Fuel injection pumps

A fuel injection pump has a rotary and axially slidable distributor member housed in a sleeve in which is formed a series of outlet ports and a series of inlet ports the two series of parts being in axially spaced planes. The distributor member has an outlet groove for registration with the outlet ports in turn and an inlet groove for registration in turn with the inlet ports. The two grooves communicate with a pumping plunger bore so that as the distributor member rotates fuel will be supplied to the bore through an inlet port and the inlet groove and will flow from the bore through the outlet groove and an outlet port. Interconnected balancing grooves are provided on the distributor member for communication with the outlet ports and inlet ports respectively to ensure that following delivery of fuel through an outlet port, that port will be connected to an inlet port before the next delivery of fuel through the port takes place.