An improved fuel injector for providing precise control over injection timing, quantity and rate shape is provided which includes a fuel pressure balancing device for balancing the fuel pressure forces acting on a needle valve element while the element is in both the closed and open positions thereby permitting an actuator to more precisely and predictably control the movement of the needle valve element. Balance Valves The fuel pressure balancing device includes a cavity formed in the needle valve element and pressure balancing surfaces formed on the needle valve element and positioned in the cavity. Needle ValvesThe actuator may be a piezoelectric actuator for compressing actuating fluid in an actuating fluid circuit which includes a fluid chamber positioned adjacent a needle valve element and fluidically separate from a fuel supply circuit for supplying high pressure fuel for injection. Actuating fluid pressure in the chamber acts on the needle valve element to initiate injection.GATE VALVES In another embodiment, the needle valve element is directly controlled by a solenoid actuator.

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