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Fuel Gauge Question

Discussion in 'Early CJ-5 and CJ-6 Tech' started by tcfeet, Sep 8, 2017.

  1. Dec 4, 2018
    TonyM

    TonyM New Member

    Middle Tennessee
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    Jul 30, 2017
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    34
    thanks Guys - I'll get on it tonight!
     
  2. Dec 5, 2018
    Rick Whitson

    Rick Whitson Detroit Area Sponsor

    I live South of...
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    Dec 2, 2014
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    822
    Did you put a ground wire from one of the screws holding the sender in the tank to ground? That way you know the the sender is grounded for sure. Just something to consider, Good luck
     
  3. Dec 15, 2018
    TonyM

    TonyM New Member

    Middle Tennessee
    Joined:
    Jul 30, 2017
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    34
    Update: I was finally able to get to work on the jeep today and got the fuel gage/fuel sender situation sorted out. Pulled the sender, grounded it outside of the tank, moved the float manually and the gage responded accordingly. Put the sender back in the tank and re-grounded from one of the sender screws, making sure that I had really good contact at the sender screw and things seemed to work. Drove to a nearby hill and put the jeep at various angles to make the float move and the gage responded as it should. Now, I'm not sure how accurate it really is so I'll start checking with a flashlight and/or "the gas stick" once I start to get under 1/2 tank just in case :) Thanks for the ideas and assistance. Now, on to the temp gage and sender...
     
    Beach66Bum and Bowbender like this.
  4. Jan 12, 2019
    willie2323

    willie2323 One Owner

    Phoenix, Arizona
    Joined:
    Dec 10, 2009
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    8
    So if I understand you correctly, both gauges operate off the 5 volt regulator. In other words, the factory regulator in the fuel gauge is the supply voltage for both the fuel and temp gauges?
     
  5. Jan 12, 2019
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Aug 10, 2003
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    19,231
  6. Jan 13, 2019
    willie2323

    willie2323 One Owner

    Phoenix, Arizona
    Joined:
    Dec 10, 2009
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    8
    ahh, so to bypass the VR in the fuel gauge we just need to attach the output of the 5V Reg (once established in the vehicle) to the strap between the fuel and temp gauge and insure a good ground to the cluster housing...correct? I am assuming the sender/ground at the sender and associated wiring are working correctly which in my case they are. Actually we dont even care about a good ground to the cluster at this point, we just need to know the ground on the new 5 volt source is the same ground at the sending unit to complete the circuit, correct?
     
  7. Jan 13, 2019
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
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    The ground on the cluster is important to the VR. With a 7805 or 7806, lose the ground and the VR goes open, and you have no reading. Lose the ground with the original vibrator (PWM VR), and the output goes to constant full voltage, destroying the gauges.

    I'm not sure about the specifics of the CJ cluster - I've only done the 7805 on the J-truck. However, it is correct that you disconnect the regulator in the gauge and substitute the IC regulated voltage. Pretty sure it's the strap that sends 5V to the other gauge. You need to remove the 12V input connection to the gauge, and let that gauge get its 5V connection through what would normally be the 5V outlet from the regulator. If that's not clear, I'll look at it again in the morning.
     
    Last edited: Jan 13, 2019
  8. Jan 14, 2019
    willie2323

    willie2323 One Owner

    Phoenix, Arizona
    Joined:
    Dec 10, 2009
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    8
    It is clear. I was planning to mount the 7806 (I have a few of these) external to the fuel gauge and provide an external-solid ground for the 7806 thereby eliminating the need for the cluster ground, then simply provide that 6V input to the strap between the gauges and let the fuel wiring/tank sensor/and sensor ground complete the circuit which is why it is important to have the 7806 ground and the sensor ground back at the tank, common. eh, several ways to complete the circuit for fuel.
    thanx for the input and good input as well on the dangers of electric fuel pumps :)
    willie
     

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