Ford: 2004 F150 v8 will start but will only run for a few seconds, inertia switch, crank sensor

Question
My son's 2004 F150 V8 will start but won't continue running.  My son was driving down the highway when the engine suddenly quit.  He was able to restart it for a few seconds as he coasted on the off ramp.  I attempted to start it using ether but it did not even fire.  The engine will crank over but normally it doesn't attempt to start (no fire).  Occasionally, typically after the trucks has set for a few days, the engine will start and run - only for a few seconds.  Additional attempts to start it result in the engine only turning over - no fire.  Also, the code reader shows no codes.  My son indicated he filled up with gas approximately 30 minutes before the engine quit.

Answer
Hi,


We need to see what the fuel pressure is at the schrader valve on the fuel rail.  Key on engine off, fuel should at least spray out for a sec when the valve is depressed.

How is the spark?

Most commonly, 1. Fuel Pump ( people continue to run their tanks too low- this kills the pumps rapidly and without warning)
2. Crank sensor

3. Inertia switch bumped= this shuts off fuel pump.