METHOD OF OPERATING A FUEL INJECTION SYSTEM

A method of controlling fuel injection in an internal combustion engine having at least one cylinder with an associated fuel injector for performing injector events, wherein for each injector event a drive signal is generated to cause an opening of the fuel injector to spray fuel in accordance with a demand fuel quantity. In a drive mode, the drive signal has a length, PWf, that corresponds to a reference length, PWref, determined from a reference map, MAP-PWref, of demand fuel quantity vs. pulse length, and corrected by a correction value, PWcorr. PWcorr is determined based on a map, MAP-PWcorr, depending on demand fuel quantity, the map MAP-PWcorr being learned during engine runtime and representing a difference between a learned, injector-specific hydraulic open time and a reference hydraulic open time.