Expanding on what Kevin said ...
1957 3100. 235. Stomp starter. 12v
This stomp starter has a small terminal just below the large connector for the battery cable. (I have been told that different configurations exist)
It is my understanding that this small connector/wire (purple btw) is connected to the ignition switch to provide 12v at the coil only during the time when the stomp starter is engaged.
Correct so far?
Not exactly. The purple wire connects the 12v battery + lead at the stomp switch to the coil + terminal while the stomp is pushed. Provides battery voltage to coil + during starting.
Then when the starter is inactive, the coil is fed through the firewall mounted resistor and runs at about 9.6v +/-.
Correct?
Yes, correct. If you test coil + to ground with the key on and the engine NOT running you should read battery voltage if the points are open and around 8 volts if the points are closed. If the engine is running and you are using an old analog meter (that has a needle pointer) you'll probably read somewhere around 9.5 volts. A more modern digital meter will bounce around all over the place, especially at low engine speeds.
Disconnecting the purple wire from the starter but leaving the large battery cable attached and checking voltage....
12.6 at the large lug on the starter.
10v +/- at the small terminal on the starter with no wires attached and with the starter engaged.
Shouldn't the voltage at the small terminal be 12.6?
Yes it should, BUT did you check the "large lug on the starter" with the "starter engaged"?? If not, try again measuring the large lug to ground while the starter is operating. Leave the purple wire connected on both ends, but remove the high voltage coil to distributor wire to keep the engine from starting. Also, make sure your + meter lead is touching the "lug" on the starter switch that the battery cable is attached to, not the nut or the cable.
