Evaporative Emissions System: BMW: Description
BMW evaporative control system consists of a purge system leading from fuel tank to hose of crankcase ventilation system. Located between fuel tank and crankcase ventilation system is a vapor storage tank and an activated charcoal canister.
Fuel evaporation emissions are prevented from entering atmosphere by means of a sealed filler cap on fuel tank. Fuel tank has no direct vent to atmosphere. An excess fuel return valve is also used and is located in fuel supply line. A fuel return line connects this valve to fuel tank.