EVAPORATIVE EMISSIONS CONTROL SYSTEMSChapter 8Classroom Manual Page 244Lab Manual Page 328CBCAUTOMOTIVERK

OBJECTIVESDescribe the operation of an evaporative (EVAP) control system during the canister purge and non purge modes.Diagnose & service evaporative systems.Use scan tester to diagnose EVAP systems.Diagnose EVAP system thermal vacuum valvesCBCAUTOMOTIVERK

EVAP SYSTEMSGasoline (Hydrogen and Carbon) HC is a pollutant and must not be allowed to escape to the atmosphere.Purpose of EVAP is to contain vapors from fuel tank and carburetor when engine is off.Burn vapors in engine when warm and under cruise conditions.CBCAUTOMOTIVERK

SYSTEM DESIGNSMain components are the charcoal canister, purge valve, rollover valve, lines.Two types of EVAP systemsMechanical - Vacuum controlledComputerized - Electrically controlledCBCAUTOMOTIVERK

CHARCOAL CANISTERTypical canister in vapor storage mode.Absorbs vapors from carburetor and fuel tankCBCAUTOMOTIVERK246C

PURGE VALVESFord Purge valves.Typically normally closedPurges above idleCBCAUTOMOTIVERK245C

ROLLOVER VALVELocated in top of the fuel tank.CBCAUTOMOTIVERK245C

OBD II Evaporative Emission System MonitorTests ability of fuel tank to hold pressureTests ability of purge system to vent vapors from charcoal canisterDetects leaks and restrictions is EVAP systemFuel tank will cause MIL light to come on.

Thats all Folks!