You probably need the help of someone that has their 5.0L efi in a Stang.
I can tell you what happens in my Volvo install if you like. When I turn the key from off to the 'ignition on' position, my ecu provides ground to the fuel pump circuit for about 2-3 seconds, then, if it doesn't sense the car turning over, it shuts the fuel pump off. I believe it looks for output at the alternator to determine if the engine is turning over.