With Upgraded Emissions

EVAP Purge System Metro W/ Upgraded Emissions:

An evaporative emission control system is used to prevent the emission of fuel vapors into the atmosphere. The vapors generated in the fuel tank pass through Tank Pressure Control (TPC) valve and enter the charcoal canister. The charcoal absorbs and stores the fuel vapors until throttle body vacuum is applied to the canister purge control valve. The valve will not open until the the engine coolant has reached operating temperature and the throttle valve is opened past the idle position. The fuel vapors in the canister are then drawn into the intake manifold through the purge control valve and purge line. At the same time, fresh air is drawn through the filter at the bottom of the canister, purging the charcoal of the fuel vapors.

Only when the following conditions are satisfied, will the Engine Control Module (ECM) open the vacuum passage of the EVAP solenoid purge (SP) valve.

^ Engine coolant temperature is high (normal operating temperature).

^ Engine speed is higher than specified.

^ Throttle valve opening is not in the idle position.

^ Engine running within specified load.

2-Way Check Valve:

The TPC valve is mounted on or near the fuel tank in the fuel vapor line. The check valves main purpose is to equalize the pressure in the fuel tank. When the pressure in the fuel tank becomes positive and reaches its specified value, it opens the valve to let the vapor into the charcoal canister. When the pressure in the fuel tank becomes negative and reaches its specified value, it opens the valve to let the air flow into the fuel tank.