my 99 cummins fuel gauge acts very weird so i changed the fuel gauge sending unit for 65 bucks and there was no change, it still reads right around 3/4 all the time, i put the whole gauge cluster from my dads truck and pluged it in an there was no change from the original gauge, i put the scanner on it and it said 84% fuel level so the computer is giving the wrong reading. so im thinkin that the wiring from the sending unit to the computer is screwed up or the computer itself.. anyone else have this issue? any opinions are welcomed

 

Yea trace and check the wiring to and from the sending unit. Make sure your getting a good connection (in the plug) onto the unit.

And here's a stupid question mainly for laughs but did ya ever completely fill the tank up?

 

ya i have filled the tank the gauge doesnt go below about 3/4 when i know i have burned almost a whole tank worth of fuel

 

There isn't anything obstructing the float in the tank, is there? Did you try plugin the new unit in, cycling the float and watching the gauge before putting it in the tank? It's always a good idea to test in the open before closing in the problem component.

 

Yea, X2 on pulling the sending unit back out and double checking everything making sure nothing could be obstructing or messing with the unit while in the tank.