@jimbo1943 could be an issue with your fuel sending unit, the wiring or the gauge itself. The sending unit is a float like device with a resistor connected to the float and mounted inside the tank.
[image|872442]
and it is there that I would start my trouble shooting. Since you dfid not give us a whole lot of information about what model your PU is or what engine size etc,I can only give you the resistance from the shop manual for a 4x4
For a 17.17gal 4x4 tank at full the resistance is 3 +- 2/3 and at empty the resistance is 110 +-7.7. So use your multimeter and check to see if that is what you get. Or you could go out on a hunch and replace the unit....