Fuel system for an internal combustion engine

A fuel system for an internal combustion engine of the type in which fuel is injected into a combustion space of the engine, the system comprising an injection nozzle positioned on the engine so that fuel delivered to the nozzle will be injected into the combustion space, an injection pump for delivering fuel to the nozzle in timed relationship with the associated engine, said pump comprising a piston movable in a bore to vary the size of a pumping chamber, resilient means biasing the piston in a direction to increase the size of the pumping chamber, electromagnetic means operable to move the piston against the action of the resilient means to displace fuel from the pumping chamber through the associated nozzle, a valve controlled fuel inlet to said pumping chamber and through which fuel can flow into the bore from a source of fuel when the piston is moved by the action of the resilient means, the system including first electronic means for supplying power to the electromagnetic means when delivery of fuel by the pump is required, second electronic means for providing a first control signal to said first electronic means when it is desired to energize the electromagnetic means, third electronic means for providing a second control signal to said first electronic means to cut off the supply of power to said electromagnetic means thereby to allow fuel to flow into the pumping chamber, said third electronic means being operative to determine from signals supplied to it, the time required for the pumping chamber to fill with the desired quantity of fuel thereby to determine the instant the second control signal is supplied, fourth electronic means for determining the desired amount of fuel to be supplied to the engine and fifth electronic means for determining the desired timing of delivery of fuel, the signals provided by said fourth and fifth electronic means being supplied to said third electronic means, and said fifth electronic means comprising a store in which is stored information regarding the required timing of delivery of fuel for different engine speeds and load, said fifth electronic means receiving a signal from said fourth electronic means and also a signal indicative of the speed of the associated engine.