Originally Posted by thegipper

Sounds like you may have a blown head gasket and your engine may be hydro locked.

Pull the plugs as already suggested.

How is your coolant level? Have you been losing any? Head gaskets generally don't all of sudden fail completely, it's usually gradual. Since your truck sat for several weeks, it may have leaked a bunch of coolant into one (or more) of the cylinders and hydro locked it.

Have you noticed any rough starts after the trucks been sitting overnight in the past?

If you have a leak down tester, you could do that next while you are pulling the plugs. That will tell you for sure whether or not you have a blown HG.

Sorry, but the initial diagnosis doesn't look good (fingers crossed anyways). Who knows, maybe it's some other thing???