in line 31 corresponding to the length of the start up procedure the air mass measuring signal from the respective sensor 11 does not operate in the first place for sustaining the load and fuel is metered to the combustion engine independently of the load at the time preferably the ratio of resistance of the two resistors 25 and 26 is chosen in such a way that the voltage at the coupling point 17 does not rise at all or only insignificantly as compared with the operation at idle even when the initial signal of the air mass meter 11 increases because of higher air content fig3 shows a circuit arrangement which permits the placing of a predetermined voltage at coupling point 17 for this purpose this coupling point 17 is included in an in series arrangement of two resistors 35 and 36 as well as a diode 35 between resistor 36 and transistor 34 while the base of the transistor 34 corresponding to the switch 20 shown in fig1 again receives a signal from the start up switch 18 the base of the transistor 33 is connected via a first resistor 38 with the positive line 28 and via a further resistor 39 with the connecting point between diode 37 and transistor 34 with this arrangement a constant potential.