1995 Ford E-Series Van • 200,000 miles

I just replaced the starter with a starter from the local parts store but the new starter won't engage the fly wheel. I had the new starter checked and it is working properly. When I hooked ti up to the power on my van and grounded it to see of the gear moved when I turned on the key switch, it did. However whin I bolt it up to the engine it makes a noise like it is working but it does not engage the flywheel. Any ideas on what might be the problem?
February 3, 2013.

Check the ground between the battery and the engine block. Are you sure the wiring is correct to the solenoid?

As I said before when I wired it up I grounded it to test the bending gear before I bolted it up to the engine and it worked correctly. I also checked the flywheel to see if there was any damage and there wasn't. I turned the flywheel by hand to see if another area might engage. However none of these things has helped to get the starter to engage the flywheel.
When I measured the gear it appears to be about a 16th to a 32nd different placement than the original but I'm not a pro and don't know for sure.

Feb 3, 2013.
The clearance between the flexplate and drive pinion is too excessive-try shimming it closer using shims-trail and error till the starter engages the flexplate w/o grinding noises-

Feb 3, 2013.