F150 wont go into park have to start it in neutrall

SOURCE: my ef falcon wont restart at operating temperature

does the engine crank over when it stops

SOURCE: 2001 ford f150 supercab will not start park only

Could be 3 unrelated problems.

1. The will not start in park. This seems like the DTR ( digital Transmission Range ) Sensor on the side of the automatic trans is not making contact in the Park position.
Quick test, wheel chock at least 2 sets of wheel on a level surface, with truck in park, and a friend pressing the brake pedal, have them turn the key to the run position.
Wait for the theft light to go out, and on the starter motor relay on the firewall, apply +12 V to the small gauge wire ( orange or orange w/ a stripe of color on it ). The starter motor relay will have 2 large battery cable size wires, and a smaller 16 AWG orange ( w or w/o color stripe ) on it. If this starts the truck, the DTR is the problem.

The orange wire runs through the DTR, and will only allow power to the starter relay in park or neutral. You seem to have a problem with the park side of the sensor.
It is on the driver's side of the trans, with a connector to it. Check the connector for water / corrosion prior to ordering a new one.