MikeC, your problem sounds like something is shorted to ground. Try disconnecting the sender wire from the fuel gauge (most gauges will have a terminal marked S for sender) and turning the key on. If the gauge drops now you either have a sender wire shorted to ground or a bad sender. If it does not drop you most likely have a bad gauge. This is assuming that you have a standard calibration gauge. Some gauges will drop to E when you short the sender wire to ground and if that is the case all of the tests will work in reverse.