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