I just bought a 2001 2500 HD the truck won't start the first time you have to turn the key 2-3 times letting the fuel pump cycle before it finally starts, when i fill the truck up it jumps from full to empty. So is it the sending unit would that affect the fuel pressure to the motor or i have no idea what im talking about!

 

I would think that a fuel pressure test is in order. Seems like the sending unit is going bad and also the fuel pump. Sometimes they are integrated units and other times they are sold seperately.

 

test the fuel pressure, i think it should be around 60, could be a drainback problem, the sending unit is probably messed up which is the same module as the pump

 

So i should go ahead and buy the whole sha bang just to be safe? I found the part on JC whitney.com 169.99 free shipping