Fuel pump assembly

A fuel pump assembly for an internal combustion engine, the fuel pump assembly comprising:

• a plunger arranged to reciprocate under the influence of a drive assembly driven by means of a drive shaft, to perform a pumping cycle comprising a pumping stroke and a return stroke, the pumping stroke comprising movement of the plunger from a bottom dead centre (BDC) position to a top dead centre (TDC) position to pressurise fuel within a pump chamber, and the return stroke comprising movement of the plunger from the TDC position to the BDC position,
• a spring assembly including a return spring configured to apply a return force to the plunger to effect the return stroke, wherein the return spring is cooperable, at a first end, with a first member coupled to the plunger and movable at a first speed dependent on the speed of rotation of the drive shaft and, at a second end, with a second member which is movable at a damped speed relative to the first speed so that the return spring has a variable stroke length depending on the speed of rotation of the drive shaft;
• and a damper arrangement which acts on the second member to set the damped speed, wherein the damper arrangement includes a damper chamber for receiving a fluid which applies a damping force to the return spring, wherein a clearance gap is defined between the second member and a wall of the damper chamber to allow the fluid to flow out of the damper chamber.