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Gas Gauge Issue

Discussion in 'Intermediate CJ-5/6/7/8' started by Dale Boyd, Sep 16, 2019.

  1. Sep 16, 2019
    Dale Boyd

    Dale Boyd New Member

    Pekin, Indiana
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    Trying to get the last non-functioning gauge working again. 71 CJ5 w/Dauntless V6. When I got it the PO had replaced the original rear fuel tank and skid plate with a home made tank made from steel plate. I originally had purchased a replacement fuel sender, but the one I pulled out of the tank did not look anything like the replacement I purchased. I measured the resistance of the unit I pulled out, and it did not change as I moved the arm.

    I then purchased a universal VDO sending unit. Before installing in the tank I hooked up the fuel gauge wire and ground wire to the terminals and manually moved the float. The gauge responded as intended, so it appeared the new sender would solve the problem. I bolted the new sender in place, reattached the fuel gauge and ground wires, and hung the tank. After filling up the tank, the fuel gauge still shows empty. I notice a slight movement when I turn the ignition on, but nowhere like it was when I moved the arm outside of the tank.

    Anyone have an idea why the sender would work outside the tank, but not when it was inside? Grounding should not be an issue, as the sender has a ground terminal on it which I used to successfully test it outside of the tank. It almost seems like the gas in the tank is not moving the arm up at all.
     
  2. Sep 16, 2019
    rusty

    rusty Well-Known Member

    norfolk,va
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    Could be the float is full of gas or jammed on something in the tank.
     
  3. Sep 16, 2019
    rusty

    rusty Well-Known Member

    norfolk,va
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    Thinking, does the gauge ground to the dash?
     
  4. Sep 16, 2019
    Lee Bennett

    Lee Bennett Banned

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    Does the gauge get its power from the CVR?
     
  5. Sep 16, 2019
    timgr

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

    Medford Mass USA
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    Yes. The CVR needs a ground to cycle and thereby regulate. Could be the magic smoke has escaped from the gauge or CVR, but I would test with some resistors first. Likely the CVR is performing properly, since the temperature gauge works. The TSM tells you what resistances the gauge expects (10 to 90? something like that), and you clip in each of those in place of the sender to watch the gauge response. Note that your replacement sender must match those values for full, half and empty - there are different types of sender. Measure the resistance with the sender in place and compare with the expected value for however much gas is in there. I'd also check that there is no fault in the wiring between the sender and the gauge.
     
  6. Sep 16, 2019
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    What is the tank sending unit grounded to? Maybe whatever that is, it is not well grounded itself.
     
  7. Sep 17, 2019
    Lee Bennett

    Lee Bennett Banned

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    Mine is grounded through the tub and thus onwards to the frame and eventually to the battery's negative.
     
  8. Sep 17, 2019
    Alan28

    Alan28 Well-Known Member Sponsor 2019 Sponsor

    Ch√Ętillon en...
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    I have the same problem.
    I changed the gauge system in the tank and on the dash. All is new.
    My test from the tank was ok and then, when connected, just a small movement of the tank level needle.
    So I decided to do nothing... I take note of the filling at the station, so I know when to refill.
    I am fed up with these ground connections, there is a bad one somewhere anihilating the job, but it is boring to check all.
    I have put some new turn signals recently, and discovered again that thre was something wrong with the ground, but what... I need to stay below the Jeep, it is unpleasant, and, it can wait...
    My Jeep works so well that this small problem is nothing in comparison with all the joy I have driving it.
     
  9. Sep 17, 2019
    Dale Boyd

    Dale Boyd New Member

    Pekin, Indiana
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    The sending unit I purchased was a 10-70 ohms as per the original. The sender is grounded via a ground terminal on the sender. I ran a wire from the ground terminal to the rear bumper. This was sufficient to make the sender work find outside of the tank. With the arm at the lowest setting, the gauge read empty. With the arm raised to the highest position, the gauge read full. After installing in the tank and handing the tank, only a small movement of the fuel gauge needle when the ignition is turned on, with no movement whether the tank is empty or full.
     
    Last edited by a moderator: Sep 17, 2019
  10. Sep 17, 2019
    zila

    zila I throw poop

    Rock Springs,...
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  11. Sep 17, 2019
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor 2019 Sponsor

    cordele, Ga.
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    As the tank is home made it is possible that when you installed the different (from previous) fuel sender that the new sender float is hitting against an internal baffle and won't raise with the fuel level.
     
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  12. Sep 18, 2019
    Dale Boyd

    Dale Boyd New Member

    Pekin, Indiana
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    That is what I am thinking. Guess I will drive it for a while to run down the gas level, then pull the tank and see if rotating the float will help.
     
  13. Sep 18, 2019
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor 2019 Sponsor

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    If you have the round sender cover with 6 screw holes you will notice they are not equally spaced. The off-set screw spacing was to properly orient the float away from the tank baffle.
     
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  14. Sep 18, 2019
    Dale Boyd

    Dale Boyd New Member

    Pekin, Indiana
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    It has 5 holes, also unevenly spaced, but it is possible to turn the float to different directions. The replacement float I purchased does not look anything like what I took out. I could not find anything that looked like the previous float, so I expect it must have been pretty old.
     
  15. Sep 18, 2019
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor 2019 Sponsor

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    So the VDO sender could be for anything. The jeep senders 5 screw holes were 6 volt and the 6 hole were 12 volt. Yours I have no idea. Sorry.
     
  16. Sep 18, 2019
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Are you sure you got this straight? Or am I confused?

    I have a six hole unit OEM in my '56 F-head, and it absolutely is six volt. Was looking at it today.

    Would a Dauntless in 1971 ever have had six volt option?
     
    Last edited: Sep 18, 2019
  17. Sep 18, 2019
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

    Tantallon, Nova...
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    Never heard of a 6 volt intermediate. :shrug:

    Should not be any difference in the sender between 6 & 12 volt vehicles, the instrument regulator puts out 5 volts on either.
     
  18. Sep 19, 2019
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor 2019 Sponsor

    cordele, Ga.
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    That is true Howard and I was not clear on this as I was referring to the voltage of the vehicle. I still had wrong info as Kaiser Willys says 46-66 is 5 hole sender and 55-66 is 6 hole. Kinda confusing. Guess it depended on what tank you had vice year.
     
  19. Sep 19, 2019
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

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    Yup, but I think his tank came stock under the back floor so all bets are off.
     
  20. Sep 19, 2019
    Dale Boyd

    Dale Boyd New Member

    Pekin, Indiana
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    Yes, the tank on this CJ5 is definately not OE. The PO had removed the original tank and skid plate and welded up a tank out of 1/8" steel plate which bolts directly to the points where the skid plate went originally. The float I purchased was advertised as universal and adjustable, so it seemed to be the best shot at getting something to work. I also considered just reverting back to a standard fuel tank. I can find replacement tanks, but no skid plates. I believe I would need the skid plate to mount an original type fuel tank.
     

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