Fuel injection system and timing advance device therefor

Abstract

A hydraulic advance device for selectively transmitting applied forces to a fuel injector of an internal combustion engine. The device is operative to select a normal or advanced timing of the fuel injection. An outer cylindrical body (66) is mounted in the upper end of a fuel injector adapter. An inner body (108) is slidably received in an outer body and a pressure responsive plunger (104) is slidably received in a bore formed in the inner body and defines in cooperation therewith a fluid chamber (128). A one-way valve (132) in the chamber permits fluid above a predetermined pressure applied during the advanced stage of the fuel injection cycle to enter the chamber which prevents movement of the plunger relative to the inner body member. At pressures below a predetermined value and during the normal phase of the fuel injection cycle, the plunger first moves relative to the inner body a predetermined amount during which time no movement is transferred to the inner body thus delaying fuel injection relative to advance phase fuel injection.