are below the operating temperature of the internal combustion engine however the bimetallic spring 50 acts on the spring support cup 49 in opposition to the spring 46 with the effect that the closing force transmitted to the diaphragm 45 is reduced however immediately after starting the electric heater 53 heats up the bimetallic spring 50 and as a consequence the force exerted by the bimetallic spring 50 on the spring support cup 49 is also reduced the desired basic tension setting of the bimetallic spring 50 can be obtained simply by pressing the bolt 51 into the housing of the pressure control valve 42 to a variable predetermined depth thus when the internal combustion engine is suddenly accelerated during its warm up phase in order to provide in addition to the fuel quantity metered out by the metering and quantity distribution valve assembly 10 in dependence on the aspirated air quantity an additional acceleration fuel quantity so as to produce a richer fuel air mixture then according to the present invention the pressure of the pressurized fuel in the control pressure circuit 37 is reduced a reduction of the pressure of the pressure fluid in the control pressure circuit 37 reduces the restoring force acting on the measuring member 2 so that even though the air quantity flowing past the measuring member 2 remains the same there is a greater excursion of the measuring member 2 and hence of the control slide 14 which in turn increases the fuel quantity metered out by the annular groove 27 and the control slits 30 of the metering valve assembly 10 the reduction of the pressure of the pressurized fluid in the pressure control circuit 37 is produced by the servo assembly 61 fig2 which.