Except Vanagon
- Remove hose leading to canister from control valve. Blow into valve. Check that air flow is blocked and that air does not leak from valve seams.
- Remove hose from control valve's vacuum advance port. Remove vacuum retard hose from distributor. Connect it to control valve's vacuum advance port. Remove hoses from other 2 valve ports.
- Start engine. Blow air into valve's canister port. Check that air flow is blocked and that air does not leak from valve seams. If valve performs incorrectly in either test, replace valve.