The fuel pump is designed to supply fuel from the tank to the car engine. It provides a uniform dosage and a constant pressure necessary for the correct operation of the motor. In the automotive industry, several types of pumps are used, which differ not only in design, but also in the type of drive. How the most popular fuel pumps are arranged will be discussed further.
Content
Fuel pump device
Mechanical fuel pumps
Electrically driven fuel pumps
Features of the fuel pumps
Main malfunctions and resource of fuel pumps
Fuel pump device
Depending on the type of drive, fuel pumps are divided into two large groups: mechanical and electrical. The former are used only in carburetor engines, as well as booster pumps in diesel engines. The second applies to both gasoline and diesel engines.
Mechanical fuel pumps
Mechanical fuel pump device
The mechanical pump is located on the engine and is driven by a special eccentric. Structurally, it consists of the following elements:
frame;
diaphragm;
толкатель;
stock;
return spring;
valves on the suction and discharge channels;
filter;
eccentric.
In cars equipped with rear-wheel drive, the eccentric is located on the oil pump drive shaft , and in cars with front-wheel drive, it is located on the engine camshaft. The movement of the diaphragm in such a pump ensures the movement of fuel. When the diaphragm is at its lowest point, a vacuum occurs in the working chamber, and the latter is filled with liquid. When the diaphragm moves to the top position, the fuel is pushed into the discharge pipe. Valves at the same time prevent the reverse flow of fuel.
For diesel engines, such systems are often used as low pressure pumps. They perform the function of pumping fuel and are located next to the high pressure pumps ( TNVD ). On the practical side, this makes it possible to overcome the hydraulic resistance of the filtration system and create a stable overpressure.
Electrically driven fuel pumps
Roller fuel pump. 1 - check valve; 2 - safety valve; 3 - electrical connector; 4 - electric motor; 5 - impeller
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Electric pumps are installed on engines with distributed and direct injection. They are powered by an electric drive from a battery or generator . According to their device, electric pumps are divided into the following groups:
Vacuum. Such a pump has a similar design with a mechanical one, but the eccentric that drives the working units has been replaced with an electric drive.
Roller. In such a device, the fuel moves due to the rotation of the rotor (movement of the rollers). At the moment when the distance between the roller and the rotor increases, a vacuum occurs, the suction valve opens, and the fuel is sucked in until it is completely filled. At the next moment, the rotation of the rotor ensures a decrease in the distance, and through the opened delivery valve, fuel is supplied to the engine.
Gear. Suction and injection of fuel is realized due to the rotation of the gear-rotor. It is located eccentrically with respect to the stator gear. The teeth of the gears form chambers through which the fuel flows. During rotation, the volumes of the chambers are constantly changing, which provides the desired pressure.
Centrifugal. Such a pump has an impeller equipped with blades that move the fuel from the suction to the discharge channel. The pressure is created due to the turbulence that occurs when the blades act on the working fluid.
Plunger. Gasoline pumps of this design are rare. Such systems are mainly used in diesel-fueled vehicles as injection pumps. They have pairs of plungers driven by a camshaft. When the plunger moves upwards, the outlet and inlet holes are successively closed. This forms the pressure necessary to open the discharge valve and the subsequent supply of fuel to the engine injectors .
Features of the fuel pumps
Submersible fuel pump
To determine where the electric fuel pump is located in the system, it is necessary to take into account its design features. For example, rotary and gear pumps are installed directly in the fuel line system, and the centrifugal pump is always located in the gas tank . By location, fuel pumps are divided into:
Remote - mounted on the car body.
Submersible - installed in the fuel tank so that it is immersed in fuel. Such designs are most popular in modern cars. By immersing the mechanism in the working fluid, it is cooled, and the possibility of a “dry run” is also excluded. The submersible fuel pump module consists of a fuel level sensor, a coarse fuel filter , the electric fuel pump itself and a pressure regulator.
In cars with a gasoline engine, the fuel pump creates a high pressure in the range of 0.3-0.4 MPa. In direct fuel injection systems, pressures up to 0.7 MPa can be provided.
The electric pump is switched on using a relay that receives a signal from the engine control unit. Power passes through the fuse in the fuel pump circuit, bringing the latter into operation simultaneously with the ignition system being turned on or immediately after opening the driver's door. The relay itself can be located near the engine control unit or as part of the fuse box.
Main malfunctions and resource of fuel pumps
The life of any fuel pump is affected by the quality of the fuel. On average, the service life is up to 200 thousand kilometers, but the first malfunctions can occur after 100 thousand kilometers.
Gasoline pump grid
The most common problem is system contamination. It leads to damage and jamming of the working parts of the mechanism. In order to prevent such malfunctions, a fuel pump cleaning filter (mesh) is installed. For submersible structures, in addition to quality, the amount of remaining fuel in the tank is also fundamental. If it is not enough, the motor overheats and does not receive sufficient cooling.
Quite often, a fuel level sensor is located on submersible pumps. It works on the following principle: the fuel pump sensor float always floats on the surface of the liquid in the tank. Depending on its position, the sensor sends signals and notifies the driver about the need to refill the tank.
Experts recommend not to allow the fuel level in the tank to drop below 5-10 liters.
One of the most common causes of failure to start the engine is a blown fuel pump fuse. In this case, it will require replacement. The location of the fuse itself depends on the brand of car. It can be both the engine compartment and the interior of the car.
It is quite difficult to diagnose a fuel pump malfunction when inspecting a car. However, clear signs are the presence of errors in the fuel level sensor or fuel rail pressure sensor. Errors can be read by an automotive scanner, for example, by the Rokodil ScanX Pro universal multi-brand device.
