The fuel pressure regulator is responsible for adjusting the fuel pressure according to the change of the engine load, so that the fuel pressure (related to the air-fuel ratio) matches the engine load. When the load is small, the vacuum of the engine intake system is high, the diaphragm is sucked up, and a small amount of fuel returns to the fuel tank through the return pipe. Under heavy load, the vacuum of the engine intake system is low, the regulator diaphragm closes the return pipe, and the pressure in the fuel pipe remains unchanged. Because the working temperature of the engine is 1000C, which is much higher than the evaporation temperature of gasoline at 70 ℃, in order to reduce the harmful gas HC produced by the evaporation of fuel in the fuel tank, and also to avoid the gas resistance caused by the reduction of the pressure in the fuel pipeline during idling in hot weather and small load, which leads to difficult starting and unstable operation, in recent years, new models have controlled the fuel return during small load.

1. Install a solenoid valve on the vacuum pipe between the fuel pressure regulator and the engine intake system. When the engine temperature reaches 100 ℃, close the vacuum pipe and stop the small load oil return.

2. To cancel the return pipe on the fuel pressure regulator is to cancel the fuel pressure regulator.

3. The fuel pressure regulator is no longer installed. In addition to the air flow sensor, the intake manifold absolute pressure sensor is also installed in the engine intake system. The injection pulse width is adjusted according to the change of engine load, and the injection pulse width is used to replace the fuel pressure adjustment, so as to effectively reduce the HC produced by fuel evaporation in the fuel tank, At the same time, it can avoid the air lock when the pressure in the fuel pipe is reduced in hot weather and small load, and improve the emission and the working stability of the engine.

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