The common fault here is the fuel tank senders. There are two in the tank and are only available from the dealer last time I checked. Don't quote me on the price, but I think I remember them being in the $200 range for the parts. If you do a search, you should be able to find more discussion on the matter.
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record