truck shut off,wont restart,when ign.sw.turned on it blows 30a.fuse right away.

What is your question?

mechanic has tried to check injectors,glow plugs,and the injector pump.my question is could there be a bad wiring harness in there somewhere that could have wire shorted to the metal part of the truck from rubbing possibly .he is having alot of problems troubleshooting why fuse continues to blow.i would like to get it back because i have it sold possibly.never had any major prob. with truck before now.it has 123,000 on it new tires, runs real good just wont start, please help