Does anyone know how to test diode for the pcm that's located in fuse box under hood? Someone said if there are no clicks the diode is probably bad. But I am having trouble finding one. Anyone know who handles them?

I have a 1994 ford f350 with the 7.3 and cannot get it to start. Found the fuse for pcm blown but nothing when I changed it. Unplugged fuel heater but still no start no smoke or nothing. There is no noise when key is turned on. Thinking it could be bad diode.

Thanks
Alton