7. Electric fuel pump (Fig. 1-11) Fig. 1-11 (1) Function: To deliver fuel in the oil tank to the engine with a certain oil pressure and volume, not greatly affected by temperature and voltage. (2) Structure and principle: The fuel pump consists of DC motor, vane pump, and end cap (integrating check valve, pressure release valve and anti-electromagnetic interference element), which shares the same axle and housing with the motor. The bump and motor in the housing is surrounded by gasoline, which can be used for cooling and lubricating material. The battery supplies power for the electric fuel pump through a relay.
The relay is connected with the fuel pump only when the engine starts and operates. When the engine stops due to some troubles, the fuel pump will stop automatically. The maximum pressure at the outlet of the fuel pump will be decided by the pressure release valve. As no-oil-return system is adopted, the fuel pressure regulator is installed on the fuel pump assembly. The fuel pressure regulator can adjust the pressure of the fuel pump to 380 kPa to meet the demand of the system. (3) Connection of the wiring diagram (Fig. 1-12) Notes: The temperature of the fuel greatly affects the performance of the fuel pump.
When operates under a high temperature for a long time, the pressure of the fuel pump will decrease sharply. Therefore, if the engine fails to start up after warm-up, please carefully check the fuel pump for working performance under a high temperatue. Fig. 1-12 32