The working principle of the high-pressure oil pump:
1. The fuel transfer pump pumps fuel from the fuel tank, passes through a filter with an oil-water separator, and enters the high-pressure pump through the inlet pipe.
2. The fuel delivery pump allows fuel to pass through the orifice of the pressure relief valve and enter the lubrication and cooling circuit of the high-pressure pump. The camshaft causes the plungers of the three pumps to move up and down according to the contour of the cams.
3. If the oil supply pressure exceeds the opening pressure of the pressure relief valve, the fuel delivery pump can allow the fuel to enter the plunger chamber through the high-pressure pump inlet valve. The plunger of the high-pressure pump is moving downwards (suction stroke), and when the plunger passes through the dead center, the inlet valve closes.
When the common rail pressure is reached, the compressed fuel enters the high-pressure cycle (oil circuit). The plunger continues to supply fuel until it reaches the top dead center (supply stroke), and the pressure decreases, causing the outlet valve to close. The fuel pressure still in the plunger chamber also decreases, and the plunger (pump plug) moves downward again.
As long as the pressure in the plunger cavity drops below the supply pressure of the fuel pump, the inlet valve opens again and the pumping process begins again
