Fuel-delivery and variable-volume retraction valve assembly for fuel-injection system

A fuel-delivery valve assembly (70) with a variable-volume, fuel-retraction collar (96) is operatively mounted in a bore (72) of an engine-driven high-pressure fuel pump rotor (62) fed with fuel through a metering valve (46). The valve assembly operates at speeds proportional to engine speed between an open position, in which a pressure wave of fuel generated by the fuel pump (66) is transmitted to a fuel injector nozzle (22), and a closed position, in which a valve charging chamber (90) is sealed by the retraction collar (96) which has a pair of flats (116,118) ground therein. During low-speed engine operations, the flats (116,118) provide bleed paths to reduce the volume of fuel retracted so that engine shut-down will be immediate when the metering valve (46) is closed. During high-speed operation, valve element operating frequency increases to such a rate that the flats (116,118) are ineffective as bleeds and the volume of fuel retracted is increased. With increased retraction of fuel, secondary fuel injection is eliminated.