1991 Ford Taurus Engine won't start after 2 hours

I am thinking either the neutral safety switch or the starter solenoid. You can test the solenoin easily enough if you have a jumper wire. If you jump from the S terminal to the starter wire (the wire going to the starter) and see if the starter turns if so then the solenoid is bad. If it still don't turn then go to the starter and jump the b and the m terminals on the starter and if it still don't work then the start is going. Here is a diagram of the system hope this helps.