. I have the pickup unit from a 1977 chevy van welded into my stock tank. This gives me a removable unit that has all the extra things like return line, access to inlet sock, and 12v sender.

    I have bought a 0-90 ohm guage twice, installed it, and both times, I get the full reading only. The tank is grounded, the pickup unit is grounded. I am getting some continuity between the sender wire and ground. Not much but it isn't open either. Could this be the source of my trouble? I grounded the sender using one of the vent tubes rather than the rusted out original location on the edge of the ring. Is this acceptable or is the ground supposed to be isolated from that part of the sender?

  2. #2
    Join Date
    Sep 1998
    North Central Wisconsin


    If you run a wire from the gauge to ground the same reading would it does sound like you have a problem at the tank end...unless the gauge is grounded out somehow.

    If you take the sending unit and look carefully, you should be able to follow from the sending unitwire down to the point where the float arms end is...where is sweeps the scale on the sender. From the point where the wire started down to the sweep area is the path hat MUST be isolated from the wherever the gound is hooked up MUST be seperate from everything that the sender wire is attached to.

    Maybe you can take the ground wire from the sweep area and drill a hole in the top of the sender and run the wire out the top and put a little rubber grommet on it to keep it from having any contact with the rest of the sender housing.

    You could be missing a simple rubber ring or gasket or something that is keeping one side from the other too...might take a look at a junkyard unit if you can...

  3. #3
    Join Date
    Jun 2007
    Alexandria KY


    Most fuel guages default to full when grounded. Could the sending wire (the one that sends the resistance signal from the sender to the gauge) be shorted to ground? Could the gauge itself be shorted to ground? What resistance range does the gauge operate in? Usully zero is empty and 90 is full, but some gauges are exactly opposite.
    I think the logic was that it would be better for a defective or ground-shorted gauge to read "EMPTY" instead of "Full" for obvious reasons...

    According to the Snap-on Gauge tester/Signal Generator and Calibrator Manual most 1966-94 GM fuel gauges read 1 ohm @ Empty, 44 ohms @ Mid point, 88 ohms @ Full.
    I could not locate any information listings under "Jeep" or "Kaiser"...but the 1-44-88 scale is the most popular and common listing ......
    '67 M715 '42 GPW '45 MB

  4. #4
    Join Date
    Jan 2007
    Fort Smith, Arkansas


    It's a 0 empty 90 full. I'll try moving the ground from the vent tube. From what you two mentioned, I think that's the problem. Hope I didn't ruin the guage.

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