Why do you often use a manual oil pump to pump oil?

At present, diesel engines on some new brand combine harvesters in the domestic market still use mechanical fuel pumps for fuel supply in low pressure oil circuits. The oil pump is equipped with a manual pumping device to meet the needs of manual pumping and air removal. So why use a hand-operated pump device and often pump it without oil? Mainly because the elastic force of the return spring is greater than the elastic force of the diaphragm spring. When the top rod is at the lowest point of the cam, the diaphragm is in position. At this time, the pressure lever is pulled, and the eccentric finger cannot press on the edge of the rod assembly at all. The bottom edge of the square hole, so it can not complete the diaphragm up and down movement process, that pumping process. Only when the top rod is in the uppermost range of the cam's lifting stroke, ie the top rod is lifted upwards, the return spring is compressed, and the rod assembly is lifted by the diaphragm spring, the pressure rod is rotated, and the eccentric finger passes through the rod. A square hole on the side of the assembly presses the lower rod assembly and the diaphragm to complete the suction process. Loosing the pressure lever, the diaphragm spring can once again push up the diaphragm to complete the fuel pressure process. Therefore, the key to manually pumping the pump oil is to ensure that the top of the hollow top rod is in the cam upstroke; at the highest point, the stroke of the manual pumping oil is the largest and the pump oil effect is also the best. Use your hand to pull the lever and confirm the feel of the hand when pulling the lever. If the pressure bar is pressed, the sense of resistance is strong, and there is a sudden increase in resistance during the 1/2-1/3 stroke after the pressure bar, which means that the cam position is appropriate, as long as the trigger bar is pulled about 300-400 times The pump is full of filter; if there is no sense of resistance, and there is no sudden increase of resistance during the trailing 1/2-1/3 stroke of the pressure rod, it means that the position of the cam is not suitable. Turn the key switch to make the diesel idle. To confirm the feel, the maximum number of idle four or five times can make the cam go to a better pumping position.