I have an old 2135 tractor with a 13B-214F100 Koehler. This tractor is the one with the drive shaft. Got it going well, replacing the bearings in the drive shaft. Ran great. Suddenly stopped firing. Unplugged the ground wire on coil but it still does not fire. I need to know how to get to the coil to remove it. I also need to test or replace the module. Anyone had experience with this tractor? Any help appreciated.