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Fuel Gauge issues

Discussion in 'Engine and Drivetrain/Mechanical' started by JonnybravoM3, Jan 13, 2018.

  1. JonnybravoM3

    JonnybravoM3 Member

    Hi all

    Not sure if this is the right place for this query but my fuel gauge on my 65 seems to be inaccurate. After a full fill, it only reads 3/4.

    Was watching videos online and reading over forums and it seems likely that i would need to replace the fuel sending unit. Checked on pony parts and found a 3/8" and 5/16". Would either go on the car?

    Alternately, (i guess?) I could invest in that fuel interface Fuellink which should resolve the problem?

    Any advice appreciated. Thanks!


    Sent from my HTC U11 using Tapatalk
  2. B67FSTB

    B67FSTB The NorCal dude from Belgium

    Thats a common problem but for me it isn't an issue if it reads 3/4 with a full tank.
    Its important that it shows when the tank is almost empty !!:rolleyes:
    Nevertheless , when replacing the sender , you should calibrate it before mounting by tweaking its rod.I think you have the 5/16 line sender.
    This topic has been discussed here at SF a few years back by CMAYNA I think.
    Maybe someone can give the link .
    Last edited: Jan 13, 2018
  3. Horseplay

    Horseplay I Don't Care. Do you?

    Yep, Bruno hits it square on the head. It's a pretty lengthy (and messy) process to swap out the sending unit. You need to drain the tank, etc. The sender works by varying the resistance (measured in ohms) as the float arm rises or lowers. This in turn signals the gauge to move. Start by making sure you have a good connection at the tank. You likely do as it seems the sending unit is not quite adjusted right. By that I mean the arm bent/positioned to move fully from max fill to empty.

    Honestly, if it seems to read accurate from 3/4 down to empty I would leave it for now and just enjoy the car for a while. You will get to know pretty quickly how much gas you have at any point so no real concerns of running empty. Besides, with these cars and carbs you're best to always keep at least 1/4 anyway to avoid siphoning crap up out of the tank.
  4. Midlife

    Midlife Well-Known Member Staff Member Moderator

    The other issue is that the float itself may have a leak, letting gas in so it won't raise all the way up. Something to check.
  5. B67FSTB

    B67FSTB The NorCal dude from Belgium

    wise words here.
  6. 3175375

    3175375 Well-Known Member

    good call, Randy. Replacement senders use plastic floats. When I replaced mine, I transferred the brass float into the replacement sender.
  7. Midlife

    Midlife Well-Known Member Staff Member Moderator

    :D I'm a stable genius!
  8. Mach1 Driver

    Mach1 Driver Active Member

    def: gifted in the construction of a building in which horses are kept, fed, and cared for.
    Midlife likes this.
  9. Patrick Stapler

    Patrick Stapler Active Member

    You're not going to find a accurate repro sending unit. They no longer exist. Reason being, all repros use a linear pot instead of non-linear pot (like the originals) to measure the resistance based on the float level. Well the fuel tank is not a linear shape. Dan Nolan of the Mustang Barn used to have a offshore supplier that reproduced the non-linear versions. Unfortunately for all of us, they didn't sell enough to be worthwhile. I tried last year to get a order up on VMF. Dan agreed to pursuit the possibility, but couldn't get his original supplier to sign up for the task. Supposedly, NPD sells a as close to accurate as you are going to get...yet it is still not a non-linear unit.
  10. bartl

    bartl Old Fart

    I often wonder why the replacement sending unit can't be designed to use a linear pot, but connect it in such a way that the float movement is NOT linear.

    Attached Files:

  11. Midlife

    Midlife Well-Known Member Staff Member Moderator

    The reason is that the sending unit resistance is reversed: low gauge reading is high resistance and high gauge reading is low resistance. It is very hard to make a linear reverse resistor.

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