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Adjusting Fuel Gauge

Discussion in 'Early CJ5 and CJ6 Tech' started by mickeykelley, Dec 26, 2021.

  1. Dec 26, 2021
    mickeykelley

    mickeykelley Well-Known Member

    Republic of Texas
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    The fuel gauge works fine except that it reads wrong. Recently it was at the E , but when I went top fill it with non-ethanol gas before taking him to the mountains, it only took 5 gals. I’ve noticed this before that it drops from full fairly quick and goes below empty for ever. Is it possible to bend the float arm to adjust this?
     
  2. Dec 26, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    I'd suppose so.

    Not an expert here, but first I'd check every electrical connection in the circuit to eliminate any possible resistance and ensure true gauge values. Including grounds. Might also check that the instrument cluster voltage regulator is calibrated correctly.
     
    Last edited: Dec 26, 2021
  3. Dec 26, 2021
    wheelie

    wheelie beeg dummy 2021 Sponsor

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    Mine had tabs that limited travel of the float arm in either direction.
     
  4. Dec 26, 2021
    Steve's 70-5

    Steve's 70-5 Active Member 2020 Sponsor

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    You will have to bend the wire the float is on. Adjust float height when empty and full, which means pull sending unit.
     
  5. Dec 28, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Yes.

    Pull the sender and measure the depth of the tank. Adjust the float arm so that you reach the stop on the sender and the depth you want at the same time. The sender should ohm-out when empty at the spec gioven in your FSM. Adjust the top stop so the arm is all the way up and not touching the bottom of the tank.

    Shake the float to make sure it's not partially flooded.

    Note this is not a precision instrument. Likely you can make it better by adjusting. You can also test that you get a full-half-empty reading at the proper position of the float.
     
  6. Dec 28, 2021
    hooliganrick

    hooliganrick Sponsor

    San Diego, CA
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    i have the same issue. I call it the "60 mile tank". It would sit at full for 60 miles or so, then drop like a rock until it hit "E", then it would only take about 6 or 7 gals to fill. So i adjusted the bend in the float and tabs. So now it still sits at full for miles, but i have a more accurate indication when it gets to "E". Gives me about a 2 gal reserve. I always write down my mileage at fillup as a backup. What i did for adjusting was to get the tank down to a couple of gallons, then bend the float arm to where i wanted it to read on the gauge. I would make an adjustment, then hold it flat in it's position, and re-adjust it to where I wanted.....no need to screw it down each time. Make sure you keep the grounding wire attached.
     
  7. Dec 28, 2021
    mickeykelley

    mickeykelley Well-Known Member

    Republic of Texas
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    My main things is the E being closer. I replaced the float back in 2015 because it was liquid logged and it looked like bending was an option. But I was curious if others had done that or if there was another method. So as run this tank down, I’ll get it close then drain it totally and measure exactly 2 gallons, put it in and then adjust the float. Thanks for input.
     
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  8. Dec 28, 2021
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

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    Has it always been like this?

    Check the resistance readings for the sender- something is wrong & bending the sender arm would just be a band aid.
     
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  9. Dec 28, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    x2
     
  10. Dec 30, 2021
    mickeykelley

    mickeykelley Well-Known Member

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    Yes but I could use a high quality bandaid. :waiting: So I’m guessing get a reading at full then run to empty and read?
     
  11. Dec 30, 2021
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

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    You can pull the sender, this will take less time than running through a tank of gas :)
     
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  12. Dec 30, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Or just siphon it. Even less time.
     
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  13. Dec 30, 2021
    hooliganrick

    hooliganrick Sponsor

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    It will still boil down to adjusting the float arm if you want to adjust for "E". I'm sure these units are adjusted for "in the ballpark" from the factory. All you'll be doing is fine tuning it for your vehicle. No harm, no foul......
     
  14. Dec 30, 2021
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

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    Not necessarily- if the sender or the gauge itself are defective all the arm bending in the world may not get the thing to read correctly.
     
  15. Dec 31, 2021
    hooliganrick

    hooliganrick Sponsor

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    I know from my personal experience that adjusting the float arm does work for setting the "empty" point on the gauge. Just as the OP stated...mine was/is the same way. That's how my current system works. I've done the resistance readings, and I've also made sure that the gauges(2) and senders(3) were compatible. So...although I don't get any needle movement until I've gone 60-70 miles, I at least have my gauge calibrated so when it hits "E", I know I have roughly 2 gals left. I know how much fuel I have when I start.....I want to know how much I have close to empty. Remember, we're working with primitive instruments here....LOL.
     
  16. Dec 31, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    They worked okay in 1955. Perhaps I'd use the word "simple."

    If the range can only be accurate at one extreme, and the electrical aspects are correct, my guess is that a generic float arm is not the right length for the Jeep tank.

    In other words the radius of the quadrant it describes does not match the height of the tank. I would try to correct the "length" of the arm to allow its full swing, not just bending it to coincide with "empty."
     
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  17. Dec 31, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    I can attest to OEM working properly. At least back in the day it did. The stock '59 CJ5 I had in '67 was extremely accurate all the way from full to empty. I could drive and trust the gas gauge and wait until it had less than a gallon in the tank. That was when 50 cents worth of gas was good for close to 2 gallons.
     
    Last edited: Dec 31, 2021
  18. Dec 31, 2021
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
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    :shock:
     
  19. Dec 31, 2021
    jpflat2a

    jpflat2a what's that noise?

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    If I recall the trick to bending the float arm is the opposite of the direction you want to go.
    Up is down and down is up....or something similar.
     
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  20. Dec 31, 2021
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

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    You can't get the gauge to read empty only when it actually is empty, the float doesn't ride right on the top of the gas, IIRC it's submerged about halfway into the fuel so even when it's resting on the bottom there can be an inch or so of fuel in there.

    Same deal with "full". There's not actually a lot of arm movement in there between full & empty. If the sender is out of whack or the gauge movement is not properly set bending the arm will get the right reading in one spot and completely out to lunch in all others. :(
     
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