1994 Ford Truck engine does not turn on

Engine Performance problem
1994 Ford Truck 6 cyl Front Wheel Drive

this is a diesel 3.9 engine, after running engine does not want to restart until it cools off for a half hour, last time waited 4 hours and still no start, so I had to tow it
AS FAR AS DONATION I BEG TO BE EXCUSED FOR THIS IS WHAT PUTS FOOD ON MY FAMILY TABLE AND I PRAY TO GOD FOR YOUR HELP
KINDEST WISHES AND REGARDS
hANY