the 5.4 has had a history of injectors that leak down causing 1 cylinder to hydro-lock. the symptom starts off like a cranking motor problem, bumping the switch will get the engine past the [hard spot] where upon the exhaust valve opens and the fuel is pushed out of the cylinder. the easiest way to test for this is to unbolt the fuel rail and lift out the injectors from the manifold leaving them attached to the rail.unplug the electrical connectors at each injector.now cycle the fuel pump by turning the key to the ON position and inspect the injectors for leakage. replace the offending injector[s] as required.
NOTES: 1. only lift one bank of injectors at a time.
2. no smoking, a fuel fire is no joke
3. keep an A.B.C. rated extinguisher near by .
4. DO NOT PERFORM THESE TESTS INSIDE A GARAGE OR OTHER STRUCTURE.
SHOULD A INJECTOR DISLODGE FROM THE FUEL RAIL A LARGE QUANTITY OF FUEL
UNDER HIGH PRESSURE WILL BE DISCHARGED.
hint a scan with a misfire at start up code will reveal which bank to check first. passenger side front to rear 1,2,3,4. driver side front to rear 5,6,7,8.