Injector apparatus

An injector apparatus for injecting fluid under pressure into an associated chamber, the apparatus comprising:

• a body;
• a first piston moveable in the body, the first piston defining a first working area facing the associated chamber and movement of the first piston is selectively controllable by controlling the fluid in the control chamber, wherein the control chamber is partially defined by a wall of the body;
• a high pressure piston defining a high pressure working area facing a high pressure chamber;
• the first working area being greater than the high pressure working area, the first piston being operable to compress fluid in the high pressure chamber using the high pressure piston;
• the first piston further defining an injector orifice through which the fluid can be injected into the associated chamber from the high pressure chamber and defining a valve seat;
• a valve member selectively operable to engage the valve seat to operably isolate the high pressure chamber from the injector orifice and selectively operable to disengage the valve seat to fluidly connect the high pressure chamber with the injector orifice, the valve member partially received within said wall of the body, and wherein the valve member is in sliding engagement with the wall of the body.