Some 1968-76 models may have an idle speed solenoid on the carburetor. All 1972-74 models have idle solenoids. Due to the leaner carburetor settings required for emission control, the engine may have a tendency to "diesel" or "run-on" after the ignition is turned off. The carburetor solenoid, energized when the ignition is ON, maintains the normal idle speed. When the ignition is turned OFF, the solenoid is de-energized and permits the throttle valves to fully close, thus preventing run-on.
The solenoid used on most 1977-81 models is NOT an anti-dieseling solenoid; on these models, the solenoid is used to increase the idle speed when the air conditioning compressor is engaged.
For adjustment of carburetors with idle solenoids see Carburetor Adjustments, in Fuel System of this repair guide.