When I got my '90 Monty the fuel gauge only worked when the tank was full, then at about 3/4 of a tank the gauge dropped to empty. I pulled the sender (an easy job, because Mitsubishi put an access plate on the floor above the gas tank). I tested the sender with an ohm meter and it was bad--had rust in all the wrong places. Got a new sender from the local Dodge dealer (can't remember what I paid, seems like around $60-$70) and installed it. Because of the access plate this whole job is very easy. While you're in the area you might clean all the electrical contacts including the fuel pumps. In fact, like Bob said, cleaning the contacts might fix the problem, without you needing to replace the sender. Good luck, let us know what you find.