Anyone have any ideas what might cause intermittent non-starting of this car. Started it, test drove it, loaded it on trailer, unloaded, ran it several times. Let it sit for a few months and now it won't start.

smokin5.0
I think more info is needed on what the car is doing or not doing.. If the car does crank try sprayn carb cleaner at throttle body , if it starts you have a fuel issue? pump /relay/elect connection?.... if not it may be spark ??? dist module, ign switch ?
Check for fuel psi at fuel rail port by pass valve cover , check how strong the spark is at coil/dis.

hope some of this helps;)

Check to see if you can hear the pump running when
you turn the key on. That's what it was the last time...

Yeah.....unfortunately I was alone when trying to do this last.....so the carb clean trick in throttle body was not possible, and neither was listening for the fuel pump, however, with that said, I don't recall hearing it. Most Mustangs you can hear the pump from inside the car with the door open. It sounds like it wants to go.....cranks and cranks just won't fire. I was going to try replacing ignition module on the distributor, but with the SSP oil cooler lines...it is not an easy 5 min job like on a regular 5.0. I might try ordering a new relay....maybe the relay is working intermittently, hence why I don't recall hearing pump come on. Where is the fuel pump relay located again?

The fuel pump relay is under the drivers seat.
You should hear it click on whan you turn the key, and you should be
able to hear the pump run for a few seconds. Most likely the new pump
went bad, just like the last one did, as it sounds like the exact same thing
I went through with it...