Patent ID: 7350508

Claim:
An advance arrangement for use in controlling timing of fuel delivery by a fuel pump for use in an engine comprising; an advance piston ( 12 ) which is slidable within a first bore ( 14 ) and which 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 ( 12 ) being exposed to fuel pressure within a first control chamber ( 38 ) and the advance piston ( 12 ) being slidable within the first bore ( 14 ) in either an advance or a retard direction to advance or retard, respectively, the timing of the fuel pump delivery, a servo piston ( 24 ) which is slidable within a further bore ( 22 ) provided in the advance piston ( 12 ) to control the pressure of fuel within the first control chamber ( 38 ), the servo piston ( 24 ) being responsive to speed dependent fuel pressure variations within a servo control chamber ( 37 ), thereby to permit adjustment of the timing in response to engine speed, and a light load piston ( 26 ) moveable relative to the advance piston ( 12 ) against the action of a light load control spring ( 28 ) in response to fuel pressure variations within a light load control chamber ( 60 ), wherein the light load piston ( 26 ) is carried within a cold cranking sleeve ( 120 ), the cold cranking sleeve ( 120 ) being slidable within the first bore ( 14 ) against the action of a cold cranking control spring ( 128 ) in response to fuel pressure variations within a cold cranking control chamber ( 134 ) such that the cranking control spring ( 128 ) acts, in use, to slide the cold cranking sleeve ( 120 ) a predetermined distance in the advance direction and fuel pressure variations within the control chamber ( 134 ) serve to slide the cold cranking sleeve ( 120 ) back in the retard direction.