Started the truck this morning and when I got home from work after being parked for 20 minutes it won't start. Battery seems fine, I even tried a jump start and still no start. Wait to start light turns on like normal. Before this happened, it was making a rattling or knocking sound when I first start the truck for a few seconds then runs like normal, but now it just won't start. I haven't really done anything because I'm not sure where I should start looking. Any help is much appreciated.