CALIFORNIA Models
One circuit of system is connected to vacuum at the throttle port, the other at intake manifold. When the throttle plate suddenly closes, creating more than 10.6 in. Hg, the check valve closes. Vacuum pulls the throttle opener and it holds the throttle plate open. Vacuum drops slowly as the delay valve bleeds it off.
When vacuum drops too low, the check valve opens. Intake manifold vacuum is applied and controlled by vacuum regulator at 6 in. Hg. This vacuum keeps the throttle plate positioner half-open. When vehicle speed drops below 17 mph, the speed sensor turns off the solenoid valve. Manifold vacuum is cut off and the throttle closes.
A separate dashpot (not vacuum controlled) keeps the throttle from closing completely for 2-4 seconds.