Air By-Pass Valve (Normally Closed)
- Disconnect air supply hose at valve outlet. See Fig 1. Remove vacuum line from vacuum nipple. Ensure vacuum exists at vacuum line before proceeding.
- Reconnect vacuum line to vacuum nipple. With engine speed at 1500 RPM, air pump supply air should be heard and felt at air by-pass valve outlet.
- With engine speed still at 1500 RPM, disconnect vacuum line. Air at outlet should decrease significantly or shut off. Air pump supply air should now be heard or felt at silencer ports or at dump port.
- If normally closed air by-pass valve does not perform as described in steps 2) and 3), check air pump for faults. If air pump is operating satisfactorily, replace air by-pass valve.