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fuel gauge bounce

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NutmegCT

NutmegCT

Great Pumpkin
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Our fuel gauges tend to bounce around when driving. The needle is indicating the (rapidly changing) position of the float in the tank as the fuel sloshes around.

Is there any way to "slow down" the movement of the needle?

Add a simple electronic component in the sender wire which "absorbs" the gyrations?

Add "wings" to the float to give more resistance as it moves in the fuel?

Or ...?

Thanks.
Tom
 
If the float in the fuel tank is a metal can with soldered joints, it is possible that the ethanol has attacked the solder and the float is full or partially full inside the can.

This problem has caused lots of problems with the floats in SU float bowls. I checked mine just last week, removed them and shook them. They were dry inside.

New ones that are made of gas-resistant and ethanol-resistant foam plastic are available but I don't know who has them for sale.
 
My opinion, if it is bouncing so much during normal driving that you can't tell how much fuel you have; then there is a problem with the gauge (sender etc). Mine only bounces that much when I'm driving hard enough that I'm not paying any attention to the gauge. The float is fairly well centered in the tank, so should be relatively unaffected by smaller amounts of 'slosh'.

But if you really want to slow it down, try adding a big capacitor to the sense line. Can be at either end, doesn't matter. 20,000 microfarads should slow it down enough to notice (about a 1 second time constant assuming the equivalent resistance is 50 ohms); I think a full farad might make it too slow. Be sure to observe polarity on the cap. Hamfests used to be a good place to pick up big caps cheap, probably eBay today. Eg,
https://www.ebay.com/itm/MALLORY-CGS203U0...=item5641faa5f5
or
https://www.ebay.com/itm/50000uF-25V-105-...=item35bf93e0c0
 
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