Gas Gauge Calibration

[Joe Dufresne]

Replaced the rusty gas tank and fuel pick up/float in my '73 Mach 1 a couple of months ago. The gas gauge works, but is very inaccurate. Full goes about a quarter beyond, then when you burn about 4 gallons drops to 1/2 tank. When it is reading empty, I learned through filling it that it only took about 12-13 gallons. Given that it is a 19 gallon tank, something is off. Can the rod that holds the float be bent or adjusted to get closer to what is in the tank. It is unnerving driving on empty.

Joe

 

[midlife]

Sounds like you have a wrong gauge or fuel sending unit. Typically, they have a bias one way or another: your sending unit seems to have a wider resistance range than what the gauge is expecting.

 

[JimNiki]

Randy, what would installing a var pot inline do? Could that help?

He can always buy an electronic CVR with a trim on it and play with that for slight adjustments...

The hillbilly way is to make sure the tank is empty and bend the needle in place.... Hehe

 

[midlife]

Variable potentiometer will work only to adjust the bias, as will an adjustable CVR. I think his problem is different: too wide a range of resistance at the sending unit relative to what the gauge wants to see.

 

[c9zx]

The service manual says in full up position you should read 8-12 ohms, full down 60-86 ohms. The reproduction senders I've checked in the last few years typically read 7.5-75. The electrical assembly manual shows with 4 gallons in the tank the gauge should read just right of empty to just left of 1/4 tank. Chuck