Because the ground runs along the high tension lead the chances of the spark traveling down the sensor leads are very slim. It might be possible if you removed the ground from the high tension lead inside the ignition box and ran it to the engine case. I chased bad spark plug boot problems all last summer and the hall sensor never failed. This was an RCEXL ignition. The trouble is probably a bad boot. I had very similar symptoms. The engine would start, idle for a few seconds, and quit. Then it would be impossible to start. Pulling the plug would show that there was spark, but under compression spark would actually occur in the boot. This was with a boot I made myself. The first one I made ran for 2-3 hours. Two subsequent preplacements worked for minutes each. I replaced the ignition with one that had the 1/4-32 boot already.