Fuel Gauge Question

Discussion in 'Mopar Interiors' started by Dan_the_Mopar_Man, May 27, 2018.

  1. Dan_the_Mopar_Man

    Dan_the_Mopar_Man Member

    Messages:
    5
    Likes Received:
    0
    Joined:
    Apr 17, 2018
    Location:
    Central New York
    Local Time:
    9:58 PM
    Gotta question regarding my 1974 Duster fuel gauge. It's not reading accurately, when I fill the tank it goes over to full, but after driving 30 miles it's already on half, I know I'm not burning that much gas, plus when I go to refill it at half, it barely takes anything to fill it again, so it's moving over to half way too soon. Any ideas?

    Dan
     
  2. Murray

    Murray FABO Gold Member FABO Gold Member

    Messages:
    484
    Likes Received:
    185
    Joined:
    Apr 19, 2010
    Location:
    San Jose, California
    Local Time:
    6:58 PM
    And there is no change in the oil pressure gauge ?
     
  3. Yote

    Yote Well-Known Member

    Messages:
    1,167
    Likes Received:
    473
    Joined:
    Aug 30, 2015
    Location:
    far eastern Colorado
    Local Time:
    7:58 PM
    My '72 Demon gauge operates in a similar fashion. Maybe not to 1/2 in 30 miles, but the first 1/2 seems to drop pretty quickly. The bottom 1/2 takes a lot longer. My sending unit is an origional from a Duster '73 or newer, not sure of exact year. If you are thinking of replacing the sending unit the new replacements are much worse.
    Yote
     
    • Agree Agree x 1
    • Hellrats

      Hellrats Still wrenching after all these years

      Messages:
      531
      Likes Received:
      295
      Joined:
      Jan 24, 2012
      Location:
      Hartville, Ohio
      Local Time:
      9:58 PM
      If it's an aftermarket fuel tank sending unit none of them read correctly. Do a search on here there is lots of information on ways to fix it.
       
      • Agree Agree x 1
      • cannucky

        cannucky The Guy With No Birthday

        Messages:
        5,570
        Likes Received:
        541
        Joined:
        Sep 25, 2008
        Location:
        Victoria BC
        View My Photos
        Local Time:
        6:58 PM
        If it's a stock ralleye gauge that internal voltage regulator can do some weird things to your gauges , had 1 where the temp and oil pressure gauges would climb as the fuel was consumed , both read correctly with a full tank but each in turn would climb to max as the fuel went down , both maxed out after burning about 2 thirds of the tank LOL .
         
      • Mr.FT

        Mr.FT FABO Gold Member FABO Gold Member

        Messages:
        854
        Likes Received:
        30
        Joined:
        Feb 14, 2011
        Location:
        New Jersey
        Local Time:
        9:58 PM
        • Thanks! Thanks! x 1
        • 67Dart273

          67Dart273 Well-Known Member

          Messages:
          37,365
          Likes Received:
          5115
          Joined:
          Oct 14, 2010
          Location:
          Idaho
          View My Photos
          Local Time:
          6:58 PM
          Do a site search. "We" have posted hundreds of posts about this.

          The gauge unit may be out of cal
          The instrument voltage limiter by any other name may be "off"
          The sender especially if it's a "repop" is a large problem

          The factory gauge tester (read your service manual) was a switchbox with 3 resistors, to simulate the senders at low/ empty, mid scale/ 1/2 and high/ full. Here is one version. Someone kindly added the resistances to the photo:

          c-3826-jpg.jpg

          ...........so you can also do that "backwards." These test boxes were meant to be put from the sender wire to ground, but you can ALSO "let's say" you know you have 1/2 a tank of actual fuel. "Let's say" you know this because you drained it, filled it and measured it, and then ended up with 1/2 that "measured."

          This means the sender when unplugged, and measured with an ohmeter, should read somewhere around 20-25 ohms

          If it does, and the gauge doesn't read that, then the gauge/ cluster connections/ IVR is some-ting-wong.

          Also notice from the tester resistances that THESE GAUGES ARE NOT linear!!! In other words, twice as much sender resistance doesn't change it from MT to 1/2, and twice that much does not result in "full"
           
        • 67Dart273

          67Dart273 Well-Known Member

          Messages:
          37,365
          Likes Received:
          5115
          Joined:
          Oct 14, 2010
          Location:
          Idaho
          View My Photos
          Local Time:
          6:58 PM
        • jed

          jed Active Member

          Messages:
          35
          Likes Received:
          15
          Joined:
          Apr 12, 2009
          Local Time:
          8:58 PM
          My stock pickup in my 72 Duster was doing same thing, pulled it out float looked perfect but it was half filled with gasoline. Put new float in, works perfectly now. -Jed.
           
        • toolmanmike

          toolmanmike FABO Staff Staff Member FABO Gold Member

          Messages:
          30,066
          Likes Received:
          12072
          Joined:
          Jan 18, 2006
          Location:
          Iowa
          View My Photos
          Local Time:
          8:58 PM
           
          • Like Like x 1
          • famous bob

            famous bob mopar misfit

            Messages:
            9,937
            Likes Received:
            2193
            Joined:
            Aug 14, 2011
            Location:
            okla
            Local Time:
            8:58 PM
            ---------------$105-----------
             
          • Mr.FT

            Mr.FT FABO Gold Member FABO Gold Member

            Messages:
            854
            Likes Received:
            30
            Joined:
            Feb 14, 2011
            Location:
            New Jersey
            Local Time:
            9:58 PM
            I've been using the Meter Match mentioned above for @ 2 years now. I've had zero issues with it in my 72 Demon 340.
             
            • Thanks! Thanks! x 1
            • toolmanmike

              toolmanmike FABO Staff Staff Member FABO Gold Member

              Messages:
              30,066
              Likes Received:
              12072
              Joined:
              Jan 18, 2006
              Location:
              Iowa
              View My Photos
              Local Time:
              8:58 PM
              Stock gauge?
               
            • Mr.FT

              Mr.FT FABO Gold Member FABO Gold Member

              Messages:
              854
              Likes Received:
              30
              Joined:
              Feb 14, 2011
              Location:
              New Jersey
              Local Time:
              9:58 PM
              Yes stock gauge and replacement sender. The sender was a direct replacement from Jegs if I remember correctly. It would read full when I filled the tank but when on empty it would only take @ 8 gal to full. That is why I installed the meter match and all good now.
               
            • MrJLR

              MrJLR Built, not bought FABO Gold Member

              Messages:
              3,836
              Likes Received:
              2264
              Joined:
              May 14, 2015
              Location:
              Chino, California
              View My Photos
              Local Time:
              6:58 PM
              Meter Match unit ordered....I'll chime in with my results after installing.

              Jeff
               
            • Mr.FT

              Mr.FT FABO Gold Member FABO Gold Member

              Messages:
              854
              Likes Received:
              30
              Joined:
              Feb 14, 2011
              Location:
              New Jersey
              Local Time:
              9:58 PM
              I hope you have as good of luck as I did.
               
              • Thanks! Thanks! x 1
              • MrJLR

                MrJLR Built, not bought FABO Gold Member

                Messages:
                3,836
                Likes Received:
                2264
                Joined:
                May 14, 2015
                Location:
                Chino, California
                View My Photos
                Local Time:
                6:58 PM
                My MeterMatch unit arrived today.

                image000001.jpg

                Looks simple enough....I'll try to install it this weekend and I'll report back!

                Jeff
                 
              • moparmandan

                moparmandan FABO Gold Member FABO Gold Member

                Messages:
                819
                Likes Received:
                393
                Joined:
                Jun 28, 2017
                Location:
                Central FL
                View My Photos
                Local Time:
                9:58 PM
                If you have to have to have the factory look, like everyone says, meter match. If you don't care put a matched aftermarket gauge under the dash. Under the dash was easier. I was mounting gauges there anyway. Reads perfectly.
                20180821_195203.jpg
                 
                • Like Like x 1