One-way vacuum valve installed in the vacuum hose. The arrow indicates the direction of the hose installation hose (to the vacuum amplifier).
PERFORMANCE ORDER
1. Loosen the hose clamps and remove the vacuum hose from the unilateral vacuum valve.
2. Create a vacuum with a hose end, attached to the engine. Air should pass. When air passes through the tube in either direction or does not flow, the valve is defective and the hose should be replaced.