I've had that problem on two different F150s. First turned out to be the fuel pump relay....rotted wires and bad connection . Second was on humid days , usually first time startup in morning and after spending $346.00 at the dealer with no fix. changed the distributer cap and rotor, after seeing blue sparks on the coil connection to cap, everything now works just great. First turck was an 89 with 302, and present is a 96 with 351. Dave G

 

Had the same intermittent no start problem on my wife 5.4 Expy. I found that it had two problems.. The throttle body was gummed up around the butterfly plus the IAC was sticking closed. These two together wasnt allowing any air into the engine.
I could crack the trottle alittle and it would fire right up..

Cleaned out the throttle body and cleaned the IAC and all was well.

Also saw a weird nostart in a EECIV 5.0.. The TPS was bad in the idle postion causing the computer to think it was in wideopen position. The computer then went into flooded engine mode and cut the gas off at startup.