Evaporative Emissions System: Testing and Inspection

Evaporative Emission Control System:

NOTE: The engine coolant temperature must be below 63°C (145°F).

1. Disconnect the #19 vacuum hose at the purge control valve and connect a vacuum gauge to the hose.

Evaporative Emissions System Testing:

2. With the engine running at idle, there should be no vacuum.
3. If vacuum is available:
a. Check the routing of vacuum hose #19, and correct as necessary.
b. If the vacuum hose routing is correct, check the purge cut-off solenoid valve (see COMPUTERIZED ENGINE CONTROLS).
4. If no vacuum is available, perform next test.
5. Start the engine and warm it up to normal operating temperature.

NOTE: The engine should be at its normal operating temperature (the cooling fan should cycle on and off at least once).

6. Block the rear wheels and set the parking brake. Raise the front of the car and support with jack stands.

Evaporative Emissions System Testing:

7. Place the shifter in second gear (automatic and manual transmissions).
8. Raise the engine speed to 3500 rpm. Vacuum should be available. If vacuum is not available, check the purge cut-off solenoid valve.
If vacuum is available, disconnect the vacuum gauge and re-connect the hose to the charcoal canister.
9. Remove the fuel tank filler cap.
10. Remove the charcoal canister purge air hose from the frame and connect the hose to a vacuum gauge.
11. Raise the engine speed to 3500 rpm. Vacuum should be available within one minute.
a. If no vacuum is available, remove the charcoal canister and inspect for signs of damage. Replace canister as necessary.
b. If vacuum is available within one minute, and/or no damage to the canister is found, perform next test.

Fig. 66 Checking Vacuum At The Purge Fitting:

12. With the engine OFF, disconnect the hose from the charcoal canister PCV fitting, and remove the fuel tank filler cap.
13. Connect a vacuum pump to the charcoal canister ("PURGE") fitting and apply vacuum. The purge valve should hold vacuum. If vacuum drops, replace the charcoal canister, and re-test.
14. Start the engine and reconnect the hose to the charcoal canister PCV fitting [keeping vacuum applied to the ("PURGE") fitting].
- On Federal vehicles raise the engine speed to 3500 rpm (in 2nd gear)
- On California cars test at idle.
"PURGE" side vacuum should drop to zero when hose is connected.
If "PURGE" side vacuum does not drop to zero, replace the canister and retest.

Fig. 67 Testing Function Of The "Tank" Fitting:

15. Connect a vacuum pump to the ("TANK") fitting and apply vacuum. The valve should not hold vacuum.
a. If the valve does not hold vacuum, re-install the fuel filler cap and re-connect all hoses; test is complete.
b. If the valve holds vacuum, replace the charcoal canister and re-test.

Two Way Valve Testing:

16. Remove the fuel tank filler cap.
17. Remove the vapor line from the fuel tank and connect a "T" fitting for a vacuum gauge and vacuum pump as shown in.
18. Slowly apply vacuum while observing the vacuum gauge. Vacuum should stabilize momentarily at 5 to 15 mbar (0.2 to 0.6 in. Hg). If vacuum stabilizes (valve opens) below 5 mbar (0.2 in. Hg) or above 15 mbar (0.6 in. Hg), replace the valve and re-test.

Two Way Valve Testing:

19. Move the vacuum pump hose from the vacuum to the pressure fitting.
20. Slowly pressurize the vapor line while watching the gauge. The pressure should stabilize at 10 to 35 mbar (0.4 to 1.4 in Hg).
a. If the pressure momentarily stabilizes (valve opens) at 10 to 35 mbar (0.4 to 1.4 in Hg), the valve is OK.
b. If the valve stabilizes above or below the specified pressure, replace the valve and re-test.
21. For further testing of the EVAP system, see COMPUTERIZED ENGINE CONTROLS.