Trapped Vacuum Spark

When engine temperature is less than pre-set value, manifold vacuum signal is routed through check valve to distributor. Ports on TVS are blocked. Check valve will keep distributor advance vacuum at levels higher than manifold vacuum 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.

When engine temperature is greater than pre-set value, TVS ports will be open to allow manifold vacuum to distributor advance canister.