My 24 valve cummins won't start without starting fluid. Cranks over and over. Spray a little fluid in it and fires right up

 

Bad fuel pressure or is draining back into the tank

 

Your lift pump is probably failed, not feeding any fuel. Rotary type injection pumps, like your VP44, are capable of sucking fuel from the tank even if the lift pump is dead. Engine runs, but performance will suffer. And starting fuel gives enough rpm's for IP to suck fuel at the start-up.
How many miles on your truck? When was the fuel filter changed? But start by checking the fuel pressure.