Fuel injection system and fuel pump

A fuel injection system (100) for an internal combustion engine is disclosed. The fuel injection system comprises at least one electronically-controlled fuel injector (102), a fuel pump (104) for supplying pressurised fuel to the or each injector (102), and a controller (130) arranged to control the injection of fuel from the or each injector (102). The fuel pump (104) comprises a pump chamber (146), a pumping element (140), and a drive mechanism (360) for driving the pumping element (140) in a pumping stroke in which the volume of the pump chamber (146) is reduced, and a filling stroke in which the volume of the pump chamber (146) is increased and in which fuel is admitted to the pump chamber (146) from a fuel source (116). The drive mechanism (360) comprises a biasing arrangement (468) arranged to apply a resilient biasing force, such as a spring force, to the pumping element (140) to drive the pumping stroke. In this way, the resilient biasing force acts to pressurise the fuel for injection, providing a simplified fuel injection system with electronic control of the injection timing and duration. Fuel pumps suitable for use in such a system are also disclosed.