....it's time for all good pumps/sending units to goto heaven..."
being a 93 i'm betting that your float has just gone bad (brass,fills with gas and sinks)but if your truck still runs then the pump is still good of course .to replace the sending unit you have replace the pump ( they sell the sender by it's self but it's self ( hard to find...somewhat) but whenever this happens it's best to replace the entire unit ...pump and sending unit as a whole .
but this is all if the sending unit is bad ....maybe it's the guage but like i said 8 times out of 10 it's the sending unit ...how many miles on the odometer??? over a 150k ??? , if so then it's time to replace the pump .
you could try filling the tank about half full and have someone on the bumper in back hop up and down and watch the gas guage and see if it moves from fuel rolling around ,could be that the float is stuck but like with mine ( a 94) the brass float was filled and you could see a small pin hole from corrosion .
to check if it's the guage it's self thats the problem ,check the connection at the pump and see if your not just got a loose or bad / damaged connection ( located on the left frame rail past the shock and a little past the axle tube .the connection has a plastic keeper that holds it to the frame rail ( you'll need to remove that keeper to gain better accces to the harness)
search for pump replacement in the forum ...but i can tell you there are 2 methods for removeing the pump both have there up's and downs ( i lowered my tank when i did mine ...not that bad but it's got it's downside) .
whichever direction you take just remember one thing .....
BUY A QUAILITY PUMP.
i bought a chepo unit when i did mine and it's failed 3 days after i installed it so i had to go buy a name brand pump ( bosch ) and look into a pump that offers a lifetime replacement ...thats what the bosch is ( got it at advance auto) but regardless i had to do it twice .
goodluck
edit : looks like dillion beat me to it
. Hopefully you can get the sender swapped out soon 
