US Patent 7216630 System and method to control spool stroke motion

An oil activated fuel injector which provides a pilot quantity of fuel prior to the main fuel injection event. A control system for a fuel injector includes a sensor for providing a signal to a control which is indicative of an opening motion of a spool. The control initiates a pull back of the spool, upon receipt of the signal, to eliminate a bounce back phenomenon of the spool during an injection of a pilot quantity of fuel. The signal may be representative of a pressure of working fluid or fuel, as well as a position or acceleration of the spool.