I have never had probs with a Chevy gas gauge, but have fixed alot of Ford?mopar ones. Every one I have worked on, straight ground to the sending unit makes it read full, not empty. Most of the ones I have fixed, involved the windings on the sending unit breaking, killing the ground path resulting in an empty reading. Sometimes the float will stick, usually in the down position,when the tank has sat empty for a long period of time. Never seen a float stick in the up (full) position, but I guess it is possible.