Fuel gauge

[davefrancisco]

Apologies if this was already answered in the forums. I looked but did not see my case there.

When the tank is full the gauge reads 4/4. Bounces during acceleration and driving, but don't think that is an issue based on what I have read.
After I drive the car for about 40 miles after a fill up the gauge shows empty, and even the bouncing needle stops. I did notice that the low fuel indicator light will come on when the tank is low.

So is this a sending unit issue, or perhaps a gauge or connection issue?

All ideas welcome.

Dave

[18Fiatsandcounting]

Hi Dave, it's most likely an issue with the sending unit, but I wouldn't rule out a poor connection. The sending unit over time gets crudded up with scale or the like, resulting in an erratic reading or no reading at all. The gauge needle shouldn't move when accelerating/decelerating/bouncing, and if it does, again, usually a crudded up sending unit or the unit has lost its ground connection, which in this case is the tank itself. If the tank loses it's ground to the body, that can cause issues too. To check either, run a ground wire from the sending unit to a good ground spot on the car body, when the gauge is reading empty but the tank has at least a few gallons in it, and see if the gauge needles moves.

It's unlikely to be a gauge issue if the gauge reads full when the tank is full, and the low fuel light works as it should.

I have taken apart sending units and carefully cleaned them up, but most people find it easier (better use of your time) to just buy a new one. They're not terribly expensive, $60 or thereabouts.

-Bryan