Car fuel pump - types, structure, fault checking

The fuel pump is one of the most important components of the engine power system. A pump malfunction leads to interruptions in the operation of the internal combustion engine, failures when pressing the gas, or even problems with starting. Let's look at the design and operating principle of fuel pumps for injection and carburetor engines; Let's talk about breakdowns and diagnostic methods.

According to their operating principle, fuel pumps (FP) of gasoline internal combustion engines are divided into 2 types:

• electrical;
• mechanical.

During engine operation, the fuel pump is used to pump fuel from the tank to the carburetor or fuel rail with injectors. On cars with direct injection and a high-pressure fuel pump (HPF), the fuel pump is used as a booster section.

Where is the fuel pump located, the purpose of the device

The location of the device responsible for the uninterrupted delivery of energy in operating mode depends on its type.
Mechanical ones are used on cars with carburetors, and also as an auxiliary system for diesel vehicles. To create an active and at the same time effective vacuum, the function of controlling the fuel pumping mode is transferred to the engine camshaft. Even car owners who do not have special knowledge will always accurately tell you where the mechanical fuel pump is located. When troubleshooting or replacing this unit, look for this unit in the area where the engine is located. Electrically driven fuel delivery systems are driven directly from the battery or generator. This removes the restriction on the location of this element. Depending on the designer’s design, superchargers can be located in the fuel tank area or in the engine compartment. The design of the fuel pump depends on a number of factors. These include the assigned functions, expected dynamics and engine power.

Connection diagram

The mechanical fuel pump is mounted very simply - in the provided mounting location. After installation, all that remains is to connect the fuel supply line hose to the inlet and outlet ports, after which the unit is completely ready for operation.

As for electric pumps, two connection schemes are practiced on modern cars: Long fuel supply ring - return of unused fuel from the injectors back to the tank. Short ring – return of unused fuel to the tank directly from the fuel pump.

Fuel pump drive

The VAZ 2107 fuel pump operates from a pusher (rod) and an eccentric located on the shaft of auxiliary devices (“piglet”, intermediate shaft), which is driven by the timing mechanism through a gear. Auxiliary devices include distributor, oil and fuel pumps.

Operating principle

The drive works as follows:

• the intermediate shaft rotates via a timing chain;
• the eccentric acts on the rod and pushes it;
• the rod presses the fuel pump lever, ensuring its operation.

Fuel pump drive malfunctions

As the fuel supply unit wears out, problems may occur that affect the performance of the latter.

Rod wear

The main sign of a worn-out rod is that the car does not reach the required speed. If the car accelerates, but, having gained speed to a certain value, does not develop it anymore, the reason is precisely the wear of the rod. Recently, the pusher has been made from such low-quality metal that it leads to wear out literally after 500–1000 km. The edge of the rod on the eccentric side is simply flattened, which indicates the need to replace the part.

Rod wear directly affects the performance of the fuel pump

The fuel pump rod should be 82.5 mm long.

Features of work

The distinctive properties of energy supply systems depend on the structural assembly. The drive unit contains rotary and gear pumps. Centrifugal devices typical for foreign cars should be looked for in the gas tank. The classification often uses a division into remote mechanisms that are mounted directly on the car body. Submersible structures are used inside tanks. With this design of the fuel pump, cooling of the moving parts is ensured and cases of idling are prevented. Additionally, the design of the supercharger includes sensors responsible for monitoring the level of gasoline and pressure in the supply system.

Unlike mechanical ones, electric models receive a signal to operate not from the camshaft, but from the engine control unit. A special relay is responsible for turning it on, which works synchronously with the ignition system. The pressure in the injection system can reach 0.4 MPa for gasoline and 0.7 MPa for diesel engines.

Classification and design of fuel injection pump

Pump sections that provide high fuel pressure for a diesel engine are of three types:

• In-line mechanisms - plunger pairs for each cylinder;
• Distribution, for passenger cars, more compact;
• Main line, used in fuel supply systems.

The latest type of fuel injection pump belongs to a new generation of systems and is controlled by a computer. An injection engine should not be confused with a high-pressure fuel pump, since this is primarily an injection system.

Depending on the type of plunger drive, fuel pumps are pneumatic, hydraulic and mechanical.

Mechanical and electric fuel pump

The fuel pump is the most important element of the fuel system. Its main task is to deliver fuel from the fuel tank at the rear of the car to the metered supply system in the engine compartment. Such a system is considered to be a carburetor or injector. The fuel pump can be represented by either a mechanical design or an electric fuel pump.

Mechanical fuel pumps have found their application in cars with a carburetor and provide fuel supply under low pressure. Electric fuel pumps are used in cars with fuel injection, as they are responsible for supplying fuel at high pressure and maintaining operating pressure in the system.

A mechanical fuel pump is mounted outside the fuel tank or near the carburetor, since there is no need to create high pressure in the fuel supply system. The electric fuel pump must be located inside the fuel line or fuel tank.

There is also a scheme for installing two fuel pumps at once. One fuel pump is installed in the tank and works with large volumes of fuel, pumping it under low pressure. Another fuel pump operates with a small volume of fuel and creates high pressure in front of the injection system. This pump is called a high pressure fuel pump. It is often located in the engine compartment near the power plant or directly on it.

It is worth noting that carburetor engines are considered obsolete, having long given way to more productive, economical and environmentally friendly fuel injection engines. There are a number of models where the electric pump is controlled by the ECU. The system takes into account the position of the throttle valve, the quality of the fuel-air mixture and the composition of the exhaust, thereby simultaneously adjusting the operation of the fuel pump.

Electric fuel pumps of the most modern type, while maintaining high pressure, exhibit excessive noise during operation and tend to heat up quickly. This determined their location in the fuel tank. The fuel is cooled by the gas pump itself, and the walls of the gas tank significantly absorb noise from the operation of the device.

Types of fuel pumps

Current models are equipped with both mechanical and electrical fuel pumps. Mechanical pump

found in carburetor cars,
electric fuel
injection pump, where fuel enters the car engine under pressure.

The mechanical gasoline pump is located outside the gas tank, but the electric one, on the contrary, is located inside it. There are cars in everyday use that have 2 fuel pumps installed. The mechanical unit operates under low-frequency pressure because the carburetor and fuel pump are located close to each other.

Mechanical design

A mechanical fuel pump consists of:

• covers;
• mesh filter;
• upper part of the body;
• top plates;
• working diaphragms;
• spacers;
• safety diaphragm;
• bottom plates;
• rod;
• return spring;
• lower part of the body;
• lever for manual pumping;

This design forms a chamber that has inlet and outlet valves. These valves are located in the upper part of the mechanical fuel pump housing. Such valves are textolite washers, which are pressed by small springs to brass valve seats.

Operating principle

The special drive lever of a mechanical fuel pump moves up and down all the time, but the diaphragm is moved downwards by the lever only when the fuel pump chamber needs to be filled. The diaphragm is pushed back up using a return spring. This is how the process of supplying fuel to the carburetor occurs.

If you look at the operation of a mechanical fuel pump more closely, you should take into account the slight difference between rear-wheel drive vehicles and front-wheel drive models. A car with rear drive wheels has an eccentric located on the drive shaft. This element exerts an impact on the pusher. Front-wheel drive models have a similar eccentric, but it is already located on the engine camshaft.

The pusher presses the lever, and the lever already presses the balancer. This balancer is located at the bottom of the fuel pump housing. The balancer overcomes the resistance of the spring and pulls down the rod with the diaphragms of the fuel pump. In this way, vacuum is achieved. Fuel passes through the inlet fitting, and the inlet valve allows fuel into the cavity above the diaphragms.

Next, the eccentric jumps off the pusher. The lever, balancer and rod with diaphragms are released. The pressure spring forces the rod with the diaphragms to move upward, thereby creating pressure in the working chamber of the fuel pump. Under the resulting pressure, the intake valve closes and the exhaust valve opens. Through this valve, fuel enters the outlet fitting, then continues to move along the connecting hose and penetrates the carburetor float chamber. More information about the carburetor can be found in the article on fuel supply devices.

If you manually pump fuel on a mechanical fuel pump, then the pumping lever on the pump body through the cam immediately affects the balancer and the rod with the diaphragms. The pusher is not used in this case.

When the float chamber in the carburetor is completely filled, then the needle valve will no longer allow fuel to pass there, and the pump will operate in standby mode. The point is that the pressure from the movement of the diaphragms in the pump body is still not able to overcome the resistance of the needle valve.

Multi-plunger injection pumps and their design features

Each section of the system has special pushers. At the beginning of the power stroke, a certain amount of fuel enters the plunger through the inlet port. At the end of the stroke, the supply channel closes, the cylinder creates pressure under which fuel is pumped to the nozzle for subsequent spraying into the cylinder block.

Peculiarities:

• In a row arrangement, pairs of plungers are located side by side;
• With a V-shaped arrangement of cylinders, pairs of plungers are in two rows.

How distribution injection pumps work

The fuel pumps that replaced the carburetor engine have a longer service life and improved drive. Distribution systems often have one plunger, which provides efficient supply to the engine, but at the same time wears out quickly and requires service work.

The pusher drive is made in the form of a cam mechanism, rotary or mechanical. There are systems with external drive. When a push is received from the cam, the plunger is pushed upward with a subsequent increase in pressure. Thus, the high-pressure fuel pump supplies gasoline or diesel to the injectors through the distributor channel for subsequent delivery to the cylinder blocks.

Electrical device

The electric fuel pump is structurally similar in some parts to a mechanical one in a number of elements. Such a pump operates thanks to a special core, which is pulled into the solenoid valve until the contacts for supplying electric current are disconnected.

Turning the key in the ignition before starting is a signal to the car's on-board computer. At this stage, electric current is already supplied to the fuel pump. The engine has not yet been started, but in a couple of seconds the electric motor inside the fuel pump already raises the pressure in the fuel system to operating pressure. This is why it is recommended to wait 2-3 seconds before turning the starter and starting the engine.

If the ECU does not receive a signal that the engine has been started successfully, then the fuel pump is turned off automatically. This is done for security purposes. Some cars are designed so that the fuel pump starts when the driver's door is opened.

An electric fuel pump is capable of creating fuel pressure at around 0.3-0.4 MPa, and in engines with a direct injection system this figure reaches 0.7 MPa. In this article we will not talk in detail about the high-pressure fuel pump (HPF) for diesel and gasoline engines with direct injection. Read about such a system in the corresponding section of the site.

A special feature of the gasoline electric pump is the use of a modular system in its design. This is due to its direct contact with the fuel. Key elements of the pump also include a fuel intake, a fuel filter and a sensor that indicates fuel consumption.

An electric pump has a diaphragm that moves up and down. The result is that a vacuum is created above the diaphragm on the downward stroke. This allows the suction valve of the electric pump to open. Through such a valve, gasoline passes through the filter and ends up in the chamber above the diaphragm. When the diaphragm moves upward, the resulting pressure closes the inlet valve and opens the discharge valve, which pushes the fuel further into the system.

Essential elements

The electric fuel pump consists of:

• cameras;
• intake and exhaust valve;
• diaphragms;
• return spring;
• solenoid valve;
• core;
• electrical contacts;

The check valve is responsible for shutting off the fuel system when the engine is stopped. The pressure reducing valve maintains high operating pressure in the fuel system.

Main faults and service life

The average service life of key system elements is 200,000 kilometers. The resource can be compared with the overhaul interval of a gasoline engine with a fuel injection pump, when the car requires complex intervention. The main malfunctions of pumps for supplying and maintaining pressure in the system can be classified in two areas:

• Violations in the control unit. The unit receives incorrect signals, which directly affects the responsiveness of the car when driving;
• Mechanical wear of individual parts. Due to the rather complex circuit of the fuel pump, it is unsuitable for restoration (disassembly and diagnostics will be expensive). It’s easier and cheaper to buy a new part for later replacement.

Types of fuel pumps

There are three main types of electric fuel pumps - gear, centrifugal and roller.

Gear

In a gear pump, fuel is supplied by a rotor (inner gear, movable), which is located eccentrically relative to the stator (outer gear, stationary). As the rotor rotates, the sides of its teeth form small chambers that change size depending on where the stator passes.

At the inlet, the chambers have a maximum size and suck in fuel due to the discharge into themselves. As it rotates relative to the stator, the chamber decreases in size, thereby ensuring the supply and injection of fuel at the outlet of the pump.

Roller

A similar principle is used in a roller pump, in which the fuel supply is also carried out due to the eccentric arrangement of a rotating rotor with movable rollers and a stationary stator. The rollers move in special recesses in the rotor. The space that appears between the rotor and the roller is completely filled with fuel at the moment when the roller, under the influence of centrifugal force, strives to break out of the rotor as much as possible.

Continuing to rotate, the rotor moves the rollers relative to the stator, the shape of which changes, forcing the rollers to be pressed against the center of the rotor's axis of rotation and thereby compressing the fuel. At the outlet, an additional condition is created in which the outlet port opens and high pressure fuel is removed from the pump.

Centrifugal

In a centrifugal pump, fuel supply is ensured using an impeller, which is equipped with special blades around the entire perimeter. The rotation of the impeller occurs inside a cavity equipped with two channels - suction and discharge. The rotational movements of the blades provide a vortex flow of fuel, thereby achieving an increase in pressure.

If, due to their design features, gear and roller pumps are mounted directly into the fuel line, then the centrifugal pump is located in the fuel tank. In modern fuel systems, preference is given to a centrifugal pump, which is much less noisy and provides a smoother (without pulsations) flow of supplied fuel, although it has limitations in performance and pressure created.

The operation of the electric heat pump is controlled by the internal combustion engine control unit. The fuel pump begins its work in parallel with the ignition being turned on, however, there are cars in which the pump is activated when the driver's door is opened (even before the ignition key is inserted or the start button is pressed).

The electric pump is capable of maintaining a rather narrow, but sufficient for normal engine operation, operating pressure range, which is regulated by changing the voltage and using a safety valve that limits the maximum permissible pressure in the system.

Vacuum

The operation of the vacuum pump is based on a conventional fuel pump of a carburetor engine. The only difference is in the drive, but the mechanical part itself is almost identical.

There is a membrane dividing the working module into two chambers. In one of these chambers there are two valves - inlet (connected by a channel to the tank) and outlet (leading to the fuel line, which supplies fuel further into the system).

This membrane, when moving forward, creates a vacuum in the chamber with valves, which leads to the opening of the inlet element and the pumping of gasoline into it. During 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.

As for 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 that arises 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 membrane to its original position (return movement). The supply of impulses to the electrical part is controlled by the electronic injector control unit.

avtoexperts.ru

Any engine is equipped with a fuel system, one of the important parts of which, regardless of modifications, is the fuel pump. Before understanding the device and principle of operation, two main types should be distinguished:

• Electric (most common).

• Mechanical (found in carburetor cars).

1. An electric fuel pump is installed in modern fuel-injected cars. It is often placed in the tank or next to it, in the fuel line. So that the unit has the opportunity to cool, since they get very hot during operation.

Fuel pump assembly Lada Priora

The operation of the electric fuel pump is fully controlled by the ECU. When the driver turns on the ignition, the ECM sends a signal to start the pump. Next, an electric motor located inside the pump with rollers or impeller blades generates the required pressure. Due to these actions, the mixture enters the intake zone, and then into the outlet, then sent through the fuel line.

The fuel line “rests” on the so-called ramp, where the fuel is directed under pressure. By the way, before entering the ramp, the “fuel” passes through another filter, in addition to the mesh filter, located directly on the gas pump. Once in the ramp, the fuel is distributed among the injectors. Then, depending on the opening time of the injectors, the required amount of gasoline is injected into the cylinders.

Fuel system

By the way, depending on the type of system, there may be one or several injectors per cylinder.

The role in determining the duration of opening of the injectors and, accordingly, the required volume of fuel is assigned to the controller (ECU) and multiple sensors, for example, the throttle position sensor (TPS), the coolant temperature sensor (DTOS), the crankshaft position sensor (CPS), the knock sensor ( DD), oxygen sensor (OK), air flow sensor (MAF) or absolute pressure sensor (DAS), idle air control (IAC), which transmit data to the controller (ECU).

When the ECU stops sending signals or, conversely, does not receive impulses from sensors about the operation of the internal combustion engine, the relay stops powering the pump. Remember that the pump runs as long as the engine is running. Read below for specific examples of how a fuel pump works, depending on the modification.

Types and features of operation of electric fuel pumps:

• Gear. • Rotary roller. • Centrifugal.

The main differences between them are where exactly they are installed. The first two are similar, as they are mounted directly into the fuel line. It looks like this: discs with rollers are installed on the rotor of the electric motor, all of this is placed in the so-called “cage”, from which there are respectively two outputs. When rotating, the rollers capture the inlet zone, again a vacuum zone is formed, which is why “fuel” is pumped in. Further rotating, the rollers, capturing fuel, move to another outlet (exhaust zone). Pressure arises for the reason that the rotor itself is placed in the “cage” disproportionately, due to which there is a certain displacement, the so-called eccentric arrangement. The gear type works similarly, where gears are installed instead of rollers.

This fuel module is located in the tank

But, in the modern world, you can often find a third type of mechanism, like a centrifugal one. Such systems are mounted directly into the tank, and a pipeline is already connected to it. Feeding occurs due to the rotation of an impeller with blades, which is placed in a special “chamber”. When the impeller rotates, turbulence is formed, causing gasoline to be sucked in and then enter the fuel line under pressure. And then, accordingly, into the injector.

2. As for mechanical fuel pumps, they can now be found on old carburetor cars. Such units are often located in the engine compartment, above the head. This is due to the fact that instead of an electric motor (as in the previous version), the mechanisms are driven by a “camshaft”.

Mechanical fuel pump Audi 80

The principle of operation is as follows: on the “camshaft” there is a cam, which, when the shaft rotates, acts on the pump pusher. The latter acts on the drive lever, which pulls the rod where the membrane is attached. In this case, when the rod lowers, a vacuum zone is created, causing the inlet valve to open and the mixture to be pumped in.

Device

In the reverse order, the rod returns, the pressure increases, the inlet valve closes, and the outlet valve, on the contrary, opens. Then, under pressure, the mixture is poured into the outlet fitting, from where it enters the carburetor. The latter, in turn, mixes fuel and gasoline in the mixing chambers and directly supplies this mixture to the cylinders, through special fittings and valves. For clarity, carefully study the figure.

Malfunctions

As a rule, the service life of gasoline pumps is long, given their generally simple design. Types of faults can be divided into two groups:

• For mechanical.

• For electric ones.

So, in the first case, the problems are related to the fact that the membrane has torn or the drive parts have worn off (cam, drive lever), or the valves (inlet, exhaust) have failed. If the membrane is torn, then in principle fuel will not be supplied, because there will be no vacuum zone. In other cases, “fuel” arrives, but in insufficient quantities (jerks and engine stalling are possible).

The electric fuel pump is also quite reliable, but it also has malfunctions. So:

• Problems with wiring (dirty, rusty, damaged).

• Debris in the tank (dirt, water, rust) gradually penetrates into the fuel pump.

Dirty mesh in the fuel pump

• Natural causes (wear of internal parts of the mechanism).

• Problem with relay, fuse.

Why doesn't the fuel pump work and how to check?

There are many reasons why the device has stopped or there is a noticeable decline in operation; let’s look at the most common ones.

1. Damaged wiring. Three wires “fit” the pump: minus, plus and a wire to the fuel sensor. It's quite easy to check if it's working properly. Connect a 12 V light bulb to the external power supply of the device, if it lights up, you can look for the cause further.

Wiring

2. Fuse. It is located in the engine compartment, usually under the marking “FUEL PUMP”. Take it out and inspect for continuity of contact.

Chevrolet Lacetti fuel pump fuse

3. Relay. When the ignition is turned on, the pump relay makes a characteristic click immediately before starting (turns on) and after a few seconds (turns off) as the pump has created the required pressure. If such clicks are not observed, check it, similarly, for the condition of the contacts.

Fuel pump relay Citroen C4

4. The ground contact of the pump is usually located under the “tidy”. Sometimes problems with it are indicated by a fuel sensor that produces incorrect readings. Check and clean contacts if necessary.

5. Not enough pressure. Even if you hear the device working, it is not a fact that the required pressure is being delivered. To check, use a pressure gauge and measure the values ​​in the fuel rail. Often the average for a working pump is 3 atmospheres.

We measure the pressure in the fuel rail

Insufficient pressure indicates:

- faulty pressure regulator;

— filter contamination (when you press the gas, the pressure gauge needle rises slowly);

— fuel pump failure (the indicators do not increase when you press the accelerator).

6. Electric motor. If everything else has been checked, it's time to start diagnosing the motor. Often the terminals oxidize, causing contact to disappear; just clean them. But, if the terminals are clean, then you should connect the light bulb to the terminals of the electric motor. If the light comes on when you turn on the ignition, it means the motor is faulty.

Fuel pump electric motor

Conclusion

As a result, I would like to emphasize how important it is to monitor the condition of the fuel pump and filters, because they are the key to ensuring that the fuel system will last longer. Follow standard operating rules: do not use low-quality gasoline, drive less on an “empty” tank, monitor the condition of the wiring supplying the pump, etc.

Why is an electric pump better than a mechanical one?

ATTENTION! A completely simple way to reduce fuel consumption has been found! Don't believe me? An auto mechanic with 15 years of experience also didn’t believe it until he tried it. And now he saves 35,000 rubles a year on gasoline! Read more". The efficiency of an electric pump is clearly visible on diesel cars, where diesel fuel is supplied under high pressure, and on gasoline cars with a direct injection system.

Fuel is injected directly into the cylinders of the power unit. And in this case, a conventional mechanical pump simply will not be able to provide the required level of pressure

The efficiency of an electric pump is clearly visible on diesel cars, where diesel fuel is supplied under high pressure, and on gasoline cars with a direct injection system. Fuel is injected directly into the cylinders of the power unit. And in this case, a conventional mechanical pump simply will not be able to provide the required level of pressure.

Direct injection injectors use two pumps. The electric one is installed in the fuel tank, from where it pumps gasoline, and the second pump is the injection pump. The latter’s task is to increase the pressure of gasoline before it is directly supplied to the injectors.

The electric pump is capable of pumping an average of 1-2 l/min. Crazy efficiency, which is only possible at a pressure of 3-4 atm. To equalize the operating pressure to the desired performance level, a special regulator is used in the fuel rail. It's called RDD.

How to find out which fuel pump is on your car

Any more or less experienced driver is, of course, well aware of what type of gas pump his car is equipped with. As mentioned above, carburetor engines are equipped with mechanical fuel pumps installed in a specific location. However, sometimes carburetor engines are also equipped with electric pumps - this point needs to be clarified when buying a car, especially “hands-on”.

On cars with a fuel injection system, as well as with a direct injection system, exclusively electric fuel pumps are installed, which are located directly in the fuel tank.

Is it possible to repair a fuel pump yourself?

Mechanical fuel pumps, due to their simple design, are subject to repair - in fact, there is nothing special about them that can break. Most often the membrane fails, sometimes the rod. All this can be replaced, although most car enthusiasts prefer not to bother and buy a new pump - it is inexpensive and can be replaced in literally 10 minutes.

As for the electric fuel pump, it is not recommended to repair it, especially on your own. Theoretically, the electric fuel pump cannot be repaired - this is provided by the manufacturer. In practice, some craftsmen open the case and try to repair or replace damaged or failed parts. Such amateur activity is fraught with serious damage to the fuel system, so there is no point in experimenting, and it is better to purchase a new pump.

Signs of a fuel pump malfunction

In a mechanical fuel pump, malfunctions most often occur due to wear of the sealing gaskets and the formation of leaks between parts of the housing. As a result, the tightness of the structure is broken, air gets in, fuel stops getting into the carburetor and the engine stalls. A similar consequence is caused by membrane rupture and valve failure. At the same time, the car begins to move jerkily until the fuel supply stops completely.

On cars with mechanical and electronic injection, the signs of a fuel pump malfunction are slightly different, but they can be classified into certain groups:

1. The engine does not start. Rotation of the starter with dry spark plugs does not cause flashes in the cylinders. There is no pressure in the fuel line, or it is extremely low; the buzzing of the pump is not heard when the ignition is turned on or the starter is operating.
2. The engine does not start, although occasional flashes occur in the cylinders. There is pressure in the fuel line, but without a pressure gauge its value cannot be determined. The candles are dry.
3. The engine starts and idles normally, but pressing the accelerator causes it to stop. If you want, it is possible to raise the speed to medium, but attempts to start lead to the engine stalling. There is a black coating on the spark plugs, the operation of the fuel pump is characterized by a changing sound.
4. The engine starts, holds idle speed normally, and picks it up easily at neutral speed. When driving at medium and high speeds, a “twitching” is observed. It happens that after a certain mark on the tachometer the speed does not pick up, and the engine stops producing the required power under load. At the same time, the spark plugs are white, and by their appearance it seems that the car is ignited too early or has a lean mixture.

It is worth noting that the above symptoms of fuel pump malfunctions are also typical for other engine breakdowns, and they cannot be used to unambiguously diagnose a fuel pump malfunction. For example, speed also fluctuates if there is a problem with the air sensor, throttle valve, clogged injectors or poor quality fuel.

Possible causes of fuel pump malfunction

A mechanical fuel pump may fail for the following reasons:

1. If the integrity of the diaphragm is damaged.
2. After dirt accumulates under the valves.
3. When the filter is clogged.
4. When the spring loses its elasticity.
5. If the seal of the housing is broken.
6. Due to natural wear and tear of parts during operation.

The electric fuel pump of a modern car is quite reliable. Malfunctions in it arise only due to the influence of certain factors, among which the most common are the following:

1. Faulty wiring in the form of dirty, rusty, melted or damaged wires in the fuel complex interferes with the operation of the device and also limits the required current parameters, making it difficult to pump fuel.

2. Debris and foreign impurities in the fuel tank in the form of rust, dirt, water, mechanical particles that penetrate the fuel pump and cause its breakdown.

3. A clogged fuel filter with debris from the tank contributes to a sharp decrease in the pressure created by the pump and a deterioration in its operating parameters.

4. Driving a car for a long time with a small amount of fuel, during which the pump is not immersed, experiences significant overheating, quickly consumes internal lubricant and fails.

5. Natural wear of the rubbing parts of the pump.

How does a fuel pump work?

The electric pump seems to push the supplied fuel inside the car engine. Fuel pump device

in older car models it is such that their unit operates at a fixed speed. New models are designed in such a way that the speed of the unit depends on the motor. The electric fuel pump depends directly on the electrical system of the car, which takes into account indicators such as the aero-fuel ratio, throttle position, and the amount of exhaust emissions contained.

Such units begin to work when the electric motor starts. When you turn the ignition switch, the on-board computer is activated and a signal is given to start the fuel pump. When an electric charge is applied, the motor inside such a pump begins to rotate, thereby creating pressure in the fuel system. If there is no engine signal for more than a few seconds, the fuel pump will be automatically turned off.

How does a fuel pump work?

, is heard during the first moments of starting a car engine. Next, gasoline enters the fuel pump through a tube and exits through a one-way valve, and then passes through the fuel filter into the car engine. While the engine is running, the fuel pump will also work.

The design of the car's power system and the operation of the fuel pump

Electric fuel pumps push fuel into the engine. The operation of the electric fuel pump is controlled by the vehicle's electronic system, which takes into account throttle position, air-to-fuel ratio and exhaust emissions.

Since electric fuel pumps operate under pressure, they are quite noisy and heat up quickly. It is for this reason that they are placed in the fuel tank - the fuel cools the fuel pump and muffles noise.

How to check the fuel pump?

If the fuel pump does not start when the ignition is turned on, the check begins by looking for electrical problems:

1. Checking the fuse. To do this, find the fuse box, find out which one is responsible for the fuel pump (check the diagram) and inspect it for burns. It’s even better to immediately replace it with a known working one with the same characteristics and see if it works;
2. Checking the fuel pump control relay. It can be installed near the fuse box, injection control unit or other places. To check the pump relay, you need to remove and measure the winding resistance with an ohmmeter. If the indicator tends to infinity, then there is a cliff;
3. Check current supply. To do this, you need to get the fuel pump itself without disconnecting it from the power supply. Turn on the ignition and measure the voltage at the terminals; normally it should be 12-12.5 V. If the motor does not work, it will have to be replaced;
4. You can ring the fuel pump motor itself. Measure the resistance of the stator winding with an ohmmeter, first at the motor contacts for a break, then between the contact and the housing. If there is conductivity, it means that the stator winding is short-circuited to the housing;
5. If everything is normal, evaluate the condition of the mesh filter. Perhaps it is clogged to such an extent that it does not allow the required amount of gasoline to pass through, in which case it must be cleaned and used further;
6. Check the check valve, which prevents gasoline from returning back from the fuel line. Either test with a pressure gauge (the indicator should be no more than 0.3 MPa), or clean the valve and see how the engine operation changes;
7. And finally, check the gasoline pressure in the system. To do this, connect a pressure gauge to the fuel rail and measure the pressure with the engine off, idling and while driving. When the engine is turned on, the pressure gauge reading should be between 3-3.7 atm.

If the check shows that the fuel pump is faulty, it is not repaired, but replaced. All the elements are adjusted too finely to try to repair something without special equipment.

When buying a gas pump, it is better to give preference to good, well-known brands rather than a suspiciously cheap “confiscated” product. Then there is a chance that the new pump will last at least 100 thousand km and will not create problems.

Why does the fuel pump pressure drop, possible reasons

One of the most common reasons is lack of power supply to the fuel pump. The fuel pump pressure may also drop while driving, when the power supply suddenly stops and the engine simply stalls. An equally important indicator is the amount of fuel supply. That is, the fuel pump may hum (there is power), but not supply the required amount of fuel and not create the required pressure in the rail. The pressure gradually accumulates in the ramp and should be about 300 kPa. To check the pressure in the fuel rail, use a pressure gauge. Pressure indicators must correspond to the specific brand of car. For example, for injection models of VAZs, when the ignition is turned on, the norm is 3 atmospheres, at idle speed - 2.5, when the gas pedal is pressed - 2.5-3 atmospheres.

Using a pressure gauge, you can most likely determine the nature of the malfunction: failure of the rail pressure regulator, breakdown of the fuel pump, decrease in its performance as a result of exhaustion, contamination of the filters (fuel filter, fuel pump mesh). For example, if the filter is dirty, the pressure will increase very slowly or abruptly.

When the fuel pump pressure drops below normal, the engine may not start at all, or may start with difficulty, jerk, trip, operate unstably, with dips, etc. If the reason lies in the fuel pump and not in the fuel filter, then most likely the pump mesh is simply clogged. In this case, it will be enough to clean or replace it.

If there is a suspicion that the fuel pump is broken, this can be checked very simply. Just turn the ignition key and listen carefully to see if you can hear the hum of the pump. If you do not hear the characteristic humming sound of the unit running, there may be a problem with the power supply or wiring. It should be noted that in expensive brands of cars, for example, premium ones, it is impossible to hear the sound of a running pump due to high-quality sound insulation.

The list of possible reasons for a non-working fuel pump, and, accordingly, a drop in pressure, includes:

• Broken fuse. • Failure of the fuel pump relay. • Failure of the pump electric motor. • Oxidation of contacts, etc.

How to change a gasoline pump on carburetor engines

The procedure for replacing a fuel pump on carburetor cars is not complicated. First, you need to turn off the engine and let it cool to make repairs more comfortable. Then perform simple manipulations:

1. Remove the hoses from the inlet and outlet of the fuel pump.
2. Unscrew the two nuts that secure the pump housing to the motor.
3. Carefully remove the housing.
4. Remove the pump rod and remove the old gaskets.

Reassemble in the reverse order, change the rod if necessary and install a sufficient number of gaskets. It is important that the rod protrudes no more than 1.2 mm above the surface.

Filter and mesh of the electric fuel pump, why they are needed and how often they are changed

Fuel from the gas station usually needs additional cleaning. The injection system is especially sensitive to fuel quality. Fuel filters are used for additional cleaning. The cleaning process is carried out in two stages: first, rough cleaning - through the fuel pump mesh.

Large particles of rust and debris are filtered out here. The second stage is fine cleaning, which is performed by the fuel filter. In different car models, fine filters are installed in different places. Most often it can be found under the hood of a car.

The injection system requires very thorough cleaning of the fuel - from 5 micrometers. The pressure in such a system is quite high, so fuel filters are made of durable material or stainless steel.

replacing the fuel filter

The engine owner's manual should indicate how often the fuel filter needs to be changed. Most often, this procedure is carried out once every two years or after a certain mileage of the car. However, given the quality of fuel at domestic gas stations, it is recommended to change the filter at least once a year. During intensive use of the car, it is recommended to periodically check the fuel filter and, if necessary, change it immediately.

You can replace the filter at a service station or yourself - the procedure is simple. Before changing the fuel filter, it is necessary to relieve the pressure in the rail.

For this:

• Disconnect the minus terminal. • Remove the fuel pump relay. • Connect the terminals to the battery. • Start the engine and wait until it stalls.

Now you can remove the fuel filter. We pinch the latches on both sides of the filter with our fingers and carefully remove it. Remember - approximately 100 grams of fuel remains inside the filter and it can leak out. Next, we perform the steps in reverse order - install a new filter, disconnect the terminals, replace the relay, connect the terminals, start the engine. We check for leaks at the connection between the filter and the fuel hoses.

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It is very important to be able to determine when the filter is clogged. First of all, this can be signaled by poor engine starting; traction drops significantly; during sharp acceleration, the engine “chokes” and may stall. At idle, the engine runs unevenly; while driving, the engine lacks fuel if the speed exceeds 100 km/h.

How to check the fuel pump on an injector

Owners of fuel-injected cars know that when the ignition is turned on, the fuel pump motor turns on, pumping fuel from the gas tank to the engine begins, and a peculiar sound similar to a buzzing is heard.

If you suddenly notice that when you turn the ignition key, the fuel pump does not activate, then you will have to look for the causes of the malfunction. This could be electrical wiring, the pump itself, a relay, or a motor. It is better to look for the cause of problems in a certain sequence. First, check whether power is supplied to the fuel pump and so on, along the chain.

How to check the pressure in the fuel rail?

You will need a pressure gauge that measures pressure in the range from 7 to 10 atmospheres. If you choose a pressure gauge with a large margin, you risk getting less accurate measurement results. Specialized stores sell a kit for measuring pressure, but you can also design your own device.

If you want to assemble the device yourself, you will also need a hose with an internal diameter of 9 millimeters. You will also need plumbing tow, with which you can seal the connection between the pressure gauge and the tube. All parts are connected and tightened using a clamp. You will also need a car spool. Next you need to perform a series of actions:

1. Place the car on a level surface that is prevented from rolling, turn off the ignition and open the hood.
2. Check that the injection nozzles have access to the fuel rail.
3. Find the fuel pressure plug and remove it. Then you should unscrew the nipple using the spool.
4. Prepare an empty container (a regular bucket will do) and a clean rag. This is necessary to collect residual fuel, which under pressure can splash out in different directions. Therefore, take care of the safety of your skin (especially your face and eyes).
5. Connect the device to the fitting and begin checking the mechanism.

Checking the pressure in the fuel rail should occur in four operating modes of the power unit:

• when the ignition is on;
• at idle engine speed;
• code the fuel pressure regulator tube is reset;
• when the drain tube is compressed.

Electric fuel pumps

Here the system is more complex, because there are two types: submersible devices placed in the tank, and remote ones, fixed separately. Both are powered by an electric motor located directly in the pump. How to check the fuel pump?

Voltage

Take a regular tester, or if you don’t have one, a car light bulb with the wires attached. Now you need to detect your device. If the fuel pump is remote, it is located somewhere near the tank. If submersible, look for the output terminals (usually they are under the rear seat). Further:

• turn on the ignition;
• touch the voltmeter probes or wires from the lamp to the contacts;
• if the device readings correspond to 12-12.5 volts or the light comes on, it means that voltage is supplied to the pump.

Wiring

Assessing its condition is easy: take a pair of long wires and connect directly to the pump. If it “squeals”, consider that the cause of the malfunction has been found. And if not? Go ahead.

Fuse

Everything is clear here: you need to find where it is and replace it, or insert a bug. If the fuse blows, the problem is most likely related to the positive wire going to the fuel pump, which shorts to ground.

To find it, read the labels on the fuse box cover. Pull the part out of the socket. Just in case, you need to check the serviceability of the relay with the battery terminals removed. Wind a wire onto its plus and connect it to two points of the relay: “85” and “30”. Connect the negative electrode to the light bulb contact and the relay terminal “86”. The second wire from the lamp must be connected to pin “87”. If the lamp lights up, the relay is working properly. If you have a multimeter, connect its probes to terminals “85” and “86”. An infinitely high resistance indicates a winding burnout. But what to do when you find that the relay’s performance is zero, and there is nowhere to purchase the part? Just bridge its contacts “87” and “30”.

How to check fuel pump pressure

It happens that the device works, but the engine does not start. In this case, you need to check the pressure, which should be from 2.5 to 3.2 kg/sq.m. cm (check the operating instructions for your machine). When you press the accelerator, it rises by an average of 0.5 kg/sq.m. see. If this is not possible, try inspecting the coarse filter. To remove it, if the pump is a submersible type, remove the hatch by unscrewing the bolts. Next, check the fuel pipes for fuel leaks. Finally, replace the fine filter.

Diagnostics, who can diagnose the operation of the fuel pump, advice from the pros

Of course, the most accurate and high-quality diagnostics of a fuel pump, especially an electric one, can only be done at a specialized service station. However, some manipulations, especially if the machine is domestically produced, can be done independently.

The first thing you should check is the fuel pump fuse. Next, the fuel pump relay needs to be checked. To do this, check the presence of voltage at the control terminals, and touch the ground with the other end. The test is carried out using a multimeter or a test lamp, with a current consumption of no more than 0.25 A. If the fuse is working and the lamp does not light, you should look for the cause in the wiring and control unit.

The electric fuel pump is checked as follows: if the fuel pump is not removed, measure the voltage on its chip. The removed fuel pump is connected to a 12V source, for example, to a car battery.

Checking a mechanical fuel pump is extremely simple: remove the hose from the outlet fitting and press the manual pump lever several times. If fuel flows, the pump is working. In the case when manual pumping works, but no fuel is supplied while the engine is running, the reason is most likely a worn-out rod. Due to constant contact with the eccentric, the pump rod may “shorten” over time and simply not reach the lever. In this case, the part needs to be replaced - the fuel pump rod costs a penny and can be replaced in 10-15 minutes.

Car won't start after replacement

Car won't start after replacing fuel pump? This phenomenon is not uncommon. In many cases, this is not a problem. The car cannot start immediately because the pump takes time to pump up the pressure that was previously reduced. To bring the pressure to the optimal level, you need to turn on the ignition for 5 seconds so that the instrument panel lights up. Next, turn the engine with the starter. If it doesn't work on the first try, you should wait about a minute and try again.

If cranking the starter does not help start the engine, then one of the following reasons may be occurring:

• errors were made when assembling or connecting the BN;
• the new fuel module is faulty;
• the car's security system has gone down or a blockage has occurred;

When installing and connecting a new pump, failures of various types are possible: from malfunction of the valves on the fuel pump to breakage of contacts, terminals or connectors.

It is important to identify the exact nature of the problem and determine its type - electrical or mechanical. The simplest breakdown relates to the power supply to the fuel pump; it either exists or it doesn’t. If we are talking about an immobilizer or alarm system, then the anti-theft system can turn off the power supply to the BN, preventing the car from starting. Don't forget about filter clogging either. If the valves are stuck, the device can operate and produce characteristic sounds, but at idle.

The listed malfunctions prevent fuel from entering the ramp, so the engine cannot start. To clearly determine the cause, it is important to make sure that there is no gasoline in the rail. Next, it is recommended to dismantle and connect the BN from the dimensions or batteries directly. This method is considered the fastest for checking the device.

Preventing fuel pump breakdowns

The best prevention for long-term operation of the fuel pump is its careful and proper operation, as well as compliance with the following rules:

1. All scheduled vehicle repairs must be accompanied by the replacement of all fuel filters.
2. It is necessary to monitor and ensure the cleanliness of the fuel tank and filters, as well as monitor the quality of the fuel being refilled (the absence of water, sand and other impurities in it).
3. Eliminate the possibility of water getting into the fuel tank.
4. Protect the fuel pump housing from mechanical stress that causes dents and cracks that contribute to the development of corrosion processes.

Scheduled maintenance of the fuel pump, what work is done at this time

As you know, the best prevention is careful treatment and proper operation of the unit. The following recommendations will extend the life of the fuel pump:

At each scheduled car repair, change the fuel filter and fuel pump strainer. Refuel with quality fuel. Clean the fuel tank regularly - water and rust can accumulate in the tank, which can impair the performance of the pump and fuel system. Water in the tank can cause corrosion on the metal parts of the fuel pump.

Fuel pump service life

The service life of a fuel pump depends on its design and the materials from which it is made. Depending on the model of the device, the fuel pump will work without interruption for a period of 100 to 200 thousand kilometers of the car.

The pump fails for two main reasons:

• untimely replacement of fuel filters. Moreover, some pay attention only to the fine cleaning element, but the cleanliness of the mesh, which is installed directly on the pump itself, deserves no less attention. When the pump tries to create pressure through a dirty filter, it gets hotter. Timely maintenance will extend the life of the pump;
• The fuel level in the gas tank is often low. Because of this, the device does not receive proper cooling, so the risk of overheating increases significantly.

Also pay attention to the video on how to restore some pumps:

Main fuel injection pumps of the Common Rail system

In such pumps, which work primarily with diesel engines, fuel is collected in a special ramp before being pumped into the injectors. The intermediate accumulator in the injection pump is used to generate sufficient pressure (but not excessive), as well as to compensate for losses caused by the failure of individual injectors. Depending on the required level of injection force, designers can install one, two or three plungers in such systems.

Methods for dispensing fuel into the injection pump

The cyclic supply of diesel, in contrast to injection and carburetor gasoline pumps, ensures more accurate energy consumption. Due to an additional device - a bypass valve, excess fuel is removed at excess pressure.

The classification uses three types of devices:

• With throttling at the moment of fuel intake;
• With cut-off function;
• With a combination of dosages.

Fuel volume control can be mechanical (spring) or electronic.