A fuel pump assembly comprises a plunger arranged to reciprocate within a plunger bore via 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, and the return stroke comprising movement of the plunger from the TDC position to the BDC position. The fuel pump assembly comprises a spring assembly including a return spring that 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.

In a hybrid fuel supply system for the same high pressure supply pump used for gasoline direct injection (DI) is also used to supply the port injection (PI) system. For a given pumping stroke, fuel can be delivered only to the DI system, only to the PI system, or a first portion can be delivered to the DI system and a second portion delivered to the PI system. The pumping chamber always fills to maximum volume. Fuel metering for DI is by a control valve, which when closed delivers fuel into the DI system and when opened spills pumped fuel into the PI system. Any spill at high pressure opens a pressure regulating valve in the PI system that dumps fuel at excess pressure to a low pressure region to maintain the PI system at a constant target pressure.

A fuel pump assembly comprises a plunger arranged to reciprocate within a plunger bore via 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, and the return stroke comprising movement of the plunger from the TDC position to the BDC position. The fuel pump assembly comprises a spring assembly including a return spring that 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.

In a hybrid fuel supply system for the same high pressure supply pump used for gasoline direct injection (DI) is also used to supply the port injection (PI) system. For a given pumping stroke, fuel can be delivered only to the DI system, only to the PI system, or a first portion can be delivered to the DI system and a second portion delivered to the PI system. The pumping chamber always fills to maximum volume. Fuel metering for DI is by a control valve, which when closed delivers fuel into the DI system and when opened spills pumped fuel into the PI system. Any spill at high pressure opens a pressure regulating valve in the PI system that dumps fuel at excess pressure to a low pressure region to maintain the PI system at a constant target pressure.