Evaporative Emissions System: Testing and Inspection

VAPOR CANISTER:

a. Poor idle, stalling and poor driveability can be caused by:

- Damaged canister.
- Hoses split, cracked and or, not connected to the proper tubes.

b. Evidence of fuel loss or fuel vapor odor can be caused by:

- Liquid fuel leaking from the fuel lines.
- Cracked or damaged vapor canister.
- Disconnected, misrouted, kinked, deteriorated or damaged vapor pipe, or canister hoses.

VISUAL CHECK OF VAPOR CANISTER:

- Replace vapor canister if cracked or damaged.
- Replace vapor canister if fuel is leaking from bottom and check operation of the entire system.

FUNCTIONAL TESTS:

Apply a short length of hose to the lower tube of the purge valve, and attempt to blow air through it. Little or NO air should pass into the canister. A small amount of air will pass if the canister has a constant purge hole.

With a hand vacuum pump apply vacuum (15" Hg) to the control vacuum tube (upper tube). If the diaphragm does NOT hold vacuum for at least 20 seconds, the diaphragm is leaking and the canister must be replaced.

If the diaphragm holds vacuum, try to blow through the hose connected to the lower tube while vacuum is still being applied. An increased flow of air should be observed. If not, the canister must be replaced.

THERMOSTATIC VACUUM SWITCH:

With the engine coolant temperature below 38~C (100~F), apply vacuum to the manifold side of the switch. Switch should hold a vacuum.

Raise the temperature of the engine to above 50~C (122~F). Vacuum should drop off.

If valve fails either test, Replace it.

CANISTER PURGE SOLENOID:

On vehicles with some California Emissions or Tier 1, the TVS is replaced by a control module controlled canister purge solenoid to cycle operation of the canister. For diagnosis of the canister purge solenoid, Testing and Inspection