Combination Air By-Pass/Air Control Valve
- Disconnect hoses from outlets "A" and "B". See Fig 1. Disconnect and plug vacuum line to port "D". With engine operating at 1500 RPM, airflow should come out of by-pass vents.
- Reconnect vacuum line to port "D". Disconnect and plug vacuum line to port "S". Ensure vacuum is present in line to vacuum port "D". Accelerate engine speed to 1500 RPM. Airflow should come out of outlet "B". Airflow should not be detected at outlet "A".
- Apply 8-10 in. Hg vacuum to port "S". With engine operating at 1500 RPM, airflow should come out of outlet "A". If valve is bleed-type, less air will flow from outlet "A" or "B" and main discharge will change when vacuum is applied to port "S".
- If conditions in previous steps are not met, replace valve. If above conditions are met, valve is okay. Reconnect hoses and vacuum lines.