You'll be glad to hear, you don't have a M/C solenoid. The wire that plugs into the carb is hooked to a temp sensor in the thermostat housing. What you have is called a dual-capacity accelerator pump system. The carb acts like it has a larger accelerator pump when cold. When the coolant temp reaches 170 degrees, the temp sensor sends a signal to the carb to open a valve and then it will act like a regular accelerator pump.
If you are refering to the pink wire that plugs into the bat terminal on the distributor, it goes to the ignition switch circuit.
------------------
Mike
1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site