Posted by KEB on October 18, 2007 at 21:17:40 from (72.19.170.5):
In Reply to: Ignition coil posted by Leckster on October 18, 2007 at 19:39:24:
Assuming the ignition switch is on, there will be current flowing through the coil whenever the points are closed. Engines normally stop with the points closed as one piston is coming up on a compression stroke. If the engine isn't running, its normal for the coil to get warm, but not so hot that you can't touch it.
Whether or not the coil case is grounded is immaterial. The return path for the high voltage pulse is through the condenser and the wire to the distributor. The ignition coil and condensor form a resonant circuit which results in a higher voltage spark than just a simple coil. There is no electrical connection to the case of the coil.
First thing I would do is replace both the points & condensor. Its a cheap way to eliminate a couple potential problems. A bad condensor will cause a weak spark, since the circuit is no longer resonant. Look carefully at the points, the contacts should be smooth. If there's a mound of metal on one contact and a corresponding crater on the other, the condensor is either bad or the wrong value. If both contacts are black and pitted, there's too much current flowing through the points, probably because you're using a 6 volt coil on a 12 volt system without a ballast resistor.
By the way, never clean ignition points with sandpaper. It'll leave abrasive particles embedded in the contact surfaces & cause early point failure. If you can't find an actuall point file, a metal nail file will work. If you have to file points, they're on their last legs anyway & you might as well replace them.
As John T noted, if you have a 12 volt system you either need a coil that's marked for 12 volts or a ballast resitor between the ignition switch and the + side of the coil. If its a 6 volt system, you do not need a ballast resistor, and should make sure you use a 6 volt coil.
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