Ignition Problem

I'm trying to help my son. His wife's Prism will be running and then just stop. No fire at the plugs. He has changed the Dist cap, rotor, and coil. The book says something about an igniter. He had the external one, we found it finally. This thing is right at 200 bucks so I hate to change it if that is not going to cure the problem. Is there some way to test this thing? Any advice would be greatly appreciated.

Pel

get one from the salvage yard much cheaper, could also be the pick up coil in the distributor causing the problem...I suggest replacing both to prevent future problems