Pin# 1 is always hot.
Pin# 2 is normally off.
Short between Pins 1 & 7 to crank starter.
A starter switch should be beefy enough to handle the inductive kick of the solenoid. Use a wimpy switch and it will burn out or weld itself into the closed mode.
Get one of these to round out your diagnostic tool collection -
Thanks to 02 Les for the schematic and to whoever took the pic of the plug. (Is that car Stella?)
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-Jerzy Socha