My genie garage opens past the screw. When I close the door the screw free spins.

You need to go here for the troubleshooting guides: Garage Door Troubleshooting | Garage Door Problems | How To Repair Garage Door (http://www.geniedoor.com/troubleshooting-guides)
You will need to get your model number so you are looking at the correct manual. It would seem that the mechanism would have a way to detect when it is at the end of the screw.