A fuel control system for an engine includes a control module that includes a fuel rail pressure module and a comparison module. The fuel rail pressure module determines a first fuel rail pressure of a fuel rail after a first event and a second fuel rail pressure of the fuel rail after a second event. The first event includes N conditions, a first of the N conditions comprises deactivation of a fuel pump of the engine, and N is an integer. The second event includes M conditions, a first of the M conditions comprises activation of a fuel injector, and M is an integer. The comparison module adjusts a fuel injector constant of the fuel injector based on the first fuel rail pressure, the second fuel rail pressure, and an injector activation period corresponding to the second event.