Evaporative Emissions System: Testing and Inspection

Fig. 117 Testing the purge control valve:

SYSTEM TESTING

1. Disconnect the black vacuum hose from the intake manifold nipple and plug the nipple. Connect a hand vacuum pump to the disconnected black vacuum hose, Fig. 117.
2. While the engine is cold [engine coolant temperature less than 50 degrees C (122 degrees F)] apply 53 kPa (15 in. Hg) of vacuum and verify that vacuum is held from idle to 2,500 rpm.
3. After the engine is warmed up [engine coolant temperature greater than 50 degrees C (122 degrees F)] apply 53 kPa (15 in. Hg) of vacuum and verify that vacuum is held at idle and leaks at 2,500 rpm.

Fig. 115 Testing the bowl vent valve:

BOWL VENT VALVE

CAUTION!

Check the bowl vent valve after the engine has been allowed to cool. If the engine is hot fuel can gush out of the BVV nipple.

1. Remove the air cleaner.
2. Disconnect the bowl vapor hose from the bowl vent valve (BVV) nipple and connect a hand vacuum pump to the BVV nipple, Fig. 115.
3. Apply a vacuum of 20 kPa (6.0 in. Hg) to the BVV and verify that when the engine is running at idle the BVV holds vacuum and leaks when the engine is stopped.

Overfill Limiter (Two Way Valve):

OVERFILL LIMITER VALVE

Remove the overfill limiter valve and blow gently through both ends. Air should pass through the valve in both directions with slight resistance.

Fig. 118 Testing the purge control valve:

PURGE CONTROL VALVE

1. Remove the purge control valve.
2. Connect a hand vacuum pump to the vacuum nipple of the purge control valve, Fig. 118.
3. Apply 53 kPa (15 in. Hg) of vacuum and verify that air will pass through the the purge control valve.
4. Verify that no air will pass through the the PCV when no vacuum is applied.

Fig. 119 Testing the thermo valve:

THERMO VALVE

1. Disconnect the vacuum hose (white stripe) from the thermo valve and connect a hand vacuum pump to the thermo valve, Fig. 119.
2. Apply a vacuum to the thermo valve and verify that when coolant temperature is less than 10 degrees C (50 degrees F) vacuum leaks and when coolant temperature exceeds 25 degrees C (77 degrees F) vacuum holds.
3. Disconnect all vacuum hoses from the thermo valve (be sure to mark the hoses to facilitate reconnecting them).

Fig. 120 Testing the thermo valve:

THERMO VALVE

4. Connect a hand vacuum pump to nipples (B), (C), and (D), Fig. 120. Apply vacuum and verify that when engine coolant temperature is less than 40 degrees C (104 degrees F) vacuum leaks and when engine coolant temperature is greater than 80 degrees C (176 degrees F) vacuum holds.

Note: If the thermo valve fails and must be replaced use 3M locking sealant 4171 or equivalent and torque the thermo valve to 20 to 40 Nm (15-30 ft. lbs.). Do not use wrenches or pliers on the resin part of the valve during installation.