Liquid fuel injection pumping apparatus

A liquid fuel injection pumping apparatus for supplying fuel to internal combustion engines, the apparatus comprising an injection pump adapted to be driven in timed relationship with an associated engine, fluid pressure operable means for effecting adjustment of a component of the injection pump, a feed pump for supplying fuel to the injection pump during the filling periods thereof, a throttle valve for controlling the amount of fuel supplied to the injection pump, a relief valve including a valve member movable by the outlet pressure of the feed pump to an open position in which fuel is spilled from the outlet of the feed pump, resilient means acting to urge the valve member to a closed position, means for generating a first pressure which is lower than the outlet pressure of the feed pump, but which varies in accordance with the speed at which the injection pump is driven, conduit means through which said first pressure is applied to said valve member to assist the action of the resilient means whereby the outlet pressure of the feed pump has a value higher than said first pressure, a further conduit interconnecting the outlet of the feed pump and said means whereby flow of fuel will occur along said further conduit due to the difference in pressure between the ends thereof, a pair of restrictors in said further conduit, a branch conduit extending from intermediate said restrictors, and through which the pressure intermediate said restrictors is transmitted to said fluid pressure operable means, with the size of one of said restrictors being adjustable in accordance with the setting of the throttle valve whereby the fluid pressure applied to said fluid pressure operable means will depend both upon the speed at which the injection pump is driven, and also upon the setting of the throttle valve.