What is a plunger pair? Production, repair, replacement and adjustment of plunger pairs

The high-pressure fuel pump (HP injection pump) is one of the most important components of any diesel engine. It is with the help of this part that the fuel is delivered in such a way that the fuel-air mixture does not enter the chamber, but the liquid. The work of the injection pump is significantly affected by the plunger pair. Due to this element, distribution and supply of fuel to the motor are carried out. And today we will consider what a plunger pair is, what value it has for a diesel car.

Device

The design of this element assumes the presence of two basic elements - the bushing and the plunger. The latter consists of a small piston of cylindrical shape. When the pump is running, this part moves inside the hub. Due to the reciprocating movements that they produce, the fuel is injected, after which the fuel is sucked. The plunger pair of the injection pump (the photo of this element you can see below) has holes on the sleeve. Through them, diesel fuel is supplied for injection.

That is, the main purpose and function of this element is to measure the exact amount of fuel for its supply to the cylinders of the engine. In addition, with the help of this element, the pump supplies fuel at a certain pressure at the right time. But in order to carry out all these operations without failure, the plunger pair must meet a number of technical requirements. The very same production is carried out on high-tech equipment (usually in large enterprises). At home, such an element can not be made.

About injection valves as an integral part of the fuel system

The main task of this element is to close the high-pressure lines between the plunger and the fuel line. This results in a reduction in the fuel pressure, which is necessary to more accurately and quickly close the nozzles of the injector. This prevents the formation of droplets of fuel, and their presence there is extremely undesirable. During injection, the pressure that is created in the space above the plunger lifts the cone of the discharge valve. Further the fuel under pressure gets to the atomizer through the fuel line and the valve holder. Once the plunger groove opens the drain channel, the pressure level in the chamber drops, and the spring of the discharge valve presses the device body back to the seat. This action takes place in the system until the plunger starts a new working stroke.

Is plunger leaking possible?

In qualitative details, the probability of fuel leakage is zero. To minimize the likelihood of fuel leakage, the gap between the bushing and the plunger is made to be 1-3 μm. Because of this high precision, each plunger is selected separately to the bushing. After that, the factory adjusts both parts. During the manufacturing process, the surface of these elements is additionally hardened. This is done to ensure the longest possible life of this part.

Operating the part

The plunger pair is an element that requires special attention during the operation of the car and the operation of its fuel system. The guarantee of high-quality and uninterrupted operation of this part is the use of only high-quality fuel. Unfortunately, few domestic gas stations monitor the quality of fuel, so our car owners (especially those with diesel cars) often have to repair and clean the injectors.

The content of various chemical impurities and the high concentration of dirt and deposits significantly reduce the service life of the plunger pairs.
Water has a particularly negative effect, which is also sometimes contained in domestic fuels. When it enters the gap between the bushing and the plunger, the integrity of the lubricating film is impaired, resulting in the device starting to work without lubrication. This can lead to increased heating, deformation and even jamming of a part such as a plunger pair. In this case, the only way out of the situation is to replace the device with a new one. In order to avoid such troubles, it is necessary to regularly diagnose fuel equipment and, if possible, not refuel at unfamiliar gas stations.

When is it necessary to replace the plunger pair?

There are several basic symptoms that indicate a malfunction of this part. One of them is the failure to start the engine. But to determine the breakdown of the plunger pair is possible even with the engine running. In this case, it is necessary to pay attention to the quality of the motor. If it works unstably and with interruptions, most likely, the reason is hidden in the fuel system. Also, with a malfunctioning plunger pair, the motor starts to lose its power considerably and produce extraneous sounds that did not occur before. If you notice at least one of the above symptoms, you need to diagnose the fuel system of the car.

It is worth noting that for this you need to have special diagnostic equipment. Therefore, with your own hands and without the appropriate equipment, you can hardly determine the serviceability of the plunger. After diagnostics, the master decides whether adjustment of the plunger pair is necessary or completely replaced with a new one. During the repair, certain equipment is used, which restores the factory hermetic dimensions of the plunger and bushing. The very replacement also requires special care, knowledge and experience, so it's extremely dangerous to do something in the injection pump with your own hands, since this can disable the whole system in the car.

Conclusion

So, we found out how the plunger pairs affect the injection pump and all their design features. In general, the fuel system of a diesel engine is a very complex mechanism, requiring special attention and extremely high-quality fuel. In this regard, the number of diesel cars in our country is an order of magnitude lower than in Western Europe. After all, it's almost impossible to service the fuel with your own hands, and spending money on expensive repairs and diagnostics is unlikely to anyone to want.