IMPROVED PRESSURE DROP ANALYSIS STRATEGY

A method of operating a fuel injection system of an internal combustion engine comprising at least one fuel injector associated with a combustion chamber and coupled to a fuel rail comprising a pressure sensor. The method comprises applying to the injector a drive signal of predetermined length; and a pressure drop analysis, PDA, strategy is operated, by which an injected fuel quantity corresponding to a given injection event is determined from a mapping based on a rail pressure drop corresponding to the given injection event. Rail pressure data are acquired by the pressure sensor during an analysis window encompassing the given injection event. In the method, the rail pressure data are processed in order to cancel predetermined artefacts of known intensity and timing due to the injection system and intervening in the analysis window, whereby corrected pressure data are obtained; and the PDA strategy is operated based on a pressure drop calculated from the corrected rail pressure data.