Abstract: In an engine having direct fuel injection or injection at individual intake ports, the fuel injectors are of the positive displacement type and are equipped with plunger displacement sensors to yield a displacement signal representing the quantity of fuel injected. This signal is used as feedback to a closed loop PID control which compares the injected quantity to a demand quantity to determine an error and calculates a control pulsewidth which reduces the error eventually to zero. An open loop injector calibration of pulsewidth versus approximate fuel quantity is used as a base pulsewidth to which the closed loop adds a correction value.