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Emissions Management Evaporative Emissions: The control of the evaporative fuel vapors (Hydrocarbons) from the fuel tank is important for the overall reduction in vehicle emissions. The evaporative system has been combined with the ventilation of the fuel tank, which allows the tank to breath (equalization). The overall operation provides: VAPORS TO EVAPORATIVE EMISSION VALVE DM-TL FILTER • An inlet vent, to an otherwise "sealed" fuel tank, for the entry of air to replace the fuel consumed during engine operation. 13410095.eps • An outlet vent with a storage canister to "trap and hold" fuel vapors that are produced by the expansion/evaporation of fuel in the tank, when the vehicle is stationary. The canister is then "purged" using the engine vacuum to draw the fuel vapors into the combustion chamber. This "cleans" the canister allowing for additional storage. Like any other form of combustible fuel, the introduction of these vapors on a running engine must be controlled. The ECM controls the Evaporative Emission Valve which regulates purging of evaporative vapors. ON-BOARD REFUELING VAPOR RECOVERY (ORVR) The ORVR system recovers and stores hydrocarbon fuel vapor that was previously released during refueling. Non ORVR vehicles vent fuel vapors from the tank venting line back to the filler neck and in many states reclaimed by a vacuum receiver on the filling station’s fuel pump nozzle. When refueling, the pressure of the fuel entering the tank forces the hydrocarbon vapors through the tank vent line to the liquid/ vapor separator, through the rollover valve and into the charcoal canister. The HC is stored in the charcoal canister, and the system can then “breath” through the DM TL and the air filter. 62 MS S54 Emissions Management
Liquid/Vapor Separator: Fuel vapors are routed from the fuel tank filler neck through a hose to the Liquid/Vapor Separator (located in the right rear wheel well behind the trim). The vapors cool when exiting the fuel tank, the condensates separate and drain back to the fuel tank through a return hose (1). The remaining vapors exit the Liquid/ Vapor Separator to the Active Carbon Canister. 134100143.eps Active Carbon Canister: As the fuel vapors enter the canister, they will be absorbed by the active carbon. The remaining air will be vented to the atmosphere through the end of the canister (passing through the DMTL and filter) allowing the fuel tank to “breath”. When the engine is running, the canister is then "purged" using intake manifold vacuum to draw fresh air through the canister which extracts the hydrocarbon vapors into the combustion chamber. This cleans the canister for additional storage. The Active Carbon Canister is located under the luggage compartment floor with the DM TL Pump. 134100147.eps Evaporative Emission Valve: This ECM controlled solenoid valve (located under the intake manifold) regulates the purge flow from the Active Carbon Canister through the idle air distribution pipe into the intake manifold . The ECM Relay provides operating voltage, and the ECM controls the valve by regulating the ground circuit. The valve is powered open and closed by an internal spring. 134100101.eps MS S54 FROM EVAPORATIVE EMISSION CANISTER ECM RELAY If the Evaporative Emission Valve circuit is defective, a fault code will be set and the “Malfunction Indicator Light” will be illuminated. If the valve is “mechanically” defective, a driveability complaint could be encountered and a mixture related fault code will be set. 134100100.eps 63 MS S54 Emissions Management
Page 1: Table of Contents Subject Page MS S
Page 5 and 6: Exhaust Emissions: The combustion p
Page 7 and 8: If the exhaust has a lower oxygen c
Page 9 and 10: Misfire Detection: As part of the O
Page 11 and 12: • Fuel Tank Capacity must be betw
Page 13 and 14: Evaporative Emission Purging is reg
Page 15 and 16: Catalyst Monitoring is performed by
Page 17 and 18: Secondary Air Injection is required
Page 19 and 20: The Integrated Ambient Barometric P
Page 21 and 22: Workshop Hints Before any service w
Page 23 and 24: This Special Tool Set #90 88 6 161
Page 25 and 26: Cruise Control: As with other elect
Page 27 and 28: Workshop Hints IMPORTANT! From Dece

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