If you have an EFI engine there is little known relay called the EEC Relay ( Electronic Engine Control ) this little baby provides power for the computer. If the relay is bad ( bad or high resistance contacts ) the engine won't start or runs and just shuts off whenever it pleases, a real thrill when you are in the middle of an intersection It mostly shows up as an intermitent no start. I have had the one on my truck go bad ( full of water and rust and yes the engine ran with it that way ) and the one on my wifes 93 ford. The relay is located on the drivers side fender pannel in the engine compartment. It is a single relay about 1.5 x 3/4 of an inch sq. It is located near or on the bracket that holds the 3 large wire harnesses from the engine. I believe it is the only seperate relay there. If you find it rap it with a screw driver and see if your engine will start, this might not be the problem but it can't hurt to look.

P.S. the relay is only $15 or so from Ford

stractor