I have a 1986 e350 that is an old shuttle bus with a fiberglass back end. The four orange running lights at the top front of the fiberglass back end stopped working one day. All other lights work fine and fuses look good. I don't think those lights have their own fuse anyway. Any ideas to as why these lights all the sudden went out?

 

Very probably the ground wire is corroded or came unattached. They are wired to your park lights but because the shell is fibreglass, they have to have their own ground wire.