It is well known that the piston is the "heart" of the automobile engine, bears alternating mechanical load and thermal load, and is one of the key components in the engine with extremely harsh working conditions. The function of the piston is to withstand gas pressure and transmit it to the connecting rod through the piston pin to drive the crankshaft to rotate. The top of the piston is also a component of the combustion chamber. I found on the Internet that the working principle of the piston pump is that during the reciprocating movement of the piston, when the piston moves outward, the outlet check door is closed under the action of its own weight and pressure difference, and the inlet check door is opened under the action of the pressure difference. Suck the liquid into the pump chamber. When the piston presses inward, the pressure in the pump chamber rises, causing the inlet check door to close, and the outlet check door to open to press the liquid into the outlet pipe. I hope the information I found is helpful to you.