When the accelerator is pressed and the throttle valve opens, the control cam in the fuel injection pump is moved along its axis at the same time. The control cam is also rotated on its axis as a function of the inlet manifold pressure generated by the turbo supercharger. These two movements determine the amount of fuel injected. The inlet manifold pressure acts upon the control piston in the pressure regulator, which is linked, to a rack in the injection pump. A pinion moves along this rack thus rotating the control cam. The position of the control piston depends upon the pressure below and above the piston.