The present invention relates to a method and a system for controlling a fuel pressure and more particularly to a method and a system for controlling a starter motor at an engine start of a direct fuel injection engine.
Commonly, in a conventional high pressure type direct fuel injection engine, when an engine is stopped, the fuel pressure is relieved by opening a high pressure fuel regulator in a high pressure fuel system, so as to diminish the load of the components of the fuel system for securing durability and reliability thereof.
However, when the fuel pressure is relieved at an engine stop, a vapor tends to be generated in the fuel system due to a sudden decrease in pressure of the fuel heated by a radiation from the engine, so that a defective engine starting may be caused because of a void injection at the fuel injector.
To solve the problem, for example, Japanese utility model application laid open No. 1990-127769 discloses a technique to eliminate a vapor lock by operating only the fuel pump (feed pump) without operating the starter motor for a specified time when an ignition key switch is turned on and after the specified time elapses, namely, the vapor lock is eliminated from the fuel system, the starter motor is permitted to be operated to start the engine. However, when this technique is applied to the high pressure type direct fuel injection engine, since in this type of engine the fuel is supplied from the fuel tank to the high pressure fuel system by the feed pump in the low pressure fuel system and then the the fuel is pressurized up to a specified pressure by the high pressure fuel pump in the high pressure fuel system, there is a high possibility that the fuel is not supplied enough throughout the high pressure fuel system because of the residual vapor therein in operating only the feed pump for a specified time. Especially, at a hot restarting of engine, some portion of the fuel itself supplied to the high pressure fuel system is vaporized therein by the heated distribution pipes or the high pressure fuel pump in a high temperature, and as a result of this there occurs not only a hard starting due to the vapor lock but also a scuffing or a sticking in the sliding part of the high pressure fuel pump.