Abstract: An advance arrangement controls timing of fuel delivery by a fuel pump for use in an engine. The advance arrangement includes an advance piston, a servo piston, a light load piston, and an arrangement. The advance piston is slidable within a first bore and cooperates, in use, with a cam arrangement of a fuel pump to adjust the timing of fuel delivery by the pump. A surface associated with the advance piston is exposed to fuel pressure within a first control chamber. The servo piston is slidable within a further bore provided in the advance piston to control the pressure of fuel within the first control chamber. The servo piston is responsive to speed dependent fuel pressure variations within a servo control chamber, thereby to permit adjustment of the timing in response to engine speed. The light load piston is moveable relative to the advance piston against the action of a light load control spring in response to fuel pressure variations within a light load control chamber.

Abstract: An advance arrangement controls timing of fuel delivery by a fuel pump for use in an engine. The advance arrangement includes an advance piston, a servo piston, a light load piston, and an arrangement. The advance piston is slidable within a first bore and cooperates, in use, with a cam arrangement of a fuel pump to adjust the timing of fuel delivery by the pump. A surface associated with the advance piston is exposed to fuel pressure within a first control chamber. The servo piston is slidable within a further bore provided in the advance piston to control the pressure of fuel within the first control chamber. The servo piston is responsive to speed dependent fuel pressure variations within a servo control chamber, thereby to permit adjustment of the timing in response to engine speed. The light load piston is moveable relative to the advance piston against the action of a light load control spring in response to fuel pressure variations within a light load control chamber.