You may have heard this name for a fuel pump part, but what a plunger is, where it is located and how it works remains unclear.
A plunger is a specific piston shape, cylindrical in shape. Its length exceeds its diameter many times. A distinctive feature of this part is that its seal is located in the cylinder and does not move during the return movement. It is used in pump mechanisms where it is necessary to obtain high fuel supply pressure, compared to simple valve pumps.
The concept of “plunger pair”
The plunger and its bushing are very precisely fitted to each other, which is why the mechanism is called a plunger pair. In case of failure, replacement is carried out only in pairs. Similar parts are used today in hydraulic compensators, hydraulic units, pumps, and other units that create fluid pressure. The popularity of these parts is due to their reliability, simplicity of design and efficiency.
Injection pump plunger pair
We will discuss the functions of the plunger pair in more detail using the example of a diesel engine injection pump. As the name suggests, the pump pumps diesel fuel from the main tank into a high-pressure line (for example, a fuel rail), from where it is sprayed into the engine cylinders under strong pressure.
The main element that creates such pressure is the plunger pair. Next, the fuel is distributed among the cylinders in accordance with the design of the fuel system. The types of pumps are described in another article .
During pump operation, pushers and drive return springs move the piston up/down inside the plunger sleeve, causing it to perform reciprocating movements. So the design sucks diesel fuel through hoses from the fuel tank and pumps it into a closed tank, thereby creating pressure in it. To prevent this parameter from increasing excessively, the pump device has a number of valves designed to retain or relieve excess pressure in the system.
