If it rotates but the pistons aren't moving, the con rod(s) are snapped. Usually happens when the engine is run without oil and the big ends sieze.
The snapped rod ends will undoubtedly have trashed the inside of the engine, and very likely have poked a hole in the side of the block (behind the starter motor is a favorite place).
New engine required!
phil_saunders(a)bigfoot.com
Phil Saunders, September 2012
