A car engine is often compared to a human heart. And there are some similarities. Thanks to the heart, a person can live, and a car thanks to a motor can move. The heart pumps blood in the body - it circulates to all key organs. In the engine, this function is performed by the fuel system. Today we look at the features and purpose of the low pressure pump. This element is a very important part of the food system. TNND is necessary for supply of fuel to TNVD. Often it is installed next to the high pressure fuel pump. Both mechanisms are connected by means of pipes through which circulation is carried out. At the same time, fuel passes through filters, where it is cleaned.
What tasks does TNND solve in the fuel system?
The diesel engine low pressure fuel pump solves an important task.
Low-pressure fuel boils. As a result, steam jams form. Bubbles of vapor of light fractions and denser fuel are separated. This means that a liquid begins to flow into the low-pressure pump, the viscosity of which is constantly changing. There is no need to talk about fuel injection with the help of high-pressure fuel pumps in normal mode. The torch is constantly changing and will not fall into normal parameters.
How is TNND
The diesel engine low pressure fuel pump consists of a drive shaft. Pumping is carried out using a special rotor, on which there are blades. The design also provides a stator, a distribution disk and a drive gear. When the rotor is driven, its blades come closer to the stator. Then, the formation of the chambers is performed due to the action of centrifugal force. Since voltage is created in the pump cavity, the fuel flows directly from them to the high pressure fuel pump. To do this, there are channels in the distribution disk. A small amount of diesel will enter the reduction valve if the pressure is greater than necessary.
Both devices are interconnected, so a special drain choke is used to create and maintain the right conditions. This is a nozzle that is screwed into the high pressure pump. This creates the conditions in the chambers, depending on how fast the drive shaft rotates.
Booster pump device
The low pressure booster or fuel pump (TNND) in diesel power units has a simple design. It consists of two gears that are constantly in engagement with each other. In the process of rotation, the teeth of these gears create a flow of fuel through the fuel system to the high pressure pump. The main structural element in the pump-type pump is a piston that pumps fuel. To supply a diesel engine, two piston operating modes are necessary. This is a working move and an auxiliary one.
Varieties of TNND
A diesel engine low-pressure fuel pump is just one variation of these mechanisms. In addition to diesel, these devices can be found in other engines, regardless of the model of the motor or the year of its production. You can not do without a pump - it is necessary to supply fuel from the fuel tank and transfer it further through the system.
In the case of carburetor gasoline engines, relatively weak mechanical pumps are used. On units equipped with an injection power system, as well as on diesel power units, an electric diesel fuel pump is used.
Mechanical TNND
This system is installed directly on the cylinder block and secured with ordinary screws. The operation of such a pump is ensured by a crankshaft with an eccentric. If you press the eccentric cam, contractions are created inside. So the fuel is fed through the power system. In order for the fuel not to get back, the pump is equipped with a special valve. The remaining pressure on the cam sends gas to the carburetor. If a mechanical type of high-pressure fuel pump is installed in the car, then it is easy to start the engine with it, even taking into account long downtime. To do this, simply manually pump the swap mechanism.
Electric
Modern cars use an electric low-pressure fuel pump for a diesel engine and gasoline injection engine. The use of a mechanical device has become simply impossible. He, due to less power, could not cope with the tasks. It does not create the necessary pressure inside the fuel system.
In a simpler form, the device is a pump element itself and an
electric motor enclosed in one housing. There is also a filter for cleaning fuel, a fuel intake and a fuel consumption sensor. The scheme and principle of operation are similar to the
operation algorithm
of a mechanical unit. The only difference is that an electric motor is used to pump the fluid. In gasoline engines, the high pressure fuel pump is located directly inside the fuel tank. Most car owners are sure that this is not entirely safe. In fact, there is no danger in this. In the case of gasoline, the fuel in the pump is prone to overheating due to the heat generated by the engine. On electrical analogues, this problem is completely absent. Fuel without interruptions moves along the nozzles of the system and prevents the pump from overheating to a critical point. In diesel engines, electric high-pressure fuel pumps are often combined with high-pressure fuel pumps. This can be explained by the need to supply fuel continuously. This ensures stable engine operation at various speeds.
High pressure fuel pump (TNVD)
This device is considered one of the most complex in a diesel engine. Its main task is to ensure the supply of diesel to the combustion chambers under high pressure. The supply is provided not just under a certain pressure, but at the right time. The portion is very accurately measured by electronics and fully corresponds to the level of load on the unit. There are several types of devices according to the type of injection. These are units with a battery injection system and with direct action.
The device of a
high-pressure fuel pump of a diesel engine, in which the direct principle of action is applied, is characterized in that a plunger equipped with a mechanical drive type is used in the design. So, injection and injection are performed simultaneously. A separate section of the pump sprays a dose of fuel into each combustion chamber. The necessary pressure is provided due to the movement of the plunger mechanism.
Cordless fuel injection pump and their features
Pumps equipped with battery injection have differences. So, the pressurized gases in the engine cylinders will act on the working drive of the plunger. Also, the impact can be exerted using springs. Nowadays, devices with a hydraulic type battery are common. They are installed in powerful motors, working mainly at low speeds.
The main malfunctions TNND
The main problem is a decrease in the device’s performance and a drop in the injection level, which was provided by the diesel engine’s low-pressure fuel pump. It can be determined using a manometer or a pressure sensor, which is installed at the inlet.
Most often, the reasons for the decrease in the performance of the high pressure fuel pump are blockage and jamming of the working element. As for the first reason, various impurities can be contained in diesel fuel, which, although passing through the filter elements, nevertheless accumulate in the valve. It is also possible that the elasticity of the return spring of the element has decreased.
How to repair fuel pump
If the efficiency of the unit has fallen, the diesel engine low pressure fuel pump must be dismantled and audited. Often, productivity rises again after washing and cleaning the working cavities and elements of the device.
It will also be useful to drain garbage and tar from the drainage compartments. For more serious repairs, use repair kits, which are now available at Chinese factories that manufacture spare parts for car engines.
Knowing how the low-pressure fuel pump of a diesel engine is arranged , the principle of operation of the device, you can easily repair it or replace it.