I have a ford econoline 6.0 diesel engine, when warms up if you shut it off will not start, you have to wait until cools down. It runs fine, is just if you turn it off will not start, but if you spray into the intake manifold then starts.

It is often a sign of a tired pump. As they heat soak, inside pump head clearances increase and it no longer develops sufficient fuel pressure at cranking speeds. While it's running, the fuel helps it cool by carrying the heat away. Also, ensure the fuel filter fittings are not leaking. The troubleshooting steps, in the link below, may help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281