Evaporative Emissions System: Testing and Inspection

Fig. 4 Vacuum Connections At Throttle Body:

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:

VACUUM CONNECTION AT THROTTLE VALVE HOUSING
The vacuum hose to the throttle valve housing must be connected as shown in Fig. 4.:
1= For EVAP system
2= For pressure regulator
3= For air injection system on all vehicles except California market
4= For air injection system on California market vehicles


DIAPHRAGM VALVE
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.

EVAP SOLENOID
1. Check the electrical wires for corrosion and bad connections.
2. Disconnect the electrical connector at the EVAP solenoid.
3. Disconnect the vapor hose (coming from the EVAP canister) and blow through the valve. EVAP solenoid should be open and air stream should be unrestricted.
4. Connect a test wire from one terminal at solenoid to the ground, connect a second test wire from the other terminal to a 12V positive connection.
5. Blow through EVAP solenoid at disconnected vapor line connector. Solenoid should be closed and air stream should be blocked.
6. Disconnect and connect the ground test leed at solenoid terminal. Do this several times in a short period. The solenoid should "click" every time you connect or disconnect the wire.
7. If EVAP solenoid fails any of the tests above, replace and retest with new solenoid.
8. Disconnect the test leeds and reconnect the vapor hose and electrical connector.

ELECTRONIC CONTROL UNIT
The electronic control unit (ECU) controls the EVAP solenoid. For ECU testing procedures see "COMPUTERIZED ENGINE CONTROLS".