Control method

A method of controlling the timing of fuel injection in a fuelling system for a diesel engine fuel system including a fuel injector supplied with fuel from a source of fuel arranged to supply fuel to the injector over a range of pressures within a high pressure fuel range, the method comprising:

• varying a drive current which is supplied to the fuel injector at a first time so as to initiate or terminate a primary injection of fuel;
• monitoring the pressure of fuel within the source so as to detect when a variation in fuel pressure occurs;
• calculating a time delay between the first time and a second, later time at which a variation in fuel pressure within the source is detected, and
• using the measured time delay to adjust the time at which the drive current is varied so as to initiate or terminate a subsequent injection of fuel, thereby to ensure initiation or termination of the subsequent injection of fuel occurs at a required time.