Patent ID: 6941932

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 which is slidable within a first bore 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 being exposed to fuel pressure within a first control chamber; a servo piston which 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 being responsive to speed dependent fuel pressure variations within a servo control chamber, thereby to permit adjustment of the timing in response to engine speed; a light load piston 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; an adjuster to permit adjustment of the extent of travel of at least one of the light load piston and the servo piston; and an arrangement for ensuring the servo piston is substantially unresponsive to speed dependent fuel pressure variations within the servo control chamber, in circumstances in which fuel pressure within the light load control chamber is increased beyond a predetermined amount.