This disclosure provides a fuel injector system and method in which the timing of events in during period of fuel injection of a piezoelectric-actuated fuel injector are estimated based on sensed forces within the injector. The force sensor is positioned between a piezoelectric actuator and a hydraulic link assembly mechanically coupled with the piezoelectric actuator, and the force sensor operable to output a signal corresponding to forces between the piezoelectric actuator and the hydraulic link assembly. From information contained in the sensor output signal, timing in the injection period of at least one fueling characteristic based can be estimated to allow for adjusting fuel injector characteristics to compensate for variations affecting fuel injection, such as manufacturing tolerances, environmental conditions, and deterioration/wear.