The engine will not start. It cranks fine, I have spark at the plugs and fuel pumping from the fuel filter with ignition turned on. I have 12 V. on the injectors. Any Thoughts?

The engine stopped running while driving about 55mph. Hasnt restarted since. Daughter was driving the car so I dont have much info on what occured at the time it stopped running. I read another forum and saw someone post info about possibly the Main Relay. I have yet to locate this in order to check it. Any clues about this as well?
Thanks for helping if you can.