The engine will not turn

4.6 L engine. Does the engine actually spin ( turn over ) but does not fire. Your statement is confusing. Either it turns very little like it is jammed, then I would check the starter, on these models it is very hard to get the 3rd bolt out, (believe me). Or it spins but does not fire up. Then I would check the fuel pump pressure. And, if it spins but does not start, make sure there is spark at the plugs.

Check the Fuel pump. you usually come on when you turn the ignition on.