The Stovebolt Site Forums The Shop Area The Electrical Bay crazy gas gauge

here's the situation:

last fall i installed a new wire harness, and afterwards the gas gauge was stuck on approx. one-quarter tank. hummmm. so a few weeks ago i removed the sending unit from the gas tank. the float had fallen off, cool. so using a monojet float (i had laying around) i tied it to the float arm. the sender works like it's supposed to (1-32ohms).

when i installed the sender back into the pickup, the gas gauge works now except the lowest the gauge will register is still a 1/4 tank. when the ignition is turned off the gas gauge will fall to empty.

the pickup has been converted to 12 volts (a long time ago, and the gas gauge has always worked).
the only change that has been made is the installation of an altenator in place of a generator.

i'm hoping the installation of a resistor will cure this problem

any comments?

pictures are on my web page under the 1950 chavrolet.

Have you tried adjusting the float arm so it sits a little lower in the tank?

I installed a new sender for my '48 which has the tank between the rails and isn't as deep as the behind the seat type. It read correctly when it was full but when it got near empty, the float was sitting on the bottom of the tank and still registering 1/4. I decided to bend the arm up. Now it reads 3/4 when it is full. My buddy says they were all off anyway so I should live with it.

Yes, my mistake, it is suppose to be adjusted so it is higher in the tank,,,,(I must have been standing on my head!) :o
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I got to thinking,,,,just recently(I know,beginners luck :p )The fuel guage in my 72 has started acting up only reading half when it is full,the tercel my wife drives is doing the same thing.Her 260-Z quit registering at all,and the fuel guage in my nephews car was constantly reading 3/4 full(until he tried to fix it)now it doesn`t work at all!
Must be a new additive in the fuel now days!

Sounds like you have excessive resistence in the circuit. TAke the wire off the sender, turn the key on, now ground the wire. Tank should read full. Remove the wire from ground, tank should now read empty. ( I may have that backwards, ground might read full, but that is the procedure.) Don't worry about grounding the sending unit wire, the voltage flows thru the dash gauge first, acting as a resistor. If the tank will read completly empty with the wire disconnected, you have a problem in the sending unit. Otherwise the problem is in the dash or wiring. Alt. conversion should not affect it.

Good trouble-shooting instructions, Curly. The solution to my problem above would have been to shorten the arm. That way it could swing further down at empty but still float horizontal at full. This solution works only if your tank is too shallow to let the arm point far enough down.

well i tell ya, when the sending unit was removed from the truck (note pics on home page) the unit would register correctly (1-32 ohms).

when i would ground the sending unit wire (0 ohms) the gas gauge would register 1/4 tank

when i would short out the sending unit wire (inf. ohms) the gas gauge would register past full.

when i turned the ignition off the gas gauge would read empty.

next week when i recieve some misc. parts i will invistagate this furter.