Evaporative Emissions System: Testing and Inspection

Fig. 101 Evaporative Emission Control System Hose Routing:

COLD ENGINE TEST (Coolant temp. below 64°C/147°F)

1. Check the vacuum lines for proper connections, cracks, blockages, etc, Fig. 101.

Fig. 102 Checking For Vacuum To The Purge Control Valve:

2. Disconnect the #3 hose at the purge control diaphragm valve (on top of the charcoal canister), and connect a vacuum gauge to the hose, Fig. 102.
3. Start the engine and allow it to idle. No vacuum should be available at the #3 hose.
4. If vacuum is available, test the purge cut-off solenoid valve.

Fig. 103 Checking For Vacuum To The Purge Control Valve:

HOT ENGINE TEST (Coolant temp. above 64°C/147°F)

1. Disconnect the #3 hose at the purge control diaphragm valve (on top of the charcoal canister), and connect a vacuum gauge to the hose, Fig. 103.
2. Warm the engine up to normal operating temperature (cooling fan should cycle ON and OFF at least once). Vacuum should be available at idle. If vacuum is not available, check the purge cut-off solenoid valve.
3. Disconnect the vacuum gauge and re-connect the hose.
4. Remove the fuel filler cap.

Fig. 104 Checking Air Flow Through Charcoal Canister:

5. Remove the purge air hose from the frame and connect the hose to a vacuum gauge, Fig. 104.
6. Raise the engine speed to 3500 rpm. Vacuum should show on the gauge within 1 minute. If vacuum is OK, test is complete.
7. If no vacuum is available, remove the charcoal canister and inspect for signs of damage and replace as necessary.

Fig. 105 Applying Vacuum To Purge Valve:

8. Stop the engine and disconnect the upper vacuum hose from the charcoal canister "PCV" fitting, Fig. 105.
9. Connect a vacuum pump to the charcoal canister "purge" fitting and apply vacuum. The canister valve should hold vacuum. If the vacuum drops, replacd the charcoal canister and retest.
10. Re-connect the hose to the canister "PCV" fitting and restart the engine. Purge side vacuum should drop to zero. If vacuum does not drop, replace the charcoal canister and retest.
11. Remove all test equipment, re-connect all hoses, and replace the fuel filler cap.