PURPOSE: To prevent breakege of an engine and economize fuel by detecting the abnormal rise of the supercharged pressure in comparison with the set value judging from the intake air amount and the number of revolution of the engine, and forcing fuel feeding to be stopped.

CONSTITUTION: The intake air amount Qa is metered by an air float 1, and the number N of engine revolution is measured by an ignition coil 2, and each signal is sent to a control unit 4, and the fuel pressurized to a fixed level is supplied to an engine intake passage 11 by means of an injection valve 3 in compliance with the driving signal from the control unit 4. The control unit 4 compares the intake air amount Qa input with the maximum intake air amount QaMAX corresponding to the predetermined maximum supercharged pressure PBMAX by means of a discriminating circuit A, and when the intake air amoutn Qa is larger, the pulse from an injection valve 3 is controlled, to stop fuel feeding, and breakage of the engine due to the abnormal increase of the supercharged pressure is prevented.