An improved r.p.m. regulator of a fuel injection pump for internal combustion engines includes an improved control spring mechanism. The control spring mechanism is connected to one end of a control lever which in turn is connected at its other end to a fuel supply quantity setting member. The control lever serves to actuate the fuel supply quantity setting member in accordance with the forces applied to the control lever by the control spring mechanism and an r.p.m.-dependent force applying structure which applies a force to the control lever in opposition to the force applied by the control spring mechanism. The control spring mechanism in one embodiment of the invention includes axially aligned tandem springs mounted between the control lever and a setting lever, a first connecting member and a second connecting member. In another embodiment of the invention a single spring is mounted between the control lever and a setting lever and tandem springs are mounted adjacent to one end of the second connecting member in a perforated pot that is associated with the control lever.