Fuel Gauge Question

Mopar Interiors

  1. Dan_the_Mopar_Man

    Dan_the_Mopar_Man Member

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    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

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    And there is no change in the oil pressure gauge ?
     
  3. Yote

    Yote Well-Known Member

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    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
     
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    • Hellrats

      Hellrats Still wrenching after all these years FABO Gold Member

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      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.
       
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      • cannucky

        cannucky The Guy With No Birthday

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        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

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        • 67Dart273

          67Dart273 Well-Known Member

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          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

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        • jed

          jed Active Member

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          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

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          • famous bob

            famous bob mopar misfit

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            ---------------$105-----------
             
          • Mr.FT

            Mr.FT FABO Gold Member FABO Gold Member

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            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.
             
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            • toolmanmike

              toolmanmike FABO Staff Staff Member FABO Gold Member

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              Stock gauge?
               
            • Mr.FT

              Mr.FT FABO Gold Member FABO Gold Member

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              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

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              Meter Match unit ordered....I'll chime in with my results after installing.

              Jeff
               
            • Mr.FT

              Mr.FT FABO Gold Member FABO Gold Member

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              I hope you have as good of luck as I did.
               
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              • MrJLR

                MrJLR Built, not bought FABO Gold Member

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                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

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                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
                 
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