Found this from another thread (viewtopic.php?f=1&t=61588&p=505305&hilit=+simple+test#p505305):
Eugene wrote:Basicaly you have a standard battery operated ignition system. Some place along the line the coil in the magneto has been disconnected and an external coil added.
A simple check first. Remove the wire from the side of the magneto. Remove the wire from the center of the distributor/magneto cap and lay it next to the engine block so that you have a 1/4" gap between the end of the wire and the engine block. Turn on the ignition. Touch the wire removed from the side of the magneto to the magneto. Then remove. If there is a spark the problem is in the magneto points.
No spark. You need a test light or multimeter to check out the ignition system. With ignition switch on, starting at the wire from the side of the magneto - start checking for battery voltage at each junction/connection - tracing the wiring back to the battery. Once you find battery voltage - the problem will be the previous appliance or wire between the voltage and the previous junction/connection.
While trying to do this, I discovered two of the four spark plug wires (#1 and #3) with burned ends at the rotor cap; points inside of the cap also show evidence of burning. I tried the simple test above and got no spark.
Need some clarification:
1. The test above says to "Turn on the ignition." Does that mean only turn on the switch, or turn on the switch and engage the starter?
2. What's the purpose of placing the center wire 1/4" away from the block?
3. Also, if no spark, could it be due to the burnt out points under the rotor cap?
4. I have a multimeter. On the advice above, do I leave the black lead from the multimeter on the side post at the magneto and start using the red (positive) lead at each electrical connection until I see voltage?
5. Can I test the ignition coil while it's still connected to the tractor's wiring or do I need to remove the wiring to/from the coil?
Sorry for the length of this post. Electrical issues always seem to intimidate me. Any help is, as always, appreciated.