Evaporative Emissions System: Testing and Inspection

Evaporative Emission Control System Schematic:

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

^ Inoperative purge valve

^ Damaged canister

^ Hoses split, cracked and/or not connected to the proper tubes.

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

^ Liquid fuel leaking from fuel lines

^ Inoperative purge valve

^ Disconnected, misrouted, kinked, deteriorated or damaged vapor hoses or control hoses

Replace a cracked or damaged canister. If fuel is leaking from bottom of canister, replace it and check hoses for incorrect routing, restrictions or leaks.

Connect a length of hose to the lower tube of the purge valve and attempt to blow 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 orifice). With a hand vacuum pump, apply vacuum of 51 kPa (15" Hg) through the control valve tube (upper tube). If the diaphragm holds vacuum, again 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.

Check filter at bottom of canister. Replace if dirty, plugged or damaged.