Disclosed is a method for discharging the pressure in a fuel supply rail of an injection system of an engine, the fuel injection rail connected to a fuel tank by piezo-electric injectors, each including a needle and a piezo-electric actuator pressing on a servo valve of the injector. The injection system includes a fuel pressure sensor and an electrical generator transmitting electric current pulses to each actuator. When the accelerator is released, a first electrical command allows determination of a moment of opening of the respective servo valve without triggering an injection. A second electrical command triggers a discharge of fuel from the fuel supply rail to the tank and therefore to discharge the pressure of the supply rail without triggering an injection. The second electrical command charges the piezo-electric actuator between a first voltage level that opens the servo valve, and a second voltage level triggering an injection.

Disclosed is a method for limiting fuel leakage from at least one injector in an engine of a motor vehicle, the engine being stopped and the motor vehicle ignition circuit being switched off, the injector being supplied with fuel via a fuel rail which is pressurized during operation, the pressurization persisting for a certain period when the engine has been stopped and the ignition circuit switched off, leading to leakage of fuel through the injector. The injection rail is subjected to forced cooling following the stoppage of the engine with the motor vehicle ignition circuit switched off, which is sufficient to reduce the pressure, the forced cooling continuing until the pressure in the rail is close to atmospheric pressure.

A method for managing the mass of fuel injected into the cylinder of an internal combustion engine fed by direct injection. The pressure and the pressure drop per unit of time are monitored (13) during the starting phase. If the pressure becomes too low (7), or if it drops too quickly (9), the mass of fuel injected on each cycle is adjusted (15) in order to maintain a high fuel pressure in the injector (37). The method can be applied, for example, in the event of low-temperature starting using any type of fuel, for example pure or mixed ethanol.

Methods and systems are provided for adjusting operation of fuel injectors of an internal combustion engine to reduce injector ticking noise during direct injection fuel rail pressure release. The method includes first reducing a significant part of the direct injection fuel rail pressure via a mechanical high pressure pump relief valve and only if further pressure relief is required then intermittently activating the direct injector to inject in small amount of fuel. Due to the reduced frequency of activation and small pulse-widths, the impact force transmitted from injectors to cylinder head is small thereby reducing the objectionable ticking noise.

An apparatus and method for operating a fuel injector of an internal combustion engine is disclosed. A first energizing electrical current is supplied to an injector solenoid, causing the opening of an injector control volume and a pressure reduction in said injector control volume, for a first energizing time. The first energizing time is predetermined to avoid that the pressure in the injector control volume approximates a value which would cause an injector needle to raise up and a fuel injection to start. After the predetermined time interval, a second energizing electrical current is supplied to the injector solenoid for a predetermined second energizing time, which is a function of a rail pressure (p.sub.rail) and a fuel injection quantity.

Methods and systems, using a controller (20), for performing fuel pressure control operation of an engine (12) having at least one cylinder (16) is disclosed. The controller (20) includes a fuel system control unit (42) configured to control a fuel pressure applied to at least one injector (18) of the engine (12) during a motoring condition period (412) based on a commanded pulse train duration (410). During the motoring condition period (412), no combustion occurs in the at least one cylinder (16) of the engine (12). The commanded pulse train duration is a time period during which the at least one injector (18) of the engine (12) is activated for a drain operation. The fuel system control unit (42) is configured to command the at least one injector (18), for the commanded pulse train duration during the motoring condition period (412), to release fuel from the at least one injector (18) without injecting the fuel into the at least one cylinder (16) of the engine (12).

Disclosed is a method for discharging the pressure in a fuel supply rail of an injection system of an engine, the fuel injection rail connected to a fuel tank by piezo-electric injectors, each including a needle and a piezo-electric actuator pressing on a servo valve of the injector. The injection system includes a fuel pressure sensor and an electrical generator transmitting electric current pulses to each actuator. When the accelerator is released, a first electrical command allows determination of a moment of opening of the respective servo valve without triggering an injection. A second electrical command triggers a discharge of fuel from the fuel supply rail to the tank and therefore to discharge the pressure of the supply rail without triggering an injection. The second electrical command charges the piezo-electric actuator between a first voltage level that opens the servo valve, and a second voltage level triggering an injection.

A method of operating a fuel injection system for a motor vehicle includes one or more of the following: operating a fuel injector to perform a fuel injection, the fuel injector being in fluid communication with a fuel rail; sampling a rail pressure in the fuel rail during the fuel injection; regulating the rail pressure at a desired injection pressure, P.sub.inj, to the fuel injector; measuring an overall leakage on variations of the rail pressure across an engine cycle for the motor vehicle and between two engine positions of an internal combustion engine for the motor vehicle; and restarting a new measurement cycle for a new pressure measurement target.

A method for controlling a fuel injector of an engine system includes applying a pull-in current to close a spill valve of the fuel injector and detecting a timing at which the spill valve closes. The method also includes adjusting at least one of an amplitude of the pull-in current, a duration of the pull-in current, or a timing of a start of an application of the pull-in current based on the detected timing of the closing of the spill valve.

Methods and systems, using a controller (20), for performing fuel pressure control operation of an engine (12) having at least one cylinder (16) is disclosed. The controller (20) includes a fuel system control unit (42) configured to control a fuel pressure applied to at least one injector (18) of the engine (12) during a motoring condition period (412) based on a commanded pulse train duration (410). During the motoring condition period (412), no combustion occurs in the at least one cylinder (16) of the engine (12). The commanded pulse train duration is a time period during which the at least one injector (18) of the engine (12) is activated for a drain operation. The fuel system control unit (42) is configured to command the at least one injector (18), for the commanded pulse train duration during the motoring condition period (412), to release fuel from the at least one injector (18) without injecting the fuel into the at least one cylinder (16) of the engine (12).