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Re: spark coil questions


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Posted by rvirgil_KS on November 23, 2021 at 15:03:33 from (8.36.240.238):

In Reply to: spark coil questions posted by Bob N.Y. on November 23, 2021 at 14:06:20:

I'm assuming the distributor is similar to 1940's and later tractor systems and uses the common can type coil as shown by many suppliers when searching for Model A coil

Question 1: With the key on but engine not running, should the voltage on the distributor side of the coil be the same as the battery side? It depends. With points open the voltage at distributor side should be near same as battery side. With points closed the voltage should be near zero.

Question 2: If the voltage on the dist. side is considerably lower than the batt. side, does that mean the coil is hooked up backwards? No, Most likely reason is that points are closed. The coil doesn't care which way it is hooked up. Coil hook up affects the polarity of the spark plug. With negative ground system, - on coil goes to side of distributor, with positive ground the + on coil goes to side of distributor. Hooked up this way, the spark plug will spit the spark from center electrode to the grounded tab. Reverse connection on coil and plug will suck the spark from tab to center electrode. Spark is more efficient if plug spits rather than sucks

Question 3: Is there a difference between a coil designed for positive ground and one designed for negative ground? No, see explanation in #2.


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