[r_dee_jay]

Bonanza1
Does the engine crank at all. If the engine does crank then is more than likley the injector pump as amafyrfytr said. We have the same 6.2 engines in the Army Humvee. When our engines don't start we poor ice cold water on the injector pump and it starts right up. This could be risky with your truck because there are alot of other electrical components under the hood. So if you want to test this theory then use caution. If does not even crank then it could be the starter.