[tucsonjwt]

There are a lot of threads on gas gauge diagnosis and fixes on this forum, so you could search for them. Someday we should have a tutorial for this issue, since so many people post about it. Everyone suggests checking the ground wire on the frame rail first, which makes sense - except it is not easy to reach. Usually, an erratic gas gauge turns out to be the sending units - but I recently replaced both my sending units in my dual tanks only to find out I had a bad gas gauge instead. In the future, after checking the ground wire, I will replace the gas gauge first ($50 expense), since it is a lot easier and quicker to replace the gauge than the sending units, and you might be able to sell the gauge or return it if it does not work. Aftermarket sending units (Spectra, $40-$50) will cause your gauge needle to bounce when the truck is driven, OEM AC/Delco won't ($140-!80).