via the bore 37 into the chamber 9 and inlet outlet 9 a it ensures that the flow rate of the hydraulic pump i is zero and therefore that the diaphragms are motionless and do not have any pressurized suction or delivery effect on fuel to the injectors the fuel flow rate towards the injectors is therefore also zero when under the effect of the control rod 38 the liners 34 are in the position represented in fig3 the bores 36 are obstructed by the liners and the flow rate of the hydraulic pump i is at its maximum it ensures that the fuel flow rate to the injectors is also at maximum between these two extreme positions all the intermediate flow rates can be obtained as a function of the position of the liners 34 the position being determined by the position of the rod 38 which is controlled by the running of the engine by any appropriate monitoring means it ensures that the output rate of the pump i is regulated as a function of the fuel flow rate required for the injection and that surplus fuel reflux to the reservoir is kept as low as possible it should be noted however that the fuel flow rate thus obtained is a pulsated rate in fact if for instance the liners 34 are in a position such that only 10 of the maximum rate of the pump i is being supplied into the part 13 a of the volume 13 this means that the pump i does not have any output during 90 of the stroke of each piston or that there is only an output during 10 of the stroke of each piston the flow rate is thus effectively a pulsated flow rate to this end a device.