Determining a drift in the fuel static flow rate of a piezoelectric injector of a motor vehicle heat engine

A method for determining a drift in the static fuel flow rate of a piezoelectric injector of a motor vehicle combustion engine, said injector comprising an electrohydraulic valve of the servo valve type designed to cause the injector to open or to close, said method comprising the following steps, executed by a control unit when the injector is open and the electrohydraulic valve is closed:

• a) acquiring at least two pressure values P1 and P2, measured by a pressure sensor in a supply chamber of the injector at at least two respectively associated different instants t1 and t2;
• b) calculating, from the acquired pressure values and the respectively associated instants, a gradient of pressure with respect to time dP;
• c) calculating a measured static flow rate Qmes of which the value is equal to the gradient of pressure with respect to time dP multiplied by a first determined value Vsys corresponding to the total volume of the fuel pressurized and divided by a second determined value K corresponding to the elastic modulus of the fuel;
• and
• d) determining a value representative of the drift in the static flow rate Qratio, which value is proportional to the ratio of the measured static flow rate Qmes to a third determined value Qnominal corresponding to the nominal flow rate of the injector within the range of pressure values of the gradient of pressure with respect to time dP, and storing, in a memory of the control unit, an information item representative of the drift in the static flow rate which information item is associated with said value representative of the drift in the static flow rate.