A good friend of mine has a 2000 F-250 7.3L PSD. The truck has been running good, starting good, but last night after making a 20-min stop, it wouldn't do anything when turning the key. Dash lights, door chime, headlights all work, but no cranking, nothing, not even clicking except for once. Even though the batteries were replaced last fall, I suspect battery/contact issues, but I don't know much about diesels. Any other ideas/suggestions? Thank you.

 

Check fuses and battery contacts

 

If the fuses check out OK take a look at the neutral safety switch.

 

Use a screwdriver across the relay for the starter post. That will get power to the starter. Check the small post with the angled boot and small wire to it with a test light. It should have power when you turn the ign switch

 

You can try all that OR you can try this:

-Turn the key to the first position
-Put the truck in reverse
-Roll it back a foot or so
-Put it in neutral
-See if the truck starts

 

I had the same issue that would strike at random. I checked fuses, relays, etc. and for me it was loose screws. Seriously. When they get loose enough the shifter doesn't go fully in to park even though the tranny is in park. Even if it's not these screws, it won't hurt to make sure. Here's a pic for you:

 

Thank you all for your comments and suggestions. Moved the shifter around in park, and it started fine - will check the screws that papadelogan mentioned and go from there to make sure that it always starts consistently.

 

Yep, when I was having my trouble that was the same symptoms I had: in & out park a couple times and she'd start. After tightening those nuts.... no more issues. Let us know what fixes it for you.