Evaporative Emissions System: Description and Operation

Fig. 4 Evaporative Emission Control System:

This system, Fig. 4, prevents fuel vapors from escaping into the atmosphere by drawing the fuel vapors from the fuel tank and storing them in a charcoal canister.

When the engine is not operational, fuel vapors are absorbed into the charcoal canister. To prevent release of these vapors from the canister, a tank emissions switch (TES) closes when the ignition switch is turned off. When the engine is operating, the TES switch opens and an electronic management unit pulses a duty solenoid (TEV). The TEV meters a proper quantity of fuel vapor from the canister to the intake manifold where the vapors are mixed with the air intake charge and are burned in the combustion chambers. For inspection and testing of the fuel injected evaporative emission control system, refer to COMPUTERIZED ENGINE CONTROLS.