Evaporative Emissions System: Testing and Inspection

TESTING AND INSPECTION

Carbon Canister

There are no moving parts or nothing to wear in the canister. Check for loose, missing, cracked, or broken connections and parts.

Fig. 53 Testing purge control valves:

Purge Control Valve

1. Apply vacuum to port B, Fig. 53. If there is vacuum flow, replace valve.
2. Apply and maintain 16 inches Hg vacuum to port A, then apply vacuum to port B. If air does not flow, replace valve. Never apply vacuum to port(s) C.

Fig. 54 Testing ported vacuum switches:

Ported Vacuum Switches

1. With engine cold, ensure that passage A to B is closed and passage A to C is open, Fig. 54.
2. Start engine and run until it reaches normal operating temperature, then ensure that passage A to B is open and passage A to C is closed. On 4-port valve, check A1 to B1 and A2 to B2 separately.
3. If valve does not operate as described, replace valve.

Solenoid Vent Valve

Apply 9---14 volts DC to valve. If valve does not close, replace valve.

Thermal Vent Valve

Ensure that valve is fully closed when valve temperature is 90° F or below and that valve is fully open when valve temperature is 120° F or above.

Vacuum Bowl Vent Valve

1. Ensure that air flows between carburetor port and canister port when no vacuum is applied to vacuum signal nipple.
2. Apply vacuum to vacuum signal nipple and ensure that air does not flow between carburetor port and canister port.

Vacuum/Thermostatic Bowl Vent Valve

1. With valve temperature at or above 120° F, ensure that air flows between carburetor port and canister port when no vacuum is applied to vacuum signal nipple.
2. With valve temperature at or above 120° F, apply vacuum to vacuum signal nipple and ensure that air does not flow between carburetor port and canister port.
3. With valve temperature at or below 90° F, ensure that there is no or very little air flow between carburetor port and canister port, whether or not vacuum is applied to vacuum signal nipple.