Duty Solenoids

The duty solenoids are solenoid valves that are operated by the control unit. They open and close at a constant rate of 40 cycles per second, though the "on" time can vary. When the engine is being monitored by the control unit and oxygen sensor (closed loop), the average "on" time is 30-40%. This time can be measured with a dwell meter and is what determines the air/fuel ratio.

The duty solenoids are located on the intake manifold and connected to the carburetor by air hoses. A small air cleaner is provided to filter the air which enters the carburetor through the duty solenoids.