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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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    thanks Guys - I'll get on it tonight!
     
  2. Dec 5, 2018
    Rick Whitson

    Rick Whitson Detroit Area Sponsor 2019 Sponsor

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    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
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    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...
     
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  4. Jan 12, 2019
    willie2323

    willie2323 Purchased new

    Phoenix, Arizona
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    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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  6. Jan 13, 2019
    willie2323

    willie2323 Purchased new

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    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
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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 Purchased new

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    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
     
  9. Jan 26, 2019
    Magiccoolbus

    Magiccoolbus New Member

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    Been following this thread, as I have similar issues. My solution was not to wire in the 7806. But to use a sealed DC to DC converter, [Amazon for 6.99, the following is the part description to search: "5V 1A 5W DC Converter Regulator DC 12V 24V (8V-40V) Step-Down to DC 5V 1A 5W Waterproof Car Power Supply Module Voltage Converter Regulator Transformer"]. Even though the 7806 is a great solution, it does have heat issues and I wanted to use this converter for other 5v supply later on, ie. USB power. Pardon the mess on the bench-always gets like that during a project.

    I also purposely used the SW Fuel gauge and the aftermarket Temp as I wanted them to swing down from the top. I also used the vinyl gauge faces from whitegauges.net , bear in mind that they have white or the original style black. Their templates are for the original SW gauges which swing opposite of the Omix style. They also have the later CJ style gauge faces, plus 100's more. I have used them for many restorations.

    The early gauges also do not have provisions for turn signals, looking closely you will see the pigtails on the back and the very small LED's on the front face. For new color gels for the brights, amps and oil, I have a lifetime supply-I bought a package of 'theatre stage light color gels,' they come in 10 x 10 sheets. The last picture you can see the bright illuminated with a #57 12v bulb. The amp and oil are equally nice. The paint on the housing is glossy black acrylic urethane and the back is silver cadmium from eastwood.

    VR size.jpg VR location.jpg Speedo Complete.jpg
    Bright Indicator.jpg
     
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  10. Feb 3, 2019
    willie2323

    willie2323 Purchased new

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  11. Feb 3, 2019
    Magiccoolbus

    Magiccoolbus New Member

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    Hey, SW refers to the Stewart Warner original gauge. That is what I am using for fuel, the temp. Is one of the aftermarket ones from crown.
     
  12. Feb 3, 2019
    willie2323

    willie2323 Purchased new

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    oh, okay but a little confused; if you used the original SW fuel gauge I thought it had a 5 or 6 volt regulator within and needs to be sourced by 12 volts. Did you bypass the internal stepper regulator and use your DC to DC converter?
    thanx
     
  13. Feb 3, 2019
    Magiccoolbus

    Magiccoolbus New Member

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    As far as I know, the fuel gauge is a 12 volt unit, fed from a keyed ignition source (I) .the sender feed (S) uses variable resistance from the fuel tank sender to drive the needle. The (A) is the internal voltage regulator 6v output that is hooked to the temp sender (A) with that bar thingy. While my Stewart Warner fuel gauge VR output worked, I wanted a cleaner 5 volts that I could use for some other needs. Hope that helps.
     
  14. Feb 4, 2019
    willie2323

    willie2323 Purchased new

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    oh, okay. I was under the impression both gauges were 5-6 volt and could be damaged when/if the ground was compromised to the cluster. If the fuel gauge is indeed 12 volt I may have mis-diagnosed it to be damaged. I will recheck resistances of my original fuel gauge.

    thanx,
    willie
     
  15. Feb 4, 2019
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

    Tantallon, Nova...
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    That is correct, 12 volts is fed to the regulator internal to the fuel gauge can but both the fuel & temp gauge mechanisms work on the 5 volts output from the regulator.
     
  16. Feb 4, 2019
    willie2323

    willie2323 Purchased new

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    okay, thank you, thought this was the case. One possibility in diagnosing the gauges is what was mentioned above...either the needle is being restricted by physical interference or as in my case, since the gauge has not worked for such a long time the damping grease may be restricting its movement.
    great input all,

    cheers,
    willie
     
  17. Feb 4, 2019
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Measure continuity through the gauge. Huge resistance say 20M to infinite, indicates a broken moving coil. Unlikely you can salvage such a gauge.
     
  18. Feb 4, 2019
    willie2323

    willie2323 Purchased new

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    JeepFuelGauge2.jpg
    Okay, curiosity got the best of me, I opened my fuel gauge as the resistance measurements were not correct AND I wanted to know about the regulator. From the above image I can see indeed the regulator affects both the fuel and the temp gauge as the 12 volt post (upper left in this view) goes immediately to the "stepper" regulator on the left prior to the fuel gauge and then on to the temp gauge via the strap between the two gauges. As well I can see where the tiny wire has broken from the bottom "adhesive" blob. From the resistance measurements that are specified for both fuel and temp gauges (19-21 ohms), I can see they are the same gauges. Since I have two clusters with two failed fuel gauges and apparently good temp gauges that measure correctly (19-21 ohms), I am thinking I will use one good temp gauge as my fuel gauge, just change the cover plate from temp to fuel from the spare cluster...should work. And of course source them both (independently) with 7806 regulators.
     
  19. Feb 4, 2019
    willie2323

    willie2323 Purchased new

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    both gauges work beautifully with the 7806 regulators...10 ohms for full, 25 ohms (I have a 0-25 ohm potentiometer) about 5/8 full...wonderful,
     

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