Evaporative Emissions System: Testing and Inspection

For the EVAP system to operate correctly, all the vapor hoses must be in good condition, have no leaks or internal restriction. Check hoses for aging and good connection at the connectors.
Check the following components as follows:

DIAPHRAGM VALVE #1 AND #2
1. Disconnect the vacuum hose at the diaphragm valve. Attach a vacuum test hose and pump to the valve.
2. Disconnect the vapor line (coming from the EVAP canister) and blow through the valve. Diaphragm valve should be closed and air stream should be blocked.
3. Apply vacuum to vacuum connection with the pump. Make sure that the diaphragm valve does not "bleed off" vacuum.
4. Blow through diaphragm valve at disconnected vapor line connector. Diaphragm valve should now be open and air stream should be unrestricted.
5. If diaphragm valve fails any of the tests above, replace and retest with new valve.
6. Disconnect the test equipment and reconnect the vacuum and vapor hose.

THERMOSTAT VALVE
1. When engine is cold (less than 58° C or 136° F), disconnect a vacuum hose at the thermostat valve. Blow through the valve. The valve should be closed and air stream should be blocked.
2. Reconnect vacuum hose and run engine to operating temperature (above 58° C or 136° F).
3. Disconnect the vacuum hose again and blow through the thermostat valve. The valve should now be open and air stream should be unrestricted.
4. If valve fails any of the tests above, replace and retest with new valve.
5. Reconnect the vacuum hose.