Fuel Gauge Inop

Fuel and Air Systems

  1. Zak

    Zak Well-Known Member

    Messages:
    53
    Likes Received:
    1
    Joined:
    Jun 3, 2010
    Location:
    Valdosta, Georgia
    Local Time:
    8:10 PM
    Fellow "A" body maintainers,
    Racking my cranium trying to figure out this fuel gauge anomaly. Needle moves ever so slightly to just above the "E". Here's what I've accomplished:
    - Installed new tank/sending unit and got that slight movement above "E"
    -grounded power lead at tank and gauge will peg out to full and return to empty. That tells me wiring up thru the instrument cluster is good.
    -Removed sending unit. Rheostat ohmed good from empty to full. 3ohms to 84 ohms
    -With unit out of tank and grounded I manually moved float and gauge read empty to full.
    -Re-installed sender and grounded as per Mopar and with half tank fuel had no response to gauge movement.
    -tried all different variations placing ground in different locations. All continuity checks were good.
    -Ensured I had my engine to firewall ground intact.
    -Ensured cluster was grounded to dash.
    - Manipulated ignition switch to see if any help but none.
    -Tried a second sending unit....same result
    -Just for giggles, I replaced the volt limiter on cluster...same result.
    -I turned the sender upside down in the tank and it read full on gauge. Re-installed it right side up and no reading.
    - Could it be a baffle in the tank is installed incorrectly? Need you guys to help me right the ship.
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

    Messages:
    44,973
    Likes Received:
    12554
    Joined:
    Oct 14, 2010
    Location:
    Idaho
    Local Time:
    5:10 PM
    You need to treat the gauges as a SYSTEM. Do the other gauges work? If so, you can "sort of temporarily" eliminate some of the system

    You evidently have a second sender that is out of a tank? If so you can use that as your test device.............

    The photo below is a third party gauge tester that mimicks the factory one depicted in the service manual. If you do NOT have a service manual you need to wander over to MyMopar and download one.......free

    c-3826-jpg-jpg.jpg

    Notice the yellow resistance readings. Someone created this edited photo, thank you whoever that was!!! Anyhow notice the 3 readings. you can take your gas sender and use your ohmeter to adjust it to either the middle or high reading, then hook it to the temp gauge wire, turn on the key, and verify that the temp gauge goes to that reading. This proves the "rest of" the system works (the IVR, etc) and that your concept is sound.

    If this happens, connect your test device.......adjusted for the same as above......to the fuel sender wire. It should drive the gauge to same reading

    ==================================================

    If the above test "passes" then it must be something to do with the sender in the tank. Start by measuring the sender resistance as installed in the tank, putting your probes onto the SENDER flange and the sender wire terminal. If you have the proper "empty" reading, then of course connecting to the gauge should indicate that

    IF NOT, now leave the key 'in run' and stab your probe onto a GOOD body ground, making sure to stab through rust, etc. Now stab the remaining probe onto the sender flange. ANY voltage there means it is not truly grounded.

    Next to confirm, pull the sender wire off. Perform same test with resistance. Meter should show zero or very close to zero.
    =========================================================
    When you reduce all the BS this is a fairly simple circuit. The functional path is:

    Ignition switch........to PC board harness connector...........to IVR.........to gauge.........through gauge...........to harness connector.............sender wire down to left kick panel rear harness connector...........out to rear of car........to sender connector........through sender.......to ground

    =============================================================

    Common problems are loose pins on the PC board connector not making connection to pc board traces, bad connection at the IVR contacts to the board traces, and poor connections from the board traces to the gauge stud/ nuts. Gauge can be bad. Kick panel connector can be loose/ corroded, and SENDER END CONNECTOR can be damaged/ corroded inside the boot.

    Sender can be poorly grounded. I would "do what it takes" to get a pigtail connected to the sender-------even if you solder one to say, the fuel nipple down low,.......and bolt the pigtail to a 'clean' point on the body
     
    Last edited by a moderator: Sep 26, 2020
    • Like Like x 1
    • Dana67Dart

      Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

      Messages:
      5,125
      Likes Received:
      3161
      Joined:
      Jul 16, 2017
      Location:
      Northern Colorado
      Local Time:
      6:10 PM
      If the tank is a replacement that is supposed to be an OEM style there should not be any baffels.

      With the sender removed you should be able to see inside to verify.

      You mentioned that you were able to put the sender in upside down. Not sure it should be able to do that.

      Would you post a part number and a photo of your senders

      From what you wrote in the first post you have checked everything I would have done.

      The fact that 2 senders are doing the same thing said it is not the sender.

      That you can ground the sender wire and the gauge moves / pegs says your guages and ivr are functioning.

      Warning: grounding your sender wire for more than a second or two can burn out your guage.

      Some things that come to mind is if there is a broken wire in the sender wire that you connect to the sender. It could be that in the natural position the wire is not making connection. In any other position it is making connection.
       
    • Zak

      Zak Well-Known Member

      Messages:
      53
      Likes Received:
      1
      Joined:
      Jun 3, 2010
      Location:
      Valdosta, Georgia
      Local Time:
      8:10 PM
      Dana,
      Definitely appreciate the input with regards to rechecking resistance methods. I was remiss in stating initial post that all other gauges were operational and that I had the cluster circuit board out and verified pin security. Point taken as to " should be no baffles" in tank. That was my thought process after I placed the sender in upside down but obviously couldn't secure it and it gauge read. I'll recheck power lead to sender also. Appreciate your detailed response...John
       
    • halifaxhops

      halifaxhops It's going to get stupid around here! FABO Gold Member

      Messages:
      60,814
      Likes Received:
      29355
      Joined:
      Jan 20, 2014
      Location:
      CENTRURAL, PA
      Local Time:
      8:10 PM
      A big one is the ground strap to the fuel line to sending unit. Fast check with a ohm meter from the surface of the sending unit to ground.
       
      • Agree Agree x 2
      • RedFish

        RedFish Well-Known Member

        Messages:
        24,507
        Likes Received:
        3039
        Joined:
        Sep 5, 2007
        Local Time:
        7:10 PM
        The most common cause of condition you describe is fuel inside the float. 2 senders doing same thing is probably 2 different floats so thats not the problem.
        Here's additional thought... to pull these senders requires tank be drained below half tank. Many owners who install the aftermarkets sender do get a full reading on their gauge when they fill it up. Later down the road when the gauge reads near empty, only 7 to 9 gallons are required to fill it. So... they install a meter match unit to make their gauge read correctly with the incorrect sender. So I guess my question is have you filled the tank?
        I didn't see year model but I'll bet its a late model with the 13 ohm fuel gauge. The earlier 20 ohm fuel gauges seem to work better with aftermarket senders.
         
        • Like Like x 1
        • AAndrews

          AAndrews Supercuda

          Messages:
          572
          Likes Received:
          484
          Joined:
          Nov 5, 2014
          Location:
          St. John's, Newfoundland, Canada
          Local Time:
          9:40 PM

          Here's one you may not have checked..

          Did you check to see if the gauge needle is being interfered with as it is trying to deflect to the right?

          If you had the cluster apart , when you reassembled it, you may have inadvertently squat the plastic housing or the metal graduation plate into the pointer and stopped it from moving.

          I had exactly this happen with my temp gauge and only found it when in desperation, I completely disassembled the cluster.

          Its always something simple that causes strange problems like this. Unfortunately, they are only simple after you find the solution!!!

          Hope this helps...
           
          Last edited: Sep 26, 2020
        • Dana67Dart

          Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

          Messages:
          5,125
          Likes Received:
          3161
          Joined:
          Jul 16, 2017
          Location:
          Northern Colorado
          Local Time:
          6:10 PM
          Zac, are these assumptions correct when you did your testing

          1. The guages cluster is OEM
          2. The guage cluster is installed into the car
          3. The wiring is OEM
          As others have stated, if some of the tests were performed with the cluster out and tested good, there could be an issue once it is reinstalled.

          Red fish brings up an interesting point about filling the tank.

          In this post at the end I have a plot.
          Product Review: A100 Fuel Sender For 67 Dart
          I have verious senders in the tank in my dart. And I plot sender resistance after draining the tank and adding 1 gallon at a time back to the tank. Your sender should have reading similar.

          Lastly please post photos of your sender and the manufacturer and part number.
           
        • CRUZE 418

          CRUZE 418 FABO Gold Member FABO Gold Member

          Messages:
          273
          Likes Received:
          89
          Joined:
          Mar 11, 2019
          Location:
          Illinois
          Local Time:
          7:10 PM
          This has been discussed so many times.
          Aftermarket fuel sending units, unless you are willing to do the meter match thing, the new sending units are junk. I thought that I had a bad one and bought another, that's when I found out. Got an original, had it restored and wow, it works just like it supposed to.
           
        • Dana67Dart

          Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

          Messages:
          5,125
          Likes Received:
          3161
          Joined:
          Jul 16, 2017
          Location:
          Northern Colorado
          Local Time:
          6:10 PM
          Agreed
          also agreed, BUT OP has a unique situation and he has done a lot of testing to find the cause.

          Not saying it is not his sender ( range issue) but he tried 2 with the same result (don't know if they are the same manufacturer)
           
        • CRUZE 418

          CRUZE 418 FABO Gold Member FABO Gold Member

          Messages:
          273
          Likes Received:
          89
          Joined:
          Mar 11, 2019
          Location:
          Illinois
          Local Time:
          7:10 PM
          My two new ones were probably or not, made at the same place. One was in when I got the car, then I bought a real expensive one. Same result.
          Hope you get it figured out!
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
          Thanks Red..........she's a 71 Duster 318 regular dash
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
          Dana,
          Yes to all three. Will see what it does when I fill tank. She's half full. Purchased the tank and sender off ebay. I'll see what the p/n manufacturer is...thanks
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
          Cruze,
          That's interesting and I may do the same
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
          Dana,
          Purchased sender off ebay for $27. P/N: 38611578....no manufacturer imprint....
           
        • Dana67Dart

          Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

          Messages:
          5,125
          Likes Received:
          3161
          Joined:
          Jul 16, 2017
          Location:
          Northern Colorado
          Local Time:
          6:10 PM
          Looks like the typical aftermarket sender.

          Something else you can do is get a resistance measurement from sender output to ground as it is now.

          How do you know you have 1/2 tank?

          Lastly watch for leaks at the sender when you do fill it. I found that the replacement gasket was not as thick as the OEM and it leaked. I ended up using 2 gaskets.
           
          Last edited: Sep 27, 2020
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
          Red,
          I appreciate your experience. Filled it up and ...bam....went to full.....my thoughts now are the float arm didn't make contact with the rheostat board until tank loaded up. returning sender...thanks for the tip...John
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
           
        • Zak

          Zak Well-Known Member

          Messages:
          53
          Likes Received:
          1
          Joined:
          Jun 3, 2010
          Location:
          Valdosta, Georgia
          Local Time:
          8:10 PM
          Dana,
          Red's input to fill tank all the way to full panned out. Gauge shot right up to full. My thoughts are float arm wobbly preventing rheostat board providing signal to system when fuel level below full. thanks for your expertise. Returning this sender.. Spectre a good one to aquire?
           
        • CRUZE 418

          CRUZE 418 FABO Gold Member FABO Gold Member

          Messages:
          273
          Likes Received:
          89
          Joined:
          Mar 11, 2019
          Location:
          Illinois
          Local Time:
          7:10 PM
          I personally would like to know if your gauge reads properly now and after you have gone through a tank or two of gas. I am a doubting Thomas. I also do not want to give out bad info on the current supply of sending units available.
          I do not do electrical well and would have trouble trying to sort through symbols on a meter. I never checked any resistance in my system. I went on the advice of the supplier of my new circuit board, that none of the new senders were compatible. Maybe something has changed.
          Good luck!
           
        • RedFish

          RedFish Well-Known Member

          Messages:
          24,507
          Likes Received:
          3039
          Joined:
          Sep 5, 2007
          Local Time:
          7:10 PM
          80 ohms or greater = no needle movement. 73 ohms takes the needle away from home and up to the first hash mark. There is no low fuel warning lamp but the empty hash mark and 73 ohms says you have about 3 gallons in there.
          You stated your needle would leave home at switch on, so there was connection/ohm signal from the sender(s), just a wrong signal. You gauge needs 35 ohms at 1/4 tank, 23 ohms at 1/2 tank, 14 ohms at 3/4 tank, 10 ohms at full. There is nothing linear about those numbers. Calculator says a linear sender sends about 45 ohms at half tank. That 45 ohms is around 1/8 tank on your gauge. Install the meter match unit to adjust the ohms signal from a linear sender to match your meter/gauge.
           
        1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
          By continuing to use this site, you are consenting to our use of cookies.