FUEL INJECTION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE

In a fuel injection control system for an internal combustion engine provided with a low pressure fuel pump (1) and a high pressure fuel pump (2), a feed pressure is made as low as possible, while suppressing generation of vapor. Proportional plus integral control of the high pressure fuel pump (2) is carried out so as to make the pressure of fuel come close to a target value between the high pressure fuel pump (2) and fuel injection valves (7), wherein in cases where the high pressure fuel pump (2) is in operation, the feed pressure, which is a pressure of fuel between the low pressure fuel pump (1) and the high pressure fuel pump (2), is caused to go down when an integral term in the proportional plus integral control does not change or is decreasing, and the feed pressure is caused to go up when the integral term is increasing. On the other hand, in cases where the high pressure fuel pump (2) is in a stopped state, the feed pressure is made higher than before the high pressure fuel pump (2) is stopped.