Evaporative Emissions System: Testing and Inspection

Fig.63 - Purge Control Valves:

NOTE: If engine will not start, proceed to step 1. If it does start and run, proceed to step 2.

PROCEDURE
1. Disconnect purge line, Fig. 63, from purge control valve and plug line, then attempt to start engine. If engine does not start, the problem is not in the evaporative control system.

2. With engine idling, disconnect vacuum signal line, Fig. 63, from purge control valve and plug hose, then remove valve from canister. If a strong hissing sound is heard at purge control valve, replace valve.


NOTE: A slight hissing sound is normal due to small orifice in valve.


3. Reconnect vacuum signal line, Fig. 63, to purge control valve which remains separated from canister, then accelerate engine to about 2000 rpm so that ported vacuum is applied to purge control valve. If strong hissing sound is heard at purge control valve, system is performing properly. Proceed to step 4. If not, check for vacuum at source port, and operation of PVS valve, PCV valve, and retard delay valve(s). Repair or replace components as necessary.

4. Return engine to idle. Strong hissing sound at purge control valve should stop if there is a port vacuum signal at valve. If strong hissing sound does not stop, check for vacuum at source port and check operation of retard delay valve(s). Repair or replace components as necessary.

5. Reconnect purge control valve to canister.


NOTE: Make sure that carburetor fuel bowl vent line has a continuous downward slope to the carbon canister.