The truck just shuts off randomly and will not start back up immediately?

This problem started out of nowhere one day 2 months ago. I was sitting in Park idling and it died. I thought it was weird to turn it over it fired but was obvious it was missing out. I left the truck came back in the evening the truck started so I drive it home. Shut it off tried to restart same thing. I'd noticed that it wouldn't start if the gas gauge wasn't reading. If the gauge was showing what fuel it had it would start. I've put a new fuel pump in. I've tore down the front of the motor. To check the timing set. No play in the chain and guards seem to be fine. Timing marks on crank and cam line up respectively. I'm sitting to all of this I've also changed crankshaft position sensor and coil pickup plate in the distributor. My dad wants to junk it! I other hand have done all the work just need help to fix it.