Measuring check motion through pressure sensing

A fuel injector comprising:

• a lower outer body;
• a tip having an outer surface and an inner surface forming a bore;
• an at least one orifice disposed within said tip and being open at said inner and outer surfaces;
• a fuel passage disposed in said tip and in fluid communication with said at least one orifice;
• a needle valve with a first surface, a second surface and being disposed within said bore, said needle valve being moveable between a first position at which fluid communication between said orifice and said fuel passage is blocked and a second position at which fluid communication between said orifice and said fuel passage is open;
• a fuel chamber disposed in said tip;
• a pressure control cavity disposed in said lower body adapted to receive a pressurized fluid;
• said needle valve having said first surface open to said pressure control cavity, said needle valve being fluidly biased towards said first position by pressurized fluid acting on said first surface and being fluidly biased towards said second position by pressurized fluid acting on said second surface;
• and
• a sensor disposed in said lower body and being adapted to measure a pressure within said pressure control cavity.