Fuel pump

A fuel pump, comprising:

• a pump housing having a first lifter bore, a fuel inlet aperture, a fuel bypass aperture, and a crankcase chamber, the first lifter bore communicating with the crankcase chamber;
• a first roller lifter being disposed in the first lifter bore;
• the first roller lifter being operably coupled to a first pumping plunger;
• a camshaft having a drive cam disposed in the crankcase chamber, the drive cam contacting the first roller lifter, the camshaft being rotatable by an exterior motive force so as to rotate the drive cam to thereby reciprocate the first roller lifter within the first lifter bore;
• the fuel inlet aperture extending through a portion of the pump housing to the crankcase chamber and being adapted to receive fuel therethrough;
• the fuel bypass aperture communicating with the fuel inlet aperture above the crankcase chamber;
• the fuel inlet aperture supplying a first portion of the fuel which has not traversed through the crankcase chamber after entering the fuel inlet aperture to the fuel bypass aperture, the fuel bypass aperture routing the first portion of the fuel to a fuel volume control valve, the fuel volume control valve supplying a portion of the first portion of the fuel to the first pumping plunger;
• the pump housing having a first pin aperture extending through the pump housing to the first lifter bore;
• and
• a first anti-rotation pin extending through the first pin aperture and into an elongated aperture of the first roller lifter to prevent rotation of the first roller lifter.