PURPOSE: To easily detect the abnormality of a control system consisting of a fuel pressure regulator and a fuel pressure switching means, which is used to switch the fuel pressure, without adding special equipment for abnormality detection by detecting the abnormality of the system, based on the value of an air/fuel ratio as detected.
CONSTITUTION: In an engine 1, a fuel injection valve 6 is arranged at the upstream side of an intake valve 5 in an intake pipe 2. The fuel is supplied to the fuel injection valve 6 by a fuel pump 20 from a fuel tank 21 via a fuel supplying pipe 22. In addition, a fuel pressure regulator, which is used to regulate the pressure of the fuel, is connected to the fuel injection valve 6 via a fuel return valve 26. In this case, a solenoid valve 29, or a fuel pressure switching means, is arranged in a negative pressure introducing pipe 28. On the other hand, an O2 sensor 9, which is used to detect the oxygen concentration in the exhaust gas, is arranged in an exhaust pipe. Based on the values detected by the O2 sensor 9, the abnormality of a control system consisting of the fuel pressure regulator 25 and the solenoid valve 29 is detected by an ECU 40.
OTA TAKATOSHI
FUJIMOTO YUKITO
