Trapped Vacuum Spark

When engine temperature is below pre-set specified value, manifold vacuum signal is routed through check valve to distributor. Ports on TVS are blocked. Check valve will keep distributor vacuum at levels higher than manifold depression during vehicle acceleration.

Small sintered iron bleed orifice is provided in check valve to allow for leak-down to enable engine to be restarted if it stalls. This applies to all models except Light Duty California and High Altitude emissions, 5.7L V8 with Heavy Duty emissions, and all 7.4L V8 engines.

When engine temperature is above pre-set value, TVS ports will be open to allow manifold vacuum to distributor. During this mode of operation, check valve will act as a connector.