Emission Control Systems: Testing and Inspection

Fig. 16 Disconnecting vacuum line:

Anti-Afterburn Valve No. 1
1. Run engine until it reaches normal operating temperature and ensure engine operates smoothly at idle, then shut off engine.
2. Disconnect air hose between air control valve and air pump at air pump.
3. Disconnect electrical connectors from relief solenoid valve and switching solenoid valve.
4. Start engine and run at idle, then block off air hose and ensure air is not drawn into air hose and idling speed does not change.
5. Disconnect vacuum line from vacuum pipe, Fig. 16, and ensure idle speed drops but returns to normal as soon as vacuum line is reconnected to vacuum pipe.
6. Connect all hoses and electrical connectors to proper locations.

Anti-Afterburn Valve No. 2
1. Run engine until it reaches normal operating temperature.
2. Disconnect air hose between No. 2 anti-afterburn valve and air cleaner at air cleaner and ensure air is not drawn into hose.
3. Disconnect vacuum line from No. 2 anti-afterburn valve and ensure air is not drawn into air hose.
4. Connect vacuum line and ensure air is drawn into air hose for a few seconds.
5. If air is drawn for more than three seconds or not drawn at all replace valve.
6. Connect all hoses to proper locations.

Dash Pot
1. Remove air cleaner.
2. Ensure dashpot rod does not prevent throttle lever from returning to idle stop.
3. Operate throttle lever fully and ensure dashpot rod extends quickly. Release throttle lever and ensure throttle lever returns slowly to idle position after it has contacted the dashpot rod.
4. Connect a suitable tachometer to the engine.
5. Operate engine until normal operating temperature is obtained. Ensure engine is operating at specified idle speed. Operate throttle lever until it is no longer contacting the dashpot rod.
6. Slowly decrease engine speed and check engine speed at which the throttle lever contacts the dashpot rod. Engine speed should be 3800---4200 RPM on carbureted engine, or 2350---2650 RPM on fuel injected engine. If engine speed is not within specification, loosen locknut and adjust engine speed by turning dashpot diaphragm.