Last week was given a 51 case that has been sitting for 10+ years. The tractor has already been converted to a12 volt system. Rewired everything exactly how it was. Did a full system check and I have power everywhere. I have power going to the coil and leaving the coil, but can't get spark out of the coil. Thought it was the coil. Tried another coil off of another tractor that is good, and still no spark. Put the 2nd coil back on the original tractor and it works. My father-in-law is a mechanic and ran a test on the coil and the tester states it is good. Do you have any suggestions as to what would be wrong? I am determined to make this tractor run!