This is how it works on paper: Due to voltage drop while cranking the engine, the voltage to the coil also drops. This causes a weak spark that may not be sufficient to start the engine. To remedy this, we use a lower voltage coil that will provide a nioe hot spark at cranking voltage. Once the engine starts, and the starter load on the battery is removed, voltage rises. To accomodate this, a resistor is used to drop the voltage back to the cranking voltage AT THE COIL. To accomplish this, the start button or key switch has a circuit that BYPASSES the resistor during cranking. So, when you are holding down the starter button, the resistor is bypassed and you have spark to start the engine. When you release the button, the circuit is broken, and the engine stalls because the resistor is probably burned out causing the broken circuit. Surprisingly, these resistors take a lot of stress while in operation, and are a relatively common failure, but not as common as I would have expected.
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Today's Featured Article - What Oil Should I Use? - by Francis Robinson. I keep seein this question pop up over and over again in discussion groups all over the web. As with many things there are often several right answers and a few wrong ones. Some purist I'm sure will disagree to no end with what I will tell you but most of us out here in the real world don't really care do we ? Some of them only bring their noses down out of the air long enough to look down them anyway. If you are like me you are only doing this old tractor stuff because you enjoy it. You
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