Functional description of leakage diagnosis
The evaporative emissions system (including fuel tank) is equipped with a leakage diagnosis which can detect leaks.
The diagnosis is based on the overpressure procedure and is supposed to show leaks which are larger than 1 mm in diameter.
The Leak Detection Pump (LDP V144 builds up an overpressure of about 30 mbars in the EVAP canister during the diagnostic process. The pump is turned off when the pressure is attained. If the pressure drops below a specified value, the pump is turned on again. The On Board Diagnosis supervises the switching intervals and enters a code into Diagnostic Trouble Code (DTC) memory if the intervals are too short.
- Hose connections are fastened with spring band clips and collar bands.
- In principle, replace collar bands with spring band clips.
- The Hose clip pliers VAG 1921 are recommended for spring band clips.
Review safety measures, refer to Safety precautions when working on the fuel supply system .
Maintain cleanliness, refer to Rules for cleanliness .
Overview diagram of the evaporative emissions system, refer to Evaporative emissions system, diagram .