I have a 7.3 that starts fine in the morning or has be off for a long period... but when I shut it off after it get to running temp it will not start unless u pull it off.. what could be my problem?

Sounds like an old, tired fuel pump. Pump clearances may be increasing when it heats up, causing the fuel pressure to drop. Try installing a new Motorcraft fuel pump. I would also replace the under hood fuel filter and the fuel filter on the frame.