Bouncy fuel gauge, 1975 eldorado

[_Cap_]

So my fuel gauge has been actin gup ever since i installed it, about a year ago.  The gauge is acting almost hyper sensitive to the outputs of the fuel sending unit. For example when i lean into a turn or break it will suddenly spike up or down, reacting to the fuel moving in the tank

Is this an issue with the fuel sending unit or a faulty gauge. and if the gauge is there any way i can pull it apart and fix it, or am I best with a new gauge?

Pulling the dash apart soon to install the clock and need to know if i should go ahead and swap the gauge

[Julien Abrahams]

I would opt for something in the gauge. The fuel sending unit changes its resistance based on the position of the float arm. While driving it moves with the fuel,so I would think there is some kind of resistor or something in the gauge that makes it react more slowly.

[benji808]

FWIW my gauge (same car) also moves as fuel shifts in the tank, especially when it's below half a tank or so, and I believe the '76 Eldo I had previously did the same, so it may be the way it is.

[76Caddy]

My Seville started doing this last summer, bouncing from empty to whatever the actual level was.  So far, my Brougham's is still working perfectly.

Tim

[Big Fins]

Mine 'floats' but it's not erratic. Stopping it leans toward an increase, taking off, it leans toward the bottom of the tank and then levels out in a few seconds.

To the OP, I would be looking at the wiring between the sending unit and the dash gauge. I've never looked at the gauge itself, but there has to be a resistor on the back of it to control the needle. Maybe check the values and see if it's a matter of just replacing the resistor.

[TJ Hopland]

Maybe check the grounding at the tank?  If the ground wire isn't working its depending on the mounting which will be vibrating and getting different pressures in different places as the car is moving and the gas is sloshing. 

You could also disconnect the sender wire and try test drives with it grounded and not grounded to see if the gauge still moves around when you drive.

[_Cap_]

so looking at the diagram it seems that the likely thing is a bad resistor inside the gauge itself, so id likely have to change the gauge to one that hopefully works

[The Tassie Devil(le)]

The vehicles that have a fuel gauge that is not subject to large differences in level measurements I have found use a float that is encased in a tube with tiny relief holes so that the fuel level remains relatively stable inside the tube during turns.

My own '72 Eldo has the float problem, and as the tank gets low, I am always thinking that I should stop and fill her up again.

But, I have learned that resetting the odometer Trip Meter at refilling, I don't have to start worrying until I have driven 550 Kilometres when on a long run.   Around town it is a bit (lot) less.

Bruce.