Leak Detector: Testing and Inspection

CANISTER
For evaporation monitoring, there are a DM-TL (Diagnosis Module for Tank-Leakage), and an air filter as the illustration.

1. Look for loose connections, sharp bends or damage to the fuel vapor lines.




2. Look for distortion, cracks or fuel leakage.




3. After removing the EVAP Canister, inspect for cracks or damage.

Diagnosis Module For Tank Leakage (DM-TL)










PRINCIPLE OF OPERATION
The diagnosis module comprises an electromechanically driven 1-overpressure pump together with a 2-change-over valve with integrated 3-reference restriction. In the change-over valve's setting "a" as shown, the pump delivers through the reference restriction. In the other setting the pump delivers through the 4-canister into the fuel-tank system. The engine-management system measures the pump's electrical current consumption in each setting. A comparison of the currents is a measure for the leakage in the tank. If the electrical current consumption is identical in both settings, this means that there is a tank-system leak which is equal to the reference restriction. In order to make the procedure independent of environmental influences and tolerances in the overpressure pump, the system performs a comparison with a reference restriction. Outside of the leakage-diagnosis mode, the change-over valve remains in the "a" setting. The canister can be regenerated via a large flow cross-section, and only an insignificant pressure loss occurs. This is advantageous above all on vehicles with high canister-regeneration rates.