Fluctuating fuel gauge

[Mastiff]

Suddenly my fuel gauge seems to be hyper sensitive, like it goes up and down when stopping and starting. I'm thinking that there must be some sort of filtering on the signal from the sender to average this stuff out as the fuel sloshes around? Is there a capacitor or resistor or something that is likely to be out?

Thanks.

 

[ryan22re]

Ground back at the tank is probably going away.

 

[dyeager535]

I've dealt with this problem. Hypersensitive gauge is a gauge problem. If it were a simple on/off problem I'd say external wiring, but in my case, slowing down, starting to move, hitting bumps, etc., all caused the needle to bounce wildly.

All damping is in the gauge, and NO gauge when working correctly, no matter what happens to the external wiring, will fluctuate that fast. No "modern" GM fuel gauge is setup to allow fast changes in fuel sender signal to be reflected in the gauge just as fast.

There is a resistor on the back of the gauge, but as far as I can tell it was used to "tune" the gauge, since you will find them with varying amounts of resistance, and they appear to be color coded like fuses. By tune I mean fine tune the E and F position.

 

[Mastiff]

Ever heard of people repairing them, or do I need to hit E-bay for a new gauge?

I've dealt with this problem. Hypersensitive gauge is a gauge problem. If it were a simple on/off problem I'd say external wiring, but in my case, slowing down, starting to move, hitting bumps, etc., all caused the needle to bounce wildly.

All damping is in the gauge, and NO gauge when working correctly, no matter what happens to the external wiring, will fluctuate that fast. No "modern" GM fuel gauge is setup to allow fast changes in fuel sender signal to be reflected in the gauge just as fast.

There is a resistor on the back of the gauge, but as far as I can tell it was used to "tune" the gauge, since you will find them with varying amounts of resistance, and they appear to be color coded like fuses. By tune I mean fine tune the E and F position.

 

[dyeager535]

You probably COULD somehow, but I've never bothered to de-rivet the face of the gauge from the "can" the guts are housed in, to see what could possibly be wrong in there.

I believe there are at least a couple posts saying that the resistors on the back of the gauge failed, and just replaced that and were good, but I can't recall what their symptoms were.

Ebay, local 'yard, local parts for sale, or parts for sale forum here. Dime a dozen, and easy to strip from a cluster.

 

[diesel4me]

baffling?...

Maybe the baffles in the tank broke loose,and is letting the gas slosh around too much?...

 

[Mastiff]

Maybe the baffles in the tank broke loose,and is letting the gas slosh around too much?...

No baffles in my diesel 86 CUCV.

 

[dyeager535]

There are no baffles in anything pre-TBI (that I'm aware of, and I've had a few tanks apart, cars and trucks, although some cars have a small plate at one end) so that's ruled out. The gauges are damped, the float for the sender is moving all the time, even baffled TBI trucks have the sender float outside of the fuel well.