Idle Speed Control System Non-Calif., Carbureted

The ECC control unit controls idle speed according to various engine operating conditions. The control unit receives input signals and provides an electric signal corresponding to the difference between actual idle speed and optimum idle speed to the vacuum control modulator. The modulator converts the electric signal to a vacuum signal which is sent to the idle speed control actuator.

VACUUM CONTROL MODULATOR VALVE

The vacuum control modulator valve consists of a duty solenoid valve and a constant pressure valve. The duty solenoid valve produces a control vacuum, necessary to operate the idle speed control actuator, leaking the vacuum produced in the constant pressure valve. The constant pressure valve maintains intake manifold vacuum at a constant level.

IDLE SPEED CONTROL ACTUATOR

The idle speed control actuator consists of two diaphragms: a power diaphragm, displaced by the intake manifold vacuum and composite vacuum through the leak orifice and a control diaphragm, controlled by vacuum from the vacuum control modulator valve. The carburetor throttle valve is pushes open by a pushrod linked to the power diaphragm.

FAIL-SAFE SYSTEM

When any of the hoses connecting the idle speed control actuator to the vacuum control modulator is disconnected or cut off due to an accident, a ``fail-safe'' system is activated. To provide an added amount of security, two vacuum switches and two vacuum cut solenoid valves are used.
If the vacuum hose between the idle speed control actuator and vacuum control modulator is disconnected, the vacuum switches will sense atmospheric pressure and cut off electric supply to the vacuum cut solenoid valves.