Like the human heart, the fuel pump circulates fuel in the fuel system. For gasoline engines, this role is played by an electric gas pump, and for diesel engines - by a fuel pump. high pressure(Injection pump).
This unit performs two functions: it pumps fuel into the nozzles in a strictly defined amount and determines the moment when it starts to be injected into the cylinders. The second task is similar to changing the ignition timing for gasoline engines. However, since the advent of battery injection systems, the timing of the injection is controlled by the electronics that control the injectors.
The main element of the high pressure fuel pump is the plunger pair. Its structure and principle of operation will not be considered in detail in this article. In short, the plunger pair is a long piston of small diameter (its length is several times the diameter), and the working cylinder, fitted very accurately and tightly to each other, the gap is a maximum of 1-3 microns (for this reason, in the case of failure, the whole pair changes). One or two intake channels are located in the cylinder, through them fuel enters inside, which is then pushed out by the piston (plunger) through the exhaust valve.
The principle of operation of the plunger pair is similar to the operation of a two-stroke engine. internal combustion... Moving down, the plunger creates a vacuum inside the cylinder and opens the intake port. Fuel, obeying the laws of physics, strives to fill the rarefied space inside the cylinder. After that, the piston starts to rise. At first, it closes the inlet channel, then raises the pressure inside the cylinder, as a result of which the exhaust valve opens, and the fuel is supplied under pressure to the nozzle.
There are three types of injection pumps, they have a different device, but one purpose:
In the first of them, a separate plunger pair is injected into each cylinder, respectively, the number of pairs is equal to the number of cylinders. The high-pressure fuel distribution pump circuit is significantly different from the in-line circuit. The difference lies in the fact that the fuel is pumped to all cylinders by means of one or more plunger pairs. The main pump pumps fuel into the accumulator, from which it is subsequently distributed to the cylinders.
In a car with gasoline engines, with a direct injection system, the fuel is pumped by an electric high-pressure fuel pump, but it (pressure) there is several times less.
As already mentioned, it has plunger pairs according to the number of cylinders. Its structure is quite simple. The vapors are housed in a housing, inside of which there are underwater and branch fuel channels. In the lower part of the body there is a camshaft driven by the crankshaft, the plungers are constantly pressed against the cams by springs. 
The principle of operation of such a fuel pump is not very complicated. The cam, when rotating, runs onto the plunger pusher, forcing it and the plunger to move upward, compressing the fuel in the cylinder. After closing the outlet and inlet channels (in this sequence), the pressure begins to rise to a value after which the discharge valve opens, after which diesel fuel is supplied to the corresponding nozzle. This scheme resembles the operation of the engine gas distribution mechanism.
To regulate the amount of incoming fuel, and the moment of its supply, either a mechanical method or an electrical one is used (such a scheme assumes the presence of control electronics). In the first case, the amount of supplied fuel is changed by turning the plunger. The circuit is very simple: it has a gear, it meshes with the rack, which, in turn, is connected to the accelerator pedal. The upper surface of the plunger is tilted, which changes the timing of closing the inlet in the cylinder, and hence the amount of fuel.
The moment of fuel supply must be changed when changing the value of the crankshaft revolutions. To do this, the camshaft has a centrifugal clutch, inside which weights are located. With increasing speed, they diverge, and the camshaft rotates relative to the drive. As a result, when the speed rises, the fuel pump provides an earlier injection, and with a decrease - a later one. 
The device of in-line injection pumps provides them with a very high reliability and unpretentiousness. Since lubrication occurs with engine oil from the lubrication system power unit, this makes them suitable for low quality diesel fuel.
In-line injection pumps are installed on medium and heavy trucks. They were completely removed from passenger cars in 2000.
Unlike an in-line fuel pump, a distribution pump has only one or two plunger pairs that supply fuel to all cylinders. The main advantages of such fuel pumps are lighter weight and size, as well as more uniform fuel supply. The main disadvantage is one - their service life is much shorter due to the high load, therefore they are used only on passenger cars.
There are three types of distribution injection pumps:
The device of the first two types of pumps provides them with a longer service life, in comparison with the latter, because there are no power loads on the drive shaft units from the fuel pressure in them.
The scheme of operation of the distribution fuel pump of the first type is as follows. The main element is the plunger-distributor, which, in addition to the translational-return movement, rotates around its axis, and thereby pumps and distributes the fuel between the cylinders. It is driven by a cam washer running around the stationary ring on the rollers. 
The amount of supplied fuel is controlled both mechanically, using the above-described centrifugal clutch, and by means of a solenoid valve, to which an electrical signal is applied. The advance of fuel injection is determined by turning the fixed ring at a certain angle.
The rotary scheme assumes a slightly different arrangement of the fuel distribution pump. The operating conditions of such a pump are somewhat different from how an injection pump with an end cam drive works. The fuel is pumped and distributed, respectively, by two opposing rams and a distributor head. By rotating the head, the fuel is redirected to the corresponding cylinders.
The in-line fuel pump drives fuel into the fuel rail and provides a higher pressure than in-line and distribution pumps. The scheme of its work is somewhat different. Fuel can be pumped with one, two or three plungers driven by a cam washer or shaft. 
The fuel supply is regulated by an electronic metering valve. The normal state of the valve is open, when an electrical signal is received, it partially closes and thereby regulates the amount of fuel entering the cylinders.
Fuel pump low pressure, is necessary to supply fuel to the high pressure fuel pump. As a rule, it is installed either on the high-pressure pump housing or separately, and pumps fuel from the gas tank, through coarse filters, and then fine filters, directly into the high-pressure pump.
The principle of its operation is as follows. It is driven by an eccentric located on the camshaft of the injection pump. The pusher, pressed against the rod, makes the rod with the piston move. The pump housing has inlet and outlet channels that are closed off by valves. 
The scheme of operation of the TNND is as follows. The working cycle of the low pressure fuel pump consists of two strokes. During the first, preparatory, the piston moves down and fuel is sucked into the cylinder from the tank, while the discharge valve is closed. When the piston moves up, the inlet channel is closed off by the suction valve, and under increasing pressure, the outlet valve opens, through which the fuel enters the fine filter and then into the high-pressure fuel pump.
Since the low pressure fuel pump has a capacity greater than that required for the engine to operate, part of the fuel is pushed into the cavity under the piston. As a result, the piston loses contact with the pusher and freezes. As fuel runs out, the piston descends again and the pump resumes operation.
Instead of a mechanical one, an electric low-pressure fuel pump can be installed on the car. Quite often it is found on cars that are equipped with Bosch pumps (Opel, Audi, Peugeot, etc.). The electric pump is installed only on cars and small minibuses. In addition to its main function, it serves to cut off the fuel supply in the event of an accident.
The electric low-pressure fuel pump begins to operate simultaneously with the starter and continues to pump fuel at a constant speed until the engine is turned off. Excess fuel is drained back into the tank through the bypass valve. An electric pump is placed either inside the fuel tank or outside it, between the tank and the fine filter.
In the previous series of articles on the device of the fuel system of a gasoline engine, the topic of a high-pressure fuel pump for a diesel engine and gasoline engines with direct (direct) fuel injection was repeatedly touched upon.
This article is a separate material that describes the design of a high pressure diesel fuel pump, its purpose, potential malfunctions, diagram and principles of operation using the example of such a fuel supply system for this type. So let's get straight to the point.
Read in this article
The high pressure fuel pump is abbreviated as. This device is one of the most complex in the design of a diesel engine. The main task of such a pump is to supply diesel fuel under high pressure.
Pumps provide fuel supply to the cylinders of a diesel engine under a certain pressure, as well as strictly at a certain moment. The portions of the supplied fuel are measured very accurately and correspond to the degree of load on the engine. High pressure fuel pumps are distinguished by the injection method. There are direct-acting pumps as well as battery injection pumps.
Direct-acting fuel pumps have a mechanical plunger drive. The fuel injection and fuel injection processes take place at the same time. In each individual cylinder of a diesel internal combustion engine, a specific section of the injection pump supplies the required dose of fuel. The pressure required for effective atomization is generated by the movement of the fuel pump plunger.
The high-pressure fuel pump with accumulator injection is distinguished by the fact that the pressure forces of compressed gases in the cylinder of the internal combustion engine itself act on the drive of the working plunger, or the action is exerted by means of springs. There are fuel pumps with a hydraulic accumulator, which have found application in powerful low-speed diesel internal combustion engines.
It should be noted that systems with a hydraulic accumulator are characterized by separate pumping and injection processes. Fuel under high pressure is pumped into the accumulator by the fuel pump, and only then goes to the fuel injectors. This approach ensures efficient atomization and optimal mixture formation, which is suitable for the entire load range of the diesel engine. The disadvantages of this system include the complexity of the design, which was the reason for the unpopularity of such a pump.
Modern diesel installations use a technology that is based on the control of the solenoid valves of the injectors from an electronic control unit with a microprocessor. This technology was named "Common Rail".
The injection pump is an expensive device that is very demanding on the quality of fuel and lubricants. If the car is operated on low quality fuel, such fuel must contain solid particles, dust, water molecules, etc. All this leads to the failure of the plunger pairs, which are installed in the pump with a minimum tolerance measured in microns.
Low-quality fuel easily destroys the injectors, which are responsible for the process of atomization and injection of fuel.
Common signs of malfunctions in the operation of injection pumps and injectors are the following deviations from the norm:
Modern engines with high pressure fuel pumps are equipped with an electronic fuel injection system. doses the fuel supply to the cylinders, distributes this process over time, determines the required amount of diesel fuel. If the owner notices the slightest interruptions in the operation of the engine, then this is an urgent reason to immediately contact the service. The power plant and fuel system are thoroughly examined using professional diagnostic equipment. During the diagnosis, specialists determine numerous indicators, among which the primary ones are:
Increasingly stringent environmental and emission regulations have led to the displacement of mechanical high-pressure fuel pumps for diesel vehicles by electronically controlled systems. The mechanical pump simply could not provide fuel metering with the required high accuracy, and was also not able to respond as quickly as possible to dynamically changing engine operating modes.
The key element in this system is the device for moving the injection pump metering sleeve (10). The control unit (6) controls the fuel supply processes. Information comes to the unit from sensors:
The preset optimum characteristics are stored in the memory of the control unit. Based on the information from the sensors, the ECU sends signals to the control mechanisms for the cyclic feed and the injection advance angle. This is how the value of the cyclic fuel supply is adjusted in various operating modes of the power unit, as well as at the time of cold start of the engine.
The actuators have a potentiometer that sends a feedback signal to the ECU, thereby determining the exact position of the metering clutch. The fuel injection advance angle is adjusted in a similar manner.
The ECU is responsible for generating signals that regulate numerous processes. The control unit stabilizes the speed in the mode idle move, regulates the recirculation of exhaust gases with the determination of indicators according to the signals of the mass air flow sensor. The block compares signals in real time from sensors with those values that are programmed in it as optimal ones. Further, the output signal from the ECU is transmitted to the servo mechanism, which provides the required position of the metering clutch. This achieves a high control accuracy.
This system has a self-diagnosis program. This makes it possible to carry out emergency modes to ensure the movement of the vehicle even in the presence of a number of certain malfunctions. A complete failure occurs only when the ECU microprocessor breaks down.
The most common solution for cyclic flow control for a distribution type high pressure single plunger pump is to use an electromagnet (6). Such a magnet has a rotatable core, the end of which is connected by means of an eccentric to a metering sleeve (5). Electric current flows in the winding of the electromagnet, while the rotation angle of the core can be from 0 to 60 °. This is how the metering sleeve (5) moves. As a result, this clutch regulates the cyclic feed of the injection pump.
The automatic injection advance is controlled by a solenoid valve (2). This valve regulates the fuel pressure, which acts on the piston of the machine. The valve is characterized by operation in a pulse mode according to the "open-close" principle. This makes it possible to modulate the pressure, which depends on the engine speed. At the moment the valve opens, the pressure drops, and this entails a decrease in the injection advance angle. A closed valve provides an increase in pressure, which moves the piston of the machine to the side when the injection advance angle is increased.
These EMC pulses are determined by the ECU and depend on the operating mode and temperature indicators of the engine. The injection start point is determined by the fact that one of the injectors is equipped with an inductive needle lift sensor.
The actuators that affect the fuel supply control elements in the distribution type injection pump are proportional electromagnetic, linear, torque or stepper motors that act as a drive for the fuel metering device in these pumps.
The electromagnetic actuator of the distribution type consists of a dispenser stroke sensor, the actuator itself, a dispenser, an injection angle change valve, which is equipped with an electromagnetic drive. 
The injector has a built-in excitation coil (2) in its housing. The ECU supplies a certain reference voltage there. This is done to keep the current in the electrical circuit constant and independent of temperature fluctuations.
The nozzle equipped with a needle lift sensor consists of:
This current results in the creation of a magnetic field around the coil. At the moment of raising the nozzle needle, the core (3) changes the magnetic field. This causes a change in voltage and signal. When the needle is in the process of lifting, then the pulse reaches its peak and is detected by the ECU, which controls the injection advance angle.
The electronic control unit compares the received impulse with the data in its memory, which correspond to different modes and operating conditions of the diesel unit. The ECU then sends a return signal to the solenoid valve. The specified valve is connected to the working chamber of the injection timing machine. The pressure acting on the piston of the machine begins to change. The result is the movement of the piston under the action of the spring. This is how the injection advance angle changes.
The maximum pressure indicator that is achieved using electronic control the fuel supply based on the VE fuel pump is 150 kgf / cm2. It should be noted that this scheme is complex and outdated, the voltages in the cam drive have no further development prospects. The next stage in the development of high-pressure fuel pumps is a new generation of circuits.
This scheme is successfully applied on the latest models of diesel cars from the world's leading concerns. These include BMW, Opel, Audi, Ford, etc. Pumps of this type make it possible to obtain an injection pressure at around 1000 kgf / cm2.
The direct injection system with a VP-44 fuel pump, shown in the figure, includes:
This system has a characteristic feature, which consists in a combined control unit for the injection pump and other systems. The control unit structurally has two parts, the final stages and the power supply of the electromagnets located on the fuel pump housing.
The system works in such a way that the torque from the drive shaft is transmitted through the connecting washer and the splined connection. This moment goes to the distributor shaft. The guide grooves (3) perform such a function that, through the shoes (4) and the rollers (2) located in them, the pumping plungers (5) are put into operation so that this corresponds to the inner profile that the cam washer (1) has. The number of cylinders in a diesel engine is equal to the number of cams on the washer.
The delivery plungers in the distributor shaft housing are arranged radially. For this reason, such a system was called injection pump. Plungers carry out joint extrusion of the supplied fuel on the upward profile of the cam. Further, the fuel enters the main high pressure chamber (7). The injection pump can have two, three or more pumping plungers, which depends on the planned loads on the motor and the number of cylinders (a, b, c).
This device is based on:
In the figure below, we see the distribution housing itself:
This system consists of:
During the filling phase, on the descending profile of the cams, the plungers (1), which move radially, move outward and move towards the surface of the cam washer. The locking needle (4) at this moment is in a free state and opens the inlet fuel channel. The fuel flows through the low pressure chamber (12), the annular channel (9) and the needle. Further, the fuel is directed from the fuel pump through the channel (8) of the distributor shaft and enters the high pressure chamber. All excess fuel flows back through the return drain channel (5).
The injection is carried out using plungers (1) and a needle (4), which is closed. The plungers begin to move on the upward profile of the cams towards the distributor shaft axis. This is how the pressure in the high-pressure chamber increases.
The fuel, already under high pressure, rushes through the channel of the high-pressure chamber (8). It passes the distribution groove (13), which in this phase connects the distribution shaft (2) with the outlet (14), the union (16) with the discharge valve (15) and the high-pressure line with the nozzle. The last stage is the flow of diesel fuel into the combustion chamber of the power plant.
The solenoid valve (valve for setting the moment of the start of injection) consists of the following elements:
The specified solenoid valve is responsible for the cyclic supply and metering of fuel. The specified high pressure valve is built into the high pressure circuit of the high pressure fuel pump. At the very beginning of the injection, voltage is applied to the solenoid coil (5) according to the signal from the control unit. The anchor (4) moves the needle (3) by pressing the latter against the saddle (1).
When the needle is pressed firmly against the seat, then no fuel will flow. For this reason, the fuel pressure in the circuit rises rapidly. This allows the corresponding nozzle to be opened. When the required amount of fuel is in the combustion chamber of the engine, then the voltage on the coil of the electromagnet (5) disappears. The high pressure solenoid valve opens, causing a pressure drop in the circuit. A drop in pressure causes the fuel injector to close and stop injection.
All the accuracy with which this process is carried out directly depends on the solenoid valve. If you try to explain in even more detail, then from the moment the valve ends. This moment is solely determined by the absence or presence of voltage on the solenoid valve coil.
Excess fuel injected, which continues to be injected until the plunger roller passes the upper point of the cam profile, move along a special channel. The end of the fuel path is the space behind the storage membrane. In the low pressure circuit, there are high pressure surges, which are damped by an accumulation diaphragm. In addition, this space stores (stores) the accumulated fuel for filling before the next injection.
The engine is stopped using a solenoid valve. The fact is that the valve completely blocks the injection of fuel under high pressure. This solution completely eliminates the need for an additional stop valve, which is used in distribution injection pumps, where the control edge is controlled.
This delivery valve (15) with a throttling of the reverse flow after the completion of the injection of a portion of fuel prevents the next opening of the injector nozzle. This completely eliminates such a phenomenon as additional injection, which is the result of pressure waves or their derivatives. This additional post-injection increases the toxicity of the exhaust gases and is an extremely undesirable negative phenomenon.
When the fuel supply starts, then the valve cone (3) opens the valve. At this very moment, the fuel is already pumped through the nozzle, enters the high-pressure line and is directed to the injector. The end of fuel injection causes a sharp drop in pressure. For this reason, the return spring forces the valve plug back against the valve seat. Backward pressure waves are generated when the nozzle is closed. These waves are successfully damped by the throttle of the discharge valve. All these actions prevent unwanted injection of fuel into the working chamber of the diesel engine combustion.
This device consists of the following elements:
The optimal combustion process and the best power characteristics with respect to the diesel internal combustion engine are possible only when the moment of the beginning of the combustion of the mixture occurs in a certain position of the crankshaft or piston in the cylinder of the diesel engine.
The injection advance device performs one very important task, which is to increase the angle of the start of fuel delivery at the moment when there is an increase in the crankshaft speed. This device structurally includes:
The device provides the very optimal moment of the start of injection, which is ideally suited to the operating mode of the engine and the load on it. Compensation occurs for a time shift, which is determined by the shortening of the injection and ignition period with increasing speed.
This device is equipped with a hydraulic drive and is built into the lower part of the injection pump housing so that it is located across the longitudinal axis of the pump.
The cam washer (1) makes the entry of the ball pin (2) into the transverse bore of the plunger (3) in such a way that the translational movement of the plunger is transformed into a rotation of the cam washer. The plunger has a control valve (5) in the center. This valve opens and closes the pilot hole in the plunger. On the axis of the plunger (3) there is a control piston (12), which is loaded with a spring (10). The piston is responsible for the position of the control valve.
The solenoid valve for setting the moment of the start of injection (15) is located across the axis of the plunger. The electronic unit that controls the high-pressure fuel pump acts on the plunger of the injection advance device through this valve. The control unit supplies current pulses in a continuous mode. These pulses are characterized by a constant frequency and variable duty cycle. The valve changes the pressure that acts on the control piston in the structure of the device.
This material is aimed at the most accessible and understandable acquaintance of users of our resource with the complex structure of a high-pressure fuel pump and an overview of its main elements. Device and general principle the operation of the high-pressure fuel pump makes it possible to speak of trouble-free operation only if the diesel unit is filled with high-quality fuel and engine oil.
As you already understood, low-grade diesel fuel is the main enemy of complex and expensive diesel fuel equipment, the repair of which is often not very cheap.
If you operate the diesel engine with care, strictly observe and even shorten the service intervals for replacement lubricant, take into account other important requirements and recommendations, then the injection pump will certainly answer its caring owner with exceptional reliability, efficiency and enviable durability.
Used on a wide variety of vehicles and equipment, it is based on the combustion of a fuel-air mixture and the energy released as a result of this process. But in order for the power plant to function, fuel must be supplied in portions at strictly defined times. And this task lies with the power supply system, which is part of the motor design.
Fuel supply systems for engines are made up of a number of building blocks, each with its own purpose. Some of them filter the fuel, removing polluting elements from it, while others carry out dosage and supply it to the intake manifold or directly to the cylinder. All these elements perform their function with fuel, which still needs to be supplied to them. And this is provided by the fuel pumps used in the design of systems.
Pump assembly
As with any liquid pump, the task of the unit used in the design of the motor is to pump fuel into the system. Moreover, almost everywhere it is necessary that it be supplied under a certain pressure.
Different types of engines use their own types of fuel pumps. But in general, they can all be divided into two categories - low and high pressure. The use of a particular unit depends on the design features and the principle of operation of the power plant.
So, in gasoline engines, since the flammability of gasoline is much higher than diesel fuel, and at the same time the fuel-air mixture from a third-party source ignites, high pressure in the system is not required. Therefore, the design uses low pressure pumps.
Gasoline engine pump
But it is worth noting that in the latest generation gasoline injection systems, fuel is fed directly into the cylinder (), so gasoline must be supplied already under high pressure.
As for diesel engines, their mixture ignites from the influence of pressure in the cylinder and temperature. In addition, the fuel itself is directly injected into the combustion chambers, therefore, in order for the injector to be able to inject it, significant pressure is needed. And for this, a high pressure pump (high pressure pump) is used in the design. But we note that it was not without the use of a low-pressure pump in the design of the power system, since the injection pump itself cannot pump fuel, because its task includes only compression and supply to the injectors.
All pumps used on power plants different types can also be divided into mechanical and electrical. In the first case, the unit is powered by a power plant (a gear drive or shaft cams are used). As for the electric ones, they are driven by their own electric motor.
More specifically, only low-pressure pumps are used on gasoline engines. And only in the injector with direct injection there is a high-pressure fuel pump. At the same time, in carburetor models, this unit had a mechanical drive, but in injection models, electrical elements are used.
Mechanical fuel pump
In diesel engines, two types of pumps are used - low pressure, which pumps fuel, and high pressure, which compresses diesel fuel before it enters the nozzles.
The diesel fuel priming pump is usually mechanically driven, although there are electric models. As for the injection pump, it is brought into operation from the power plant.
The difference in pressure generated between low and high pressure pumps is very striking. So, for the operation of the injection power system, only 2.0-2.5 bar is enough. But this is the working pressure range of the injector itself. The fuel pumping unit, as usual, provides it with a little excess. Thus, the pressure of the injector fuel pump varies from 3.0 to 7.0 bar (depending on the type and condition of the element). As for the carburetor systems, gasoline is supplied there with practically no pressure.
But in diesel engines, a very high pressure is needed to supply fuel. If we take the latest generation Common Rail system, then the diesel fuel pressure in the "injection pump" circuit can reach 2200 bar. Therefore, the pump is powered by a power plant, since it requires a lot of energy to function, and it is not advisable to install a powerful electric motor.
Naturally, the operating parameters and the generated pressure affect the design of these assemblies.
We will not disassemble the gasoline pump device of the carburetor engine, since such a power system is no longer used, and it is structurally very simple, and there is nothing special about it. But the electric fuel injector pump should be considered in more detail.
It is worth noting that different machines use different types fuel pumps differing in design. But in any case, the unit is divided into two components - mechanical, which provides fuel injection, and electrical, which drives the first part.
Pumps can be used on injection vehicles:
Rotary pumps
And the difference between them mainly comes down to the mechanical part. And only the device of the vacuum type fuel pump is completely different.
The operation of the vacuum pump is based on a conventional gasoline pump of a carburetor engine. The only difference is in the drive, but the mechanical part itself is almost identical.
There is a membrane that divides the working module into two chambers. In one of these chambers, there are two valves - the inlet (connected by a channel to the tank) and the outlet (leading to the fuel line, which supplies fuel further to the system).
This membrane, when moving in translation, creates a vacuum in the chamber with valves, which leads to the opening of the inlet element and the injection of gasoline into it. In reverse movement, the intake valve closes, but the exhaust valve opens and the fuel is simply pushed into the line. In general, everything is simple.
With regard to the electrical part, it works on the principle of a pull-in relay. That is, there is a core and a winding. When voltage is applied to the winding, the magnetic field arising in it draws in the core connected to the membrane (its translational movement occurs). As soon as the voltage disappears, the return spring returns the diaphragm to its original position (return movement). The supply of pulses to the electrical part is controlled by the electronic injector control unit.
As for the other types, their electrical part is, in principle, identical and is a conventional electric motor. direct current, powered by a 12 V network. But the mechanical parts are different.
Roller fuel pump
In a roller type pump, the working elements are a rotor with grooves made in which rollers are installed. This design is placed in a housing with an internal cavity of a complex shape, which has chambers (inlet and outlet, made in the form of grooves and connected to the supply and outlet lines). The essence of the work boils down to the fact that the rollers simply distill gasoline from one chamber to the second.
The gear type uses two gears mounted one inside the other. The internal gear is smaller and follows the eccentric path. Due to this, there is a chamber between the gears, in which the fuel is captured from the supply channel and pumped into the exhaust channel.
Gear pump
Roller and gear types of electric petrol pumps are less common than centrifugal ones, they are also turbine ones.
Centrifugal pump
This type of fuel pump arrangement includes an impeller with a large number of blades. When rotating, this turbine creates vortexes of gasoline, which ensures its suction into the pump and further pushing into the line.
We looked at the device of the fuel pumps in a slightly simplified way. Indeed, in their design there are additional intake and pressure reducing valves, the task of which is to supply fuel in only one direction. That is, gasoline that has entered the pump can only return to the tank through the return line, having passed through all the constituent elements of the power system. Also, the task of one of the valves is to block and stop injection under certain conditions.
Turbine pump
As for the high-pressure pumps used in diesel engines, the principle of operation is radically different there, and you can find out in detail about such nodes of the power system here.
The fuel pump (abbreviated as fuel pump) is designed to perform the following functions - supplying a combustible mixture under high pressure to the fuel system of the internal combustion engine, as well as regulating its injection at certain times. This is why the fuel pump is considered the most important device for diesel and gasoline engines.
Mostly injection pumps are used, of course, in diesel engines. And in gasoline engines, injection pumps are found only in those units on which a direct fuel injection system is used. At the same time, the pump in a gasoline engine works with a much lower load, since such a high pressure as in a diesel engine is not required.
The main structural elements of the fuel pump are a plunger (piston) and a cylinder (sleeve) of a small size, which are combined into a single plunger system (pair) made of high-strength steel with great precision.
In fact, the manufacture of a plunger pair is a rather difficult task that requires special high-precision machines. For the whole Soviet Union there was, if memory serves, only one plant where plunger pairs were manufactured.
How plunger pairs are made in our country today can be seen in this video:
A very small gap is provided between the plunger pair, the so-called precision mating. This is perfectly shown in the video, when the plunger enters the cylinder very smoothly, hovering under its own weight.
So, as we said earlier, the fuel pump is used not only for the timely supply of the combustible mixture to the fuel system, but also for distributing it through the nozzles into the cylinders in accordance with the type of engine.
The injectors are the connecting link in this chain, so they are connected to the pump by pipelines. The injectors are connected to the combustion chamber with a lower atomizing part equipped with small holes for efficient fuel injection with its further ignition. The advance angle allows to determine the exact moment of injection of the vehicle into the combustion chamber.
Depending on the design features, there are three main types of injection pumps - distribution, in-line, main.
This type of high pressure fuel pump is equipped with plunger pairs located next to each other (hence the name). Their number strictly corresponds to the number of working cylinders of the engine.
Thus, one plunger pair supplies fuel to one cylinder.
The vapors are installed in a pump casing with inlet and outlet channels. The plunger is started using a camshaft connected, in turn, to the crankshaft, from which rotation is transmitted.
The camshaft of the pump, when rotated by the cams, acts on the plunger pushers, forcing them to move inside the pump bushings. In this case, the inlet and outlet openings are opened and closed alternately. When the plunger moves up the sleeve, the pressure required to open the discharge valve is created, through which the pressurized fuel is directed through the fuel line to a specific injector.
The moment of fuel supply and the adjustment of its amount required at a particular point in time can be carried out either by means of a mechanical device or by means of electronics. Such an adjustment is needed to adjust the fuel supply to the engine cylinders depending on the crankshaft speed (engine speed).
Mechanical control is provided through the use of a special centrifugal type clutch, which is attached to the camshaft. The principle of operation of such a clutch is enclosed in weights that are inside the clutch and have the ability to move under the action of centrifugal force.
The centrifugal force changes with an increase (or decrease) in the engine speed, due to which the weights either diverge to the outer edges of the clutch, or again approach the axis. This leads to a displacement of the camshaft relative to the drive, which is why the operating mode of the plungers changes and, accordingly, with an increase in the engine speed, early fuel injection is provided, and late, as you guessed it, with a decrease in speed.
In-line fuel pumps are extremely reliable. They are lubricated with engine oil from the engine lubrication system. They are not at all picky about the quality of the fuel. To date, the use of such pumps, due to their bulkiness, is limited to trucks of medium and large carrying capacity. Until about 2000, they were also used on light diesel engines.
Unlike an in-line high-pressure pump, a distribution injection pump can have either one or two plungers, depending on the engine volume and, accordingly, the required volume of fuel.
And these one or two plungers serve all the engine cylinders, which can be 4, 6, 8, and 12. Due to its design, in comparison with in-line injection pumps, the distribution pump is more compact and weighs less, and at the same time is able to provide more uniform fuel supply.
The main disadvantage of this type of pump is their relative fragility. Distribution pumps are only installed in passenger cars.
Distribution injection pump can be equipped with different types plunger drives. All these types of drive are cam and are: end, internal, external.
The most effective are end and internal drives, which are devoid of loads created by fuel pressure on the drive shaft, as a result of which they serve a little longer than pumps with an external cam drive.
By the way, it is worth noting that imported pumps from Bosch and Lucas, which are most often used in the automotive industry, are equipped with an end drive and an internal drive, and the external drive is provided by pumps of the ND series of domestic production.
End cam drive
In this type of drive used in Bosch VE pumps, the main element is a distribution plunger, designed to pressurize and distribute fuel in the fuel cylinders. In this case, the distributor plunger performs rotational and reciprocating movements during rotational movements of the cam washer.
The reciprocating movement of the plunger is carried out simultaneously with the rotation of the cam washer, which, leaning on the rollers, moves along the stationary ring along the radius, that is, as if it runs around it.
The action of the washer on the plunger provides high fuel pressure. The return of the plunger to its original state is carried out thanks to the spring mechanism.
The distribution of fuel in the cylinders occurs due to the fact that the drive shaft provides rotational movements plunger.
The amount of fuel supplied can be provided using an electronic (solenoid valve) or mechanical (centrifugal clutch) device. Adjustment is carried out by turning a fixed (non-rotating) adjusting ring through a certain angle.
The pump operation cycle consists of the following stages: injection of a portion of fuel into the supra-plunger space, pressure build-up due to compression and distribution of fuel among the cylinders. Then the plunger returns to its original position and the cycle is repeated again.
Internal cam drive
The internal drive is used in rotary-type distribution injection pumps, for example, in pumps Bosch VR, Lucas DPS, Lucas DPC... In this type of pump, the supply and distribution of fuel is carried out by means of two devices: a plunger and a distributor head.
The camshaft is equipped with two oppositely located plungers, which ensure the fuel injection process, the smaller the distance between them, the higher the fuel pressure. After building up the pressure, the fuel rushes to the injectors through the channels of the distributor head through the pressure valves.
The fuel supply to the plungers is provided by a special booster pump, which may differ depending on the type of its design. It can be either a gear pump or a rotary vane pump. The booster pump is located in the pump housing and is driven by the drive shaft. Actually, it is installed directly on this shaft.
We will not consider a distribution pump with an external drive, since, most likely, their star is close to sunset.
This type of fuel pump is used in the Common Rail fuel supply system, in which fuel is first accumulated in the fuel rail before being supplied to the injectors. The main pump is capable of providing a high fuel supply - over 180 MPa.
The main pump can be single, double or triple plunger. The plunger drive is provided by a cam washer or shaft (also a cam, of course), which rotate in the pump, in other words, rotate.
In this case, in a certain position of the cams, the plunger moves downward under the action of the spring. At this moment, the compression chamber expands, due to which the pressure in it decreases and a vacuum is formed, which forces the intake valve to open, through which the fuel passes into the chamber.
Raising the plunger is accompanied by an increase in intra-chamber pressure and the closing of the intake valve. When the pressure to which the pump is set is reached, the exhaust valve opens, through which fuel is pumped into the rail.
In the main pump, the fuel supply process is controlled by a metering fuel valve (which is opened or closed by the required amount) using electronics.
Any car engine has a power system that mixes the components of the combustible mixture and supplies them to the combustion chambers. The design of the power system depends on what fuel the power plant operates on. But the most common is a gasoline-powered unit.
In order for the power system to be able to mix the components of the mixture, it must also receive them from the container in which the gasoline is located - the fuel tank. And for this, a pump is included in the design to provide gasoline. And it seems that this component is not the most important, but without its work, the engine simply will not start, since gasoline will not enter the cylinders.
Two types of gasoline pumps are used on cars, which differ not only in design, but also in the place of installation, although they have the same task - to pump gasoline into the system and ensure its supply to the cylinders.
By design type, gasoline pumps are divided into:
A mechanical type gasoline pump is used on. It is usually located on the head of the power unit, since it is driven by the camshaft. Fuel is pumped into it due to the vacuum created by the membrane.
Its design is quite simple - a membrane (diaphragm) is located in the body, which is spring-loaded from below and along the central part is attached to a rod connected to a drive lever. In the upper part of the pump there are two valves - inlet and outlet, as well as two fittings, one of them draws gasoline into the pump, and from the second it goes out and enters the carburetor. The working area for the mechanical type is the cavity above the membrane.
The gas pump works according to this principle - there is a special eccentric cam on the camshaft, which drives the pump. During engine operation, the shaft, rotating, with the top of the cam acts on the pusher, which presses on the drive lever. That, in turn, pulls down the stem together with the diaphragm, overcoming the force of the spring. Because of this, a vacuum is created in the space above the membrane, due to which the intake valve comes off and gasoline is pumped into the cavity.
As soon as the shaft turns, the spring returns the tappet, drive arm and diaphragm together with the stem. Because of this, pressure rises in the cavity above the membrane, due to which the inlet valve closes and the outlet valve opens. The same pressure pushes gasoline out of the cavity into the outlet and it flows into the carburetor.
That is, all the work of a mechanical type of a non-pump is built on pressure drops. But we note that the entire carburetor power system does not require high pressure, therefore the pressure that the mechanical fuel pump creates is small, the main thing is that this unit provides the required amount of gasoline in the carburetor.
Such a gas pump works constantly while the engine is running. When the power unit stops, the gasoline supply stops, since the pump also stops pumping. In order for there to be enough fuel to start the engine and its functioning until the system is filled up due to the vacuum, there are chambers in the carburetor, into which gasoline is poured even during the previous operation of the engine.
In injection fuel systems, gasoline is injected by injectors, and for this it is necessary that the fuel comes to them already under pressure. Therefore, the use of a mechanical type pump is not possible here.
An electric fuel pump is used to supply gasoline to the fuel injection system. Such a pump is located in the fuel line or directly in the tank, which ensures the injection of gasoline under pressure into all components of the power system.
Let's just mention the most modern injection system - with direct injection. It works on the principle of a diesel system, that is, gasoline is injected directly into the cylinders at high pressure, which a conventional electric pump cannot provide. Therefore, such a system uses two nodes:
But we will not consider the high-pressure fuel pump for now, but we will walk through the usual electric fuel pumps, which are located either near the tank and are cut into the fuel line, or are installed directly into the container.
There are a large number of species, but three types are most widespread:
Rotary roller electric pump refers to pumps that are installed in the fuel line. Its design includes an electric motor, on the rotor of which a disk with rollers is installed. All this is placed in the supercharger cage. Moreover, the rotor is slightly offset in relation to the supercharger, that is, there is an eccentric arrangement. Also, the supercharger has two outputs - through one gasoline enters the pump, and through the second it leaves.
It works like this: when the rotor rotates, the rollers pass through the inlet zone, due to which a vacuum is formed and gasoline is pumped into the pump. Its rollers capture and transfer to the outlet area, but previously, due to the eccentric arrangement, the fuel is compressed, which is what the pressure is achieved.
Due to the eccentric movement, a gear-type pump also works, which is also installed in the fuel line. But instead of a rotor and a supercharger, it has two internal gears in its design, that is, one of them is placed inside the second. In this case, the internal gear is the leading one, it is connected to the shaft of the electric motor and is displaced relative to the second - the driven one. During the operation of such a pump, fuel is pumped by the teeth of the gears.
But on a car, a centrifugal electric fuel pump is most often used, which is installed directly into the tank, and the fuel line is already connected to it. Its fuel supply is carried out due to the impeller, which has a large number of blades and is placed inside a special chamber. As this impeller rotates, vortexes are created, which help gasoline to be sucked in and compressed, which provides pressure before it enters the fuel line.
These are simplified diagrams of the most common electric petrol pumps. In reality, their design includes valves, contact systems for connecting to the on-board network, etc.
Note that already during the start of the injection power plant, the system should already contain fuel under pressure. Therefore, the electric fuel pump is controlled by an electronic control unit, and it turns on in operation before the starter is triggered.
All fuel pumps have a fairly long service life due to their relatively simple design.
In mechanical parts, problems are rare. They arise most often due to a rupture of the diaphragm or wear of the drive elements. In the first case, the pump stops pumping fuel altogether, and in the second, it supplies it in insufficient quantities.
It will not be difficult to check such a gas pump, it is enough to remove the top cover and assess the condition of the membrane. You can also disconnect the fuel line from the unit from the carburetor, lower it into a container and start the engine. In a serviceable element, fuel is supplied in uniform portions with a sufficiently powerful jet.
In injection engines, a malfunction of the electric fuel pump has certain signs - the car does not start well, a drop in power is noticeable, and interruptions in the operation of the engine are possible.
Of course, such signs can give malfunctions in different systems, therefore, additional diagnostics will be required in which the pump performance is checked by measuring the pressure.
But the list of malfunctions due to which this unit does not work correctly is not so much. So, the pump may stop working due to strong and systematic overheating. This happens due to the habit of pouring small portions of gasoline into the tank, because the fuel acts as a coolant for this unit.
Refueling with low-quality fuel can easily lead to malfunctions. The impurities and foreign particles present in such gasoline, getting inside the unit, lead to increased wear of it component parts.
Problems can also arise through the electrical part. Oxidation and damage to the wiring can result in insufficient power being supplied to the pump.
Note that most of the malfunctions that occur due to damage or wear of the components of the gas pump are difficult to eliminate, therefore, often if its performance is broken, it is simply replaced.
