1970 road runner Fuel Gauge issues

Lucky Lar · Nov 11, 2017

Can’t get fuel gauge to read full when the tank is full of gas

I have 2 sending units, one brand new the other looks original, when I hook them up out of the tank the sending units & the gauge in the car work perfect

But when I put them back in the tank they will only go to a little under ¾ when the tank is full

Has anybody had the same issue, and is there a fix

Thanks larry

PurpleBeeper · Nov 11, 2017

I'm dealing with a similar issue, but mine do the same thing out of the car too, so I suspect my gage itself. For you, I think you only have a couple possibilities. 1. Less than ideal, but so-so, ground when installed. Maybe try an extra ground wire to the sending unit. 2. Something is keeping the float from going up all the way. My guesses would be wrong sender, wrong tank, arm on float bent causing it to hit top of tank, car jacked up in rear end or front end causing an odd tank angle, rear end low so you can't actually fill tank completely (or would run out filler) so the gas station pump shuts off when the tank is only 3/4 full...something along those lines

65-440 · Nov 12, 2017

My aftermarket sender does the same thing. You need to figure out the distance on the inside of the tank from top to bottom where the float sits. Then need to tweak the arm so full and empty (using an ohm meter) match that distance. I just deal with mine, until I can find a sender that needs no tweaking ! Fortunately I can look into the tank through the filler neck and get an idea of how far I can go before I need gas !

Lucky Lar · Nov 12, 2017

PurpleBeeper said:
I'm dealing with a similar issue, but mine do the same thing out of the car too, so I suspect my gage itself. For you, I think you only have a couple possibilities. 1. Less than ideal, but so-so, ground when installed. Maybe try an extra ground wire to the sending unit. 2. Something is keeping the float from going up all the way. My guesses would be wrong sender, wrong tank, arm on float bent causing it to hit top of tank, car jacked up in rear end or front end causing an odd tank angle, rear end low so you can't actually fill tank completely (or would run out filler) so the gas station pump shuts off when the tank is only 3/4 full...something along those lines

thanks

Lucky Lar · Nov 12, 2017

65-440 said:
My aftermarket sender does the same thing. You need to figure out the distance on the inside of the tank from top to bottom where the float sits. Then need to tweak the arm so full and empty (using an ohm meter) match that distance. I just deal with mine, until I can find a sender that needs no tweaking ! Fortunately I can look into the tank through the filler neck and get an idea of how far I can go before I need gas !

Thanks

Lucky Lar · Jan 30, 2018

Finally was able to get the fuel gauge to read full with a full tank
Installed Bill Rolik sending unit, i could see that the neck on the BR unit sits lower in the tank than the one I pulled out & the first after market unit i bought
the other 2 units floats would hit the top of the tank in the 3/4 position

65-440 · Jan 31, 2018

Lucky Lar said:
Finally was able to get the fuel gauge to read full with a full tank
Installed Bill Rolik sending unit, i could see that the neck on the BR unit sits lower in the tank than the one I pulled out & the first after market unit i bought
the other 2 units floats would hit the top of the tank in the 3/4 position

That's awesome news, I was looking into his stuff. Have heard nothing but good ... thanks for the update !

1970 road runner Fuel Gauge issues

Lucky Lar

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PurpleBeeper

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65-440

Well-Known Member

Lucky Lar

Well-Known Member

Lucky Lar

Well-Known Member

Lucky Lar

Well-Known Member

65-440

Well-Known Member

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