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Fairbanks Morse Battery Ignition

It looks like a magneto, but it ain't.

Fairbanks Morse built these battery ignition units that essentially are a modern distributor, points, coil and condenser all in one. They did not need the heavy duty impulse coupler to control advance and retard, rather they used a centrifugal weight advance much like a modern distributor. Unlike a magneto where feeding power to it is a big NONO, these do not generate their own electricity. There is a big wirewound current limiting resistor mounted on the side where power is routed when the ignition switch is turned on to start and run. In contrast,the terminal on the side of a magneto is disconnected from ground to start and run. The upside to this unit is a hot spark even at low cranking speeds as the power is supplied by the battery. The downside is that coils can overheat and be damaged by leaving power connected without the engine running.The later externally mounted oil filled ignition coils were much more robust and forgiving. Dry type coils are fairly expensive and susceptible to cracks, internal faults and subsequent moisture damage and insulation breakdown. Here is some factory information listed on the links below for care of these units with permission from Fairbanks-Morse: