My fathers has had trouble starting his F-250 on two occasions now. Both times it had been running for about an hour. He got out to run into a store. When he got back out it wouldn't crank. He gets full power to everything on the inside. When he tries again about 10-15 minutes later, it works as though nothing was ever wrong. Any ideas what the problem is? The engine is a 5.4 and I think it's a 2002.