Tractor Repair: Ford 8N, ford 8n, copper strip

Question
This tractor was recently converted to a 12 volt system, and a resistor was added in the circuit between the ignition switch and coil (it has a front end distributor).  It began sputtering one day and then stalled.  It sounded like a fuel problem, so I replaced the fuel filter and checked the float and tried to start it.  Turns out it was not fuel but electrical: it has no spark.  It is getting power at the coil, and I check the points, replaced the condensor, and the rotor and cap are new and the rotor is turning.  I checked the resistance of the coil which is O between the feed and main output, and about 12k between the main and secondary, and between the feed and secondary.  Any suggestions?

Answer
Hello,

  These tractors shouldn't need to be converted, but whatever, everyone has their own preference.  Make sure the battery polarity is now negative ground instead of positive to avoid burning the points.  Also make sure the correct type of resistor was installed. There is a paper-thin copper strip that connects between the points and the coil connection, and that sometimes cracks and breaks the circuit.  The coiled prong on the coil can also short against the distributor when the coil is installed. The only good way to replace points and condenser is to remove the distributor, so I'll assume you did that.  If the points don't look perfect, replace them also and gap them to .019 - .020  I would have recommended replacing the condenser, but you already did.  Although I once had a new one that was bad right out of the box.  Unfortunately, you can't accurately test a coil with an ohm meter.  The only way to verify if it's good or bad is either to try a new one, or have it tested on a coil testing machine at a repair shop or auto parts store.  If it's good, a spark will jump continuously across a wide gap on the machine.  These coils seem to me to have a high failure rate.  If they have paint on them, they fail.  If someone leaves the key on without the engine running, they fail.  Sometimes they fail for no apparent reason.  With the distributor removed and the wires attached, you can spin it by hand to check for spark after a repair before reinstalling it.

                  Good luck,

                      Arnie