My van makes a loud squealing sound in the engine when I crank it up. It is coming from inside the motor. What can cause that? It also does not crank up right away.

High pitched squeal? Could be fan belt, alternator or water pump. If you have not changed the belt in the last 50K miles, that would be my first choice to look at. If it is cracked or glazed and shiny looking, it is time for a new one. They are cheap so that is why I suggested it first.