During the summer was in washington didn't crank pickup for 3 weeks when I cranked it to hook up 5'th wheel it started right up ran less than a minute died. fuel guage was on e so changed tanks cranked quite a bit before it started ran fine pulled the trailer back to nevada fine. Sat for 3 days same thing noticed return lines damp ordered kit from napa (ouch) but didn't need pu so didn't gst around to installing them. 1 month later drove back to NM. pu sat for 2 months finally changed return lines yesterday and filter hadn't been turned over in 2 months when finished it started right up like nothing was ever wrong ran rough for a few seconds then perfect figured after opening up the system it would be hard to start (go figure) this morning cranked fine happy again.
now for the bad part went to town last night came back with no headlights everything else worked.
This morning went to crank it to make sure the return lines did the trick ignition switch wouldnt work just turns get in the right position and the glow plugs worked cranked it manually started fine. So now I guess a new switch and headlight repair is in order gotta love these trucks.

 

Check the main light switch for burned up too........ if the connector is burned replace it also the switch if the spade terminals are burned.

Think about....
https://www.ford-trucks.com/article/...r_Brights.html

EDIT...... I believe you have the floor mounted dimmer switch... check it too.