Vehicles with engine code AZZ, BKJ, BMV and BRJ
Above the surface of the fuel in the tank, depending on the pressure and ambient temperature, fuel vapors are formed to a greater or lesser extent.
The activated carbon absorber system keeps these hydrocarbon vapors out of the atmosphere.
Fuel vapors come from the highest point of the fuel tank (at the filler neck) through the expansion tank into the activated charcoal absorber.
Activated charcoal absorbs these gases like a sponge.
While driving with active lambda control (the engine is warm) Solenoid valve 1 for the N80 activated charcoal filter is controlled by the engine control unit depending on load and speed. The opening time depends on the incoming signals.
During the cleaning process (activated carbon regeneration) Vacuum in the intake manifold sucks in clean air through the canister vent. The fuel vapors and clean air contained in the activated carbon at a certain point in time are dosed and then burned in the engine.
In the absence of power (e.g. an open circuit) the solenoid valve 1 of the N80 activated charcoal filter is closed. In this case, the absorber is not emptied.
NOTE: Hose connections are secured with spring and clamp clamps.
Clamp clamps should always be replaced with spring clamps.
Vehicles with engine code BAA and BMX
Above the surface of the fuel in the tank, depending on the pressure and ambient temperature, fuel vapors are formed to a greater or lesser extent.
The activated carbon absorber system keeps these hydrocarbon vapors out of the atmosphere.
Fuel vapors come from the highest point of the fuel tank (at the filler neck) through the expansion tank into the activated charcoal absorber.
Activated charcoal absorbs these gases like a sponge.
While driving with active lambda control (warm engine) Activated charcoal filter solenoid valve 1 N80 and Activated charcoal filter solenoid valve 2 N115 are controlled depending on load and speed by the engine control unit. The opening time depends on the incoming signals.
During the cleaning process (activated carbon regeneration) Vacuum in the intake manifold sucks in clean air through the canister vent. The fuel vapors and clean air contained in the activated carbon at a certain point in time are dosed and then burned in the engine.
In the absence of power (for example, a break in the electrical circuit) absorber system solenoid valves are closed. In this case, the absorber is not emptied.
Descriptions of the operating principle of the leak detection system
Absorber system (including fuel tank) equipped with a leak diagnostic system that recognizes leaks in the system.
The diagnosis is based on the overpressure principle and should indicate leaks larger than 1 mm in diameter.
During the diagnosis, an overpressure of approx. 30 mbar is generated in the canister system via the fuel system diagnostic pump V144. When the set pressure is reached, the pump switches off. If the pressure falls below a certain value, the pump is switched on again. The self-diagnosis system monitors the frequency of switching on the pump and, if the intervals are too short, stores an error in the fault memory.
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