Is the switch on your diagram that is marked "Start" the contact that actuates the starter motor or the contact that feeds power to the ignition coil. (This is on the assumption that it is an older car that uses a single ignition coil and distributer. You have provided almost no information.)
Looks like a grounded FIELD connection. As wired, a 78K08 voltage regulator ( if exists) could feed the FIELD coils.
My Duraspark VR's use a TIP125 transistor in this manner.