The pumping and distributing rotor revolves, and is aTaxi. The transfer pressure, therefore, is controlled by abalance between the regulating spring pressure and therequirements of the injection pump at any moment. As the engine speed increases, the transfer pressure rises,moving the piston against the pressure of the regulatingspring to progressively uncover the regulating port in the valve sleeve and allow a metered flow of fuel to by-pass back to the inlet side of the transfer pump. When the injection pump is in operation fuel at transferpressure enters the lower end of the valve sleeve, forcingthe ‘free’ piston upwards against the regulating spring. Thepriming port is connected by a passage in the end plateto the delivery side of the transfer pump, thus enablingthe fuel to by-pass the stationary transfer pump andprime the injection pump. When priming the injection pump, fuelat lift pump pressure enters the central port in theregulatingvalve sleeve and moves the ‘free’piston against the pressure of the piston retaining spring to uncover thepriming port in the lower end of the valve sleeve. Ca.3, itwill be seen that the valve is cylindrical and containsa small ‘free’ piston, the travel of which is limited bytwo light springs.

The pressure regulating valve, in addition to regulatingthe pressure of the fuel from the transfer pump, also provides a means of by-passing the transfer pump whenpriming the injection pump. Mounted on the outer end of the pumping anddistributing rotor is a sliding-vane-type transfer pump.This pump raises the fuel pressure to an intermediatelevel, and as its capacity is many times the maximumrequirements of the injection pump a regulating valve,housed in the pump end plate, allows excess fuel to beby-passed back to the suction side of the transfer pump. To ensure correct location, transmits the drive from the chain wheel to the injection pump drive hub.Ī central rotating member forms the pumping anddistributing rotor, and this is driven by the drive hubthrough a splined drive shaft on which is mounted the governor flyweight assembly. THE FUEL SYSTEM (Distributor-type Injection Pump) Caįuel injection pump air bleed points 1.

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