Fuel guage Question

[bchauvette]

What in the fuel gauge circuit stops the needle from swinging back and forth as the fuel sloshes in the tank?

Fuel gauge fundamentals;

Think I have the fundamentals on how a fuel gauge work. The sending unit has what amounts to a wire wound
variable resister. There is an arm with a float on the end that, guess what?, floats on top of the fuel in the tank.
The other end has a metal tab that rubs against the variable resistor wrapped wires. This up/down, back/forth action
changes the resistance of the assembly. The gauge is nothing more than a volt meter. A voltage is applied to
one gauge terminal. Not necessarily 24 volts. The other terminal is connected to the sending unit variable resister.
The other end of the resister is connected to ground. As fuel level changes the resistance changes, the voltage
changes, the needle changes.


Back in the day the needle would swing up and down as the fuel sloshes. You had to kind of estimate how much
fuel you had. If the engine quit you pretty mush where sure you ran out of gas! Actually not so funny. Model A's had a
reserve setting on the shut off.


B.T.W. Every so often my fuel gauge needle pegs full for a second. Using the above explanation more than likely
there is a short on the Gauge to sender wire or the sending variable resister is shorting.

 

[cranetruck]

There are baffles inside the tank to keep the sloshing to a minimum. You probably wouldn't notice an inch or two in the level change.

 

[VPed]

The pegging every so often is probably a bad connection between the sender and the gauge. Check the Packard connectors. You can squeeze them slightly with pliers to make them tighter connections. I had the same thing on oil pressure gauge on one of my trucks.

 

[wreckerman893]

The only thing that lies more consistently that a career politician is a military vehicle fuel gauge.

 

[74M35A2]

Needle wavering is normal, as it is direct reading with no dampening circuitry. Going to the pin is not. Check the ground wire from the frame to the sender flange, I forgot if that is bad the needle will pin one way or another. You may also want to wiggle all 3 connectors and see if there is a change. 2 on the gauge back, and the one on the sender. Others here are correct also. I had both a bad gauge and float simultaneously. That was frustrating to figure out.

 

[SCSG-G4]

Also, mounting the float in the middle of the tank (front to back and side to side) lessens the effects of sloshing, but the fuel pickup also needs to be at the same spot to be effective. So some compromise has to be made. Personally, I'd rater the gauge be inaccurate on the low side than the pick-up point be elsewhere (unless the elsewhere was a lower point in the tank).