Method for detecting leaks in a motor vehicle tank ventilation system

A method for detecting leaks in a motor vehicle tank ventilation system including a fuel tank, an adsorption filter in communication with said fuel tank via a ventilation conduit, a differential pressure sensor arranged in the ventilation conduit, an air supply conduit connecting said adsorption filter with the atmosphere and having a shut-off valve arranged therein, a discharge conduit connecting said adsorption filter to an induction pipe of an internal combustion engine and including a controllable regeneration valve, and a control unit for controlling the valves, said differential pressure sensor being connected to said control unit for relating thereto the pressure sensed in said ventilation conduit, said method comprising the steps of:

• closing said shut-off valve so as to isolate said system from the atmosphere, opening said regeneration valve to provide for communication between said engine induction pipe in which a vacuum is maintained during engine operation, and said adsorption filter and controlling said regeneration valve to reduce the pressure in the tank ventilation system so as to generate in said system a predetermined vacuum, maintaining said predetermined vacuum for a predetermined control period after which a stable equilibrium state of the air/fuel vapor ratio in the system is achieved, then closing said regeneration valve to isolate said system also from said induction pipe, monitoring the vacuum in said system over a predetermined period and indicating the existence of a leak in the tank ventilation system if the vacuum in said system falls below a predetermined threshold value during said predetermined period.

A method for detecting leaks in a motor vehicle tank ventilation system including a fuel tank, an adsorption filter in communication with said fuel tank via a ventilation conduit, a differential pressure sensor arranged in the ventilation conduit, an air supply conduit connecting said adsorption filter with the atmosphere and having a shut-off valve arranged therein, a discharge conduit connecting said adsorption filter to an induction pipe of an internal combustion engine and including a controllable regeneration valve, and a control unit for controlling the valves, said differential pressure sensor being connected to said control unit for relating thereto the pressure sensed in said ventilation conduit, said method comprising the steps of:

• closing said shut-off valve so as to isolate said system from the atmosphere, opening said regeneration valve while the air/fuel vapor ratio changes so as to provide in said system a reduction of pressure to achieve a vacuum that is greater than a predetermined vacuum, and controlling said regeneration valve over a predetermined control period, after which a stable equilibrium state of the air/fuel vapor ratio in the system is achieved, so as to maintain the pressure in said system, such that the vacuum is reduced from the initial value to the predetermined vacuum within said predetermined control period, then closing said regeneration valve to isolate said system also from said induction pipe, monitoring the vacuum in said system over a predetermined period and indicating the existence of a leak in the tank ventilation system if the vacuum in said system falls below a predetermined threshold value during said predetermined period.