I have a 1941 9N (12V) that currently will only run (Produce spark) if the starter motor is engaged. It has been running perfectly for the past few months, and then the other day, about an hour after using it, it suddenly would not run unless the starter was engaged. I have tested the battery, bypassed the key switch, and the resistor, and have even tried running a wire directly from the battery to the coil, but with no luck. There is constant power to the coil, as long as the key is turned, but for some reason the spark plugs quit sparking as soon as the starter button is released. It produces good spark when starting, but dies immediately after. I've have done what other related posts suggested, but still can not get it running. Please help!