Posted by Johnd [71.246.83.229] on Sunday, November 01, 2015 at 07:40:14 :
In Reply to: Re: I did check heat buildup posted by Willy-N [72.171.192.60] on Saturday, October 31, 2015 at 22:51:30 :
All coils run on 9 volts. An external resistor coil get 9 volts at the plus terminal on the coil. An internal coil gets 12 v at the plus terminal, but the internal resistor immediately drops it down to 9 volts,
When you are cranking the starter, most times the battery voltage drops to maybe 10 volts or so. This causes the 9 volts inside the coil to drop down to 7 volts or so. This can cause bad starting problems. Ever had an engine that would only fire when you stopped cranking the starter? Just before the engine made that last turn, it would start and run great. That is due to low coil voltage while cranking the starter.
The fix??
The older vehicles would have a connection between the heavy starter cable and the coil plus terminal. This connection served to bypass the coil for a few seconds only while cranking the starter. This raises the coil voltage input from 7 volts to 9 volts in my theoretical example.
i would not replace the coil with an internal resistor because you won't have any access to the internal connection where the resistor connects to the coil.
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