A method is disclosed for controlling an injector of a combustion engine. The injector comprises an injection valve housing with an injection valve cavity, a valve needle being axially movable within the injection valve cavity, a valve seat, on which the valve needle rests in a closed position and from which the valve needle is lifted for an open position, a spring element being designed and arranged to exert a preload force (PF) on the valve needle acting to urge the valve needle in the closed position. A calibration value (CV) is provided, which is representative for the preload force (PF). A base quantity (BOT) is provided correlated to the fluid volume to be dispensed by the injector. Dependent on the calibration value (CV) and the base quantity (BOT), a set-point opening time length (SOT) is determined. The valve needle of the injector is controlled to be in the opening position correlated to the set-point opening time length (SOT).