Evaporative Emissions System: Description and Operation

EVAP Canister System

Function of leak diagnostic

The EVAP canister system (incl. fuel tank) is equipped with a leak diagnostic that detects leaks (improper seal) in the system.

The diagnostic is based on pressure characteristics and is intended to detect leaks with diameters greater than 1 mm.

During the diagnostic, the Leak Detection Pump (LDP) -V144- generates a positive pressure of approx. 30 m bar in the EVAP canister system. The pump is switched off once the pressure is reached. If pressure falls below a specified value, the pump is switched on again. On Board Diagnostic monitors the switch intervals and stores a DTC in DTC memory if the intervals are too short.

NOTE:
- Hose connections are secured with screw-type clamps, spring-type clamps or tensioning clamps.
- Always replace tensioning clamps with spring-type clamps or screw-type clamps.
- Fuel hoses at engine must only be secured with spring-type clamps. The use of clamping collars or screw clamps is not permitted.







- VAS 5024A spring clip installation tool is recommended for installing spring-type clips.
- Components marked with * are tested via On Board Diagnostic (OBD), Diagnostic mode 3: Check DTC memory.

- Observe safety precautions. Safety Precautions When Working on Fuel Supply System
- Observe rules for cleanliness. [1][2]Technician Safety Information
- Removing and installing parts of the EVAP canister system.

Overview plan of EVAP canister system:
- Vehicles with engine code AEG, AVH, AZG.
- Vehicles with engine code BDC.
- EVAP canister system, checking for proper seal.