LEMON Manuals: Even more car manuals for everyone
Home >> Porsche >> 1997 >> Boxster Standard >> Repair and Diagnosis >> Engine Performance >> System >> DME 5.2.2 Diagnosis >> Function of Tank Ventilation Diagnosis

Function of Tank Ventilation Diagnosis

In order to check the system for leaks, vacuum is built up in the tank, the system sealed and a test performed to see how quickly the vacuum diminishes again. Pressure conditions are influenced by the vaporization of fuel. Therefore, prior to diagnosis the pressure increase due to fuel vaporization is examined.

Tank ventilation diagnosis is divided into three steps:

  1. Measuring the pressure increase due to fuel vaporization.
    • The EVAP canister purge valve (1) and shutoff valve (6) are closed. The increase in pressure is measured by the tank pressure sensor (5).
  2. Vacuum buildup in the system.
    • The EVAP canister purge valve is opened and the shutoff valve remains closed. This causes vacuum to build up in the tank. If no vacuum builds up, a large leak is present, e.g. the tank cap is not screwed on.
  3. Vacuum reduction in the system.
    • At a particular vacuum (approx. 8 mbar), the EVAP canister purge valve is closed once more. The system is now sealed. Depending upon the speed at which vacuum is reduced, leaks in the system may be determined.
scientia non olet · About LEMON Manuals