Advance arrangement

摘要

An advance arrangement for controlling the timing of fuel delivery by a fuel pump for use in an engine. The advance arrangement comprises an advance piston (12) which is slidable within a first bore (14) and which co-operates, 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 (12) being exposed to fuel pressure within a first control chamber (38), and a light load piston (26) movable relative to the advance piston (12) against the action of a light load control spring (28) in response to load dependent fuel pressure variations within a light load control chamber (60), thereby to adjust the timing under light load conditions. The light load piston (26) includes first and second parts (26a, 26b) which are movable relative to one another so as to permit adjustment of the extent of travel of the light load piston.