You have a "float" in the gas tank, with a resistor relaying the fuel level to your gauge. Sometimes the float is disconnected are simply need replaced. I would have a repair facility check it out.
A. J. Valle
〉 Answered on Jun 27th, 2012 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions
It sounds like you either have a problem with the gas gauge or with the float in the tank.
〉 Answered on Jun 27th, 2012 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines