What year? Carb or MPI?
Assuming an electric fuel pump with a carb it gets power from the starter solenoid when cranking and an oil pressure switch once the engine has started. This is a safety set up so incase the engine stalls the oil pressure goes to zero removing power from the fuel pump flooding the engine an a potential explosion hazard.
If MPI there is a fuse and relay.
1997 2400 SCR
5.7 Vortec / Bravo 2