Distributor Vacuum Vent Valve: Testing
- Connect vacuum gauge to body port (distributor source) with engine warmed up enough to open any ported vacuum switches or thermal vacuum switches in the system. Accelerate engine to fast idle and hold. Vacuum should show a gradual increase. Return engine to idle and gauge should register zero within a few seconds. If not, replace valve.
- If checking valve with direct manifold vacuum to vacuum signal port, gauge should register steady vacuum at idle and zero vacuum when hose is disconnected at manifold source. If not, replace vacuum vent valve.NOTE: Some engines also incorporate a fuel-vacuum separator in distributor vacuum lines to prevent fuel from migrating to the distributor vacuum motor. It may also be used on amplified EGR systems to prevent fuel from reaching the vacuum amplifier.