I have a 2004 F350 with a 6.0 Diesel engine. Sometimes when i go to start the vehicle I turn key and nothing happens. Battery has a full charge I use a screwdriver to jump across starter and the vehicle starts. It does this if engine is cold or hot but doesn't happen all the time. Any ideas would be appreciated.

 

I had a 99 Expedition that did that; problem was a loose battery cable. Maybe take them all off, clean up the ends, and hook it all back up.