How to check the fuel pump? 4 signs of breakdown and 5 inspection steps + video

Signs of a faulty fuel pump:

You may have a fuel pump failure problem if your car jerks at high speeds
The fuel pump may be faulty if you lose power when accelerating
Loss of power when lifting or towing a load
Failure of the fuel pump may cause the engine to not start.

In mechanical pumps, a diaphragm mounted on the outside of the fuel tank expands and contracts, creating a low-pressure system that forces fuel out of the tank and into the engine.

Electronic pumps are typically located inside the fuel tank and use electromagnetic motors to force fuel into the engine at high pressure. Mechanical pumps are typically found in cars that use carburetors, while electronic pumps are typically used with fuel injection systems.

Because mechanical pumps are controlled directly by the movement of the motor and have few moving parts, they are generally reliable and relatively easy to diagnose and fix. Most problems with mechanical pumps occur when the diaphragm is damaged.

Electronic pumps are connected to electronic control systems and contain several moving parts. Because of this increased complexity, these types of pumps are more prone to failure. Any of the parts can malfunction and cause problems with the fuel pump.

The principle of operation of the fuel pump

Schematic diagram of a fuel pump

The main function of a fuel pump is to transfer fuel from the tank to the engine. In injection engines, the fuel pump is connected to the fuel rail, and in carburetor engines - to the carburetor. In this case, it is necessary not only to pump fuel, but also to provide a certain pressure. Too high pressure leads to increased richness of the mixture and high fuel consumption. Too low pressure leads to a lean mixture and a drop in power. Both the first and second cases negatively affect the engine life. That is, the fact that the gas pump pumps fuel does not indicate its full serviceability.

Repair

If the mechanical part of the device fails, there are two options to resolve this issue. In the first case, you can purchase a new repair kit.

It usually includes all the necessary components of the device that can become unusable during operation.

When repairing a device, old components are replaced with new ones.
Usually the diaphragm with valves and the pusher with a spring are replaced.
It makes no sense to change the remaining parts of the device since it will end up costing more in terms of the cost of purchasing spare parts.

In the second case (usually when the device’s case is deformed or damaged), it is advisable to completely replace it.

Gasoline supply problems - common symptoms

Malfunctions of the fuel supply system are conventionally divided into 2 categories:

The combustible mixture is not supplied to the cylinders at all.
Gasoline is supplied intermittently or under insufficient pressure.

In the first case, the engine does not start and does not engage the starter during rotation, that is, it does not show signs of life. In such a situation, it is always easier to determine the cause of the breakdown.

When insufficient fuel enters the cylinders, the following symptoms appear:

starting the power unit “from cold” is very difficult, the engine seizes and “sneezes”, it starts in 3–10 attempts;
idling is unstable, the engine “troubles”;
dynamic acceleration becomes impossible - a sharp opening of the throttle causes a long dip and deceleration;
when the driver releases the accelerator pedal, the engine often stalls;
The car has difficulty climbing hills and accelerates slowly when fully loaded.

The cause of the above phenomena may be a malfunction of the fuel pump or other elements of the system, and the primary symptoms are almost the same. To carry out an accurate diagnosis, you need to understand how the car's power system works.

What pressure should a mechanical fuel pump produce?

The capacity of the mechanical part is about 80 liters per hour, so if the gas pump pumps fuel, there is no need to check the pressure level. The carburetor power system of the car will work correctly even if the fuel is supplied by gravity. Taking into account the undemanding pressure in such a device, the development engineers set the gasoline injection limit to 0.3 atmospheres.

If the fuel pump does not pump, then this part must be urgently repaired or replaced. Operating a car with a faulty gasoline pump can be dangerous: the car can catch fire or stall at the most inopportune moment. Even if no tragic accidents occur, constant jerking of the car while driving will cause accelerated wear of engine and transmission parts.

How to check the operation of the fuel pump?

First, you should check the fuse. To do this, check the instructions for its location. Next, you should check the voltage at the pump. Before doing this, be sure to check if everything is in order with the battery. The voltage at the fuel pump terminal must be checked using a multimeter or tester. The instruction manual always indicates the required voltage.

Using a tester, check the voltage supply to the fuse. Often this is where the electrical circuit breaks.

If the search does not yield results, then the voltage should be checked on the contacts themselves. All contacts must be in place and connected to ground. A broken contact or its oxidation leads to failure of the fuel pump system. If no broken contacts are detected, but the voltage drops by more than 1 volt, then the problem is in the wiring or oxidation of the contacts. There should be no short circuit in the wiring.

If, after checking the voltage, contacts and fuse, you do not find any problems, then the problem lies in the fuel pump itself. In this case, the fuel pump will most likely require replacement. In practice, it most often turns out that replacement is a last resort. First, you should try to restore and test the fuel pump again.

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Before you check the fuel pump, you need to remember that, as mentioned above, pressure is the most important characteristic of the fuel pump, so it is worth measuring its level.

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:

Place the car on a level surface that is prevented from rolling, turn off the ignition and open the hood.
Check that the injection nozzles have access to the fuel rail.
Find the fuel pressure plug and remove it. Then you should unscrew the nipple using the spool.
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).
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.

Fuel rail pressure measurement results

The results may vary slightly for different car models, but in general they should be as follows:

when the ignition is turned on, the pressure must be at least 3 atmospheres,
at idle engine speed - at least 2.5 atmospheres,
when the pressure regulator tube is reset - at least 3.3 atmospheres,
when squeezing the drain tube - at least 7 atmospheres.

Fuel rail pressure fluctuates slightly during preparation. When you press the pedal, it suddenly takes on a value of 3 atmospheres; when you release the pedal, it drops to 2.5 atmospheres. When fuel enters the fuel system, turn off the ignition and begin observing the pressure gauge. The pressure in this case should drop to 0.7 bar and remain unchanged.

If the pressure drops to zero, there may be a problem with the fuel pressure regulator. In this case, the regulator must be replaced immediately. The cause could also be the fuel pump check valve.

It is necessary to observe the behavior of the pressure gauge even at 3,000 engine speeds. A drop in pressure will indicate a faulty fuel pump. Sometimes the fuel pump cannot reach the required pressure for a long time. In this case, the problem lies in a clogged fuel filter, which needs to be replaced, or in a dirty fuel pump mesh (read more about where the fuel filter is located).

If the above methods do not reveal a malfunction of the fuel pump, you will have to diagnose other units (DPZD, IAC, mass air flow sensor, compression in the engine and some other indicators and parts).

What to do if it starts buzzing, humming and stops pumping

This is another serious problem. Electricity is supplied to the pump, but the required pressure is not created in the fuel line. The pressure at which the device can operate must be above three bar. The exact numbers depend on the make of the car.

The pressure in the fuel rail increases. It must be 300 kPa or more. A pressure gauge is used to measure it. In this case, it is necessary to take into account the standard indicators for this machine. Take, for example, the VAZ injector. When you turn the ignition key, a pressure of 3 atmospheres is created, at a minimum - 2.5 atmospheres, when you press the gas - 2.5-3 atmospheres. In this way, you can reliably determine problems in the operation of the fuel pressure regulator in the rail, problems in the operation of the fuel pump associated with its failure or the expiration of its useful life. This will also help you know if the filters are dirty.

The easiest way to get a pressure gauge is to measure the pressure in the fuel system. So you don't have to pay for this service at the gas station.

The pump pressure may be abnormal. Because of this, the engine simply does not start or starts with great difficulty, contracts, runs intermittently and fails. If the reason is a malfunction of the pump itself, and not the filter, then most likely it is necessary to clean the mesh designed for rough cleaning. Then you won't have to change it.

Problems also arise due to failure of the relay, electric motor or fuel pump fuse, or a malfunction in its ground.

Other reasons why the device does not hold pressure:

skip the nozzles.
problems with the check valve;
violation of the pressure regulator;
hole in the fuel system;

Using a pressure gauge you need to connect to the fuel system. Then you need to start the car and set the pressure level. If the pressure is 2.9 kg/cm², the engine must be stopped and then started again.

Close the line to the valve on the pressure gauge and stop the engine immediately. If the pressure is normal, the fuel pump and valve are working properly. If the pressure drops after the valve opens, the fuel injectors or fuel pressure regulator are not working properly.

The valve can be connected to a pressure regulator. You need to start the car and remove the hose from the intake manifold. If the pressure immediately begins to rise, the valve must be returned to its place. The pressure should now immediately begin to drop. And repeat this several times. Turn off the engine. If the pressure holds, then everything is fine.

The vacuum pump may not work properly. This can happen for several reasons:

Features of the injection power system

The tasks of fuel pumps in carburetor and injection engines are somewhat different. If for a carburetor engine it is important to simply supply gasoline to the carburetor, then for an injection system this is not enough. The fuel pump must not only pump fuel from the tank to the ramp, but also create a certain pressure, without which the engine simply will not start.

Access to the fuel pump in injection cars is also complicated by the fact that in cars of recent years of production it is mounted together with a fuel receiver and a coarse filter directly in the gas tank. This complicates the diagnosis, repair and maintenance of the entire fuel module, but simplifies the design of the pump, since the gasoline itself lubricates and cools it. But this is precisely what often leads to unit breakdowns.

Checking the serviceability of the pump on the injector

If you hear a slight noise when turning the ignition key, then this is how the fuel pump functions. By pushing up the fuel, it creates pressure in the structure. If, when trying to start, there are no similar symptoms of the fuel pump, then we can assume a breakdown of the electrics, the fuel pump or its separate elements.

Purpose and principle of operation of the fuel pump

The fuel pump is designed to pump fuel from one point to another. In a car, the role of the first point is played by a fuel reservoir - the tank, and the second - by the engine, where the pumping takes place. This process occurs at a certain pressure, which is maintained by the pump reducer, which is a very important point.

Fuel pump diagram

Fuel pumps are divided into 2 types according to the type of drive: electric and mechanical. Inside the first there is an electric motor with a mini-pump, which operates from the mains and uninterruptedly pumps fuel into the engine. The second type is becoming increasingly rare, as it is installed on carburetor cars, and operates due to the reciprocating movement of the lever.

Fuel pump diagram

Check fuel pressure regulator

The fuel pressure regulator is mounted on the rack or in the fuel pump module. Checking for a faulty valve is done using the same pressure gauge for diagnosing fuel pressure. Procedure:

Screw the device into the gap in the fuel supply line;
Turn on the ignition;
If the fuel pump does not turn on, turn on the starter;
Wait until the fuel pump turns off. The pressure should not decrease by more than 0.5 atm. If it drops to zero, the check valve is faulty and is draining fuel into the tank;
When the pressure exceeds the permissible level, we can talk about the fuel pressure regulator being jammed.

Thus, a malfunction of the check valve on the injector can be determined using a conventional pressure gauge. Just follow the instructions above.

Signs of a malfunctioning RTD (fuel pressure regulator):

Bad start. If the valve is leaking, the pressure in the rail has time to decrease before the engine starts;
If the RTD is clogged, pipes can rupture as the system pressure rises to the maximum output from the gas pump.

These symptoms are typical for domestic cars. When switching the RTD you may pinch the return pipe and the regulator will reset. As a rule, this method helps. None of the sensors in the electronic control system will detect this malfunction.

Cause of malfunction

A common malfunction of a mechanical gasoline pump is mechanical wear of its rod. When the fuel pump rod becomes shorter than necessary, it stops supplying fuel to the carburetor in the required quantity.

Worn suction valve or brass valve and sealing gasket on a mechanical fuel pump can be another cause of fuel pump malfunction.

The main sudden malfunction of the fuel pump on a car with an injection engine is low-quality fuel. Of course, the question of cleaning lies behind the fuel filter, but the fact is that the fuel injection system of a modern car is made in such a way that the finest filter element is installed after the fuel pump, and in front of it there is only a coarse filter mesh (by the way, it has to be changed or clean more often to avoid fuel pump malfunction). The strainer cannot ensure proper cleaning of the fuel available at our gas stations, and the accumulated dirt on the filter forces the pump to strain to overcome resistance. Which subsequently leads to a reduction in the service life of the part.

For car owners abroad, the fuel pump is more likely to fail due to wear on the manifold assembly in the electric motor than due to a dirty filter. But for our drivers, a typical cause of failure is severe wear and tear of the working surfaces of the fuel pump. This problem may be indicated by loud noise during operation, which will be accompanied by a drop in pressure in the fuel system and increased fuel consumption.

Also, if the issue concerns a malfunction of the electric fuel pump, worn wiring or oxidized terminals can play an insidious role. And when checking the pump shows that everything should work without failures, the electrical wiring will be baffled over and over again.

From all of the above, you can draw several conclusions for yourself:

Firstly, you need to refuel with high-quality fuel, and also periodically clean the fuel tank.
Secondly, replace the fuel filter on time.
Thirdly, listen to the pump.

Here are the basic recommendations to extend the service life and protect yourself from fuel pump malfunctions.

Measure the fuel pressure in the rail

As mentioned above, to measure the pressure of the fuel pump in the rack, the pressure gauge must be sequentially screwed into the fuel supply. The measurement is carried out in different ways, depending on the symptoms of the malfunction:

How to check the fuel pump in the wall. This procedure is necessary to avoid clogging of the filter and fuel pressure regulator lines. The pressure value at the nozzle in the wall should be 6 atm.
The craving is gone. First you need to measure the fuel pressure at the ignition switch, if it gives normal readings, measure it at idle. The pump should produce 2.5 - 4.2 atm, depending on the type of engine. 2.5 – RTD on the ramp, 4.2 – RTD in the tank.
There are cases when the owner complains of a short-term loss of traction or due to heat. In this case, you need to check on the go. We attach the pressure gauge and check the tightness of the contact with the fitting so that there are no gasoline leaks. We fix the device on the windshield, under the wiper and off we go. If the fuel pressure drops while driving, it is necessary to replace the fuel pump, filter, and purge lines.
The car won't start. We take measurements with the ignition on. Through the diagnostic scanner, you can turn on the fuel pump through the actuators. Working pressure from 3 to 4 atm.

With these simple steps you can measure gas pressure on any car. The main thing is to follow safety precautions when working with flammable liquids.

When should you check your fuel pump?

It is necessary to check all potentially faulty components one by one, and the fuel pump first.

Problems when starting and running the engine are not always associated with the fuel pump. Sometimes the signs of a fuel pump breakdown are the same as those of a faulty fuel pressure regulator , injectors or jets, spark plugs and high-voltage wiring. Even experienced specialists who know by heart all the signs of a “dying” pump cannot unambiguously determine the type and cause of the breakdown the first time, and it is necessary to check all potentially faulty components one by one. In this case, the fuel pump is usually checked first. In this case, there are two types of malfunction - the fuel pump does not work at all or does not produce the required pressure. In the first case, the malfunction can be recognized by ear, since it should start when the ignition is turned on. In the second case, you need to know how to check the pressure of the fuel pump. Here you need to use a special pressure gauge. We list the main symptoms of a fuel pump malfunction:

the engine does not start;
the engine is unstable;
the engine lacks traction during sharp acceleration;
The engine lacks traction at low speeds.

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Diagnostics of the fuel pump of a carburetor car

You can check the performance of the fuel pump of a carburetor car without using any instruments. Diagnostics are performed in the following sequence:

The fuel hoses are disconnected from the fuel pump.
The fastening bolts are unscrewed.
The fuel pump is removed from the cylinder head.
Use the thumb of your right hand to close the inlet fitting of the fuel pump.
Using the thumb of your left hand, apply several pressures on the pump pusher.
The appearance of a vacuum at the incoming fitting will indicate the serviceability of the membrane and inlet valve.

In a similar way, you can check the serviceability of the outlet valve by holding the outlet fitting with your finger and making several intense movements with the pump pusher. If the device is working properly, positive pressure will form at its outlet.

Symptoms of a faulty fuel pump on carburetor engines are almost the same as when using an electric device. The difference can only be observed in the absence of characteristic noise from the operation of a twelve-volt motor.

Design and operation of fuel supply

The system that provides the engine with the required amount of gasoline operates according to the following algorithm:

After turning on the ignition, the electric fuel pump starts, raising the pressure in the line after itself to a certain level. The electrical power supply circuit of the unit is protected by a fuse.
The fuel pressure regulator (common abbreviation - RDT) is located on the line after the pump and limits the upper pressure threshold, dumping excess fuel back into the tank through a separate pipeline.
When the crankshaft is rotated by the starter and the engine continues to operate, fuel enters the fuel rail, mixes with air and is directed to the injectors built into each cylinder. The amount of mixture supplied to the combustion chambers is controlled by an electronic unit.
On the way to the fuel rail, gasoline goes through 2 stages of filtration. The first is a mesh installed in the tank on the suction pipe of the pump, the second is a fine filter on the gas supply line.

Reference. In various car models, 2 schemes are used for installing the RTD and laying the return pipeline - in the engine compartment or directly in the gas tank. In the first case, the standard fuel pressure in the system is 2.7...3.0 Bar, in the second - 3.8...4 Bar.

A common mistake made by ignorant car enthusiasts: if the combustible mixture does not enter the cylinders, then the fuel pump is definitely not working. Knowing the design of the fuel supply, we can assume other problems:

the protective fuse in the electrical circuit has blown, the pump is in good working order, but does not receive power;
the primary or secondary filter is clogged (sometimes both at once), fuel flows in small quantities or does not flow at all;
the pressure regulator has become unusable, dumping the lion's share of the fuel back into the tank, the engine gets nothing;
One or more injectors have failed.

To accurately determine the source of the problem, you need to check the operation of the electric fuel pump and other elements. It is not necessary to go to a service station - diagnostic work can be carried out in your own garage.

The gasoline pump does not pump: reasons

If the gasoline pressure becomes lower than possible and the pump stops functioning, then it is necessary to understand why the pump does not pump fuel. If there is no hum in the fuel pump, i.e. it does not turn on when the ignition is turned on:

You need to check the 12 Volt power supply, as well as the ground on the pump chip. If the relay does not work, then you need to install an electronic control unit “brains”. If there is no voltage, then the cause should be found and eliminated in the electrical circuit of the machine.
Then, if there is voltage and ground, you need to check whether the wires in the fuel pump are damaged. To do this you need to remove it from the tank. On VAZ modules, the chip in the pump housing often burns out. Then you will need to replace the chip and the upper connector on the module body.
If everything is fine here, but the motor does not work, then connect 12 volts from the battery to the module and also check the hum of the pump. If the pump does not function, this means that it is broken and the pump motor needs to be replaced.

And if the fuel pump is functioning, but does not pump fuel, then you need to check:

Fuel pressure in the rail.
Clogging of pipelines, fine and coarse filters.
Fuel pressure stabilizer for functionality. It is located on the ramp or in the fuel pump module (in the tank).
A frequent cause of breakdown is water in the tank, which turns into ice in winter, so the pump functions, but does not provide the necessary pressure.

Causes of fuel pump failure

If the cause of the malfunction lies in the fuel pump, this does not always mean that it is faulty. The malfunction may be in one of its units and parts. For example, a fuse may blow. It is located in the fuse box, and its location may be different for each car. You can find out its location from the operating instructions. Most often it is located under the hood or to the left of the steering wheel on the driver's side.

The fuel pump, like any other device, wears out over time and fails. If there is a suspicion that the fuel pump is faulty, it should be diagnosed immediately.

Replace with a new one or not

If the malfunction concerns a mechanical part, the driver has two ways to solve the problem. The first thing is to buy a repair kit. Includes all necessary parts that may break in the pump. The second is to replace the entire element with a new one. This is a more reliable and reliable method. But it is worth considering that submersible pumps are very expensive. Among the manufacturers on the market there are both originals and analogues.

Diagnostics with pressure check

A more accurate diagnosis can be made by again measuring the pressure in the system. Each of the indicators below, or more precisely, a deviation from the norm, can signal certain problems with the pump:

the idle pressure must be at least 0.23-0.25 kPa;
at the moment the engine starts, the pump should create a pressure of about 0.3 kPa;
in transient modes - 0.28-0.3 kPa.

In the case when, when the ignition is turned on, fuel does not enter the system and the pressure gauge is silent, most likely the problem is in the electronics - a relay or fuse. If the pump does not develop the required pressure during transient conditions, the coarse filter mesh is clogged. If the fuel return hose is pinched and the pressure is below 0.4 kPa, the pump is worn out.

Fuel pressure measuring device

As mentioned above, the operation of the fuel pump is controlled by a special device - a pressure gauge. The most common MP is 100 produced by NTS LLC. We have been using it in our service since 2008, the accuracy of the readings has remained at the factory level. Includes adapters and safety valve.

Pressure gauge MP – 100

It allows you to measure fuel pressure both in the rail with the fitting and at any point in the fuel line. The kit with pressure gauge includes adapters:

The adapter extension UP-2 allows you to take measurements on rear-wheel drive classics.

Adapter TPB-2 for quick connectors.

It allows you to easily measure pressure on most modern cars.

There are many similar fuel pressure meters. Differences in price, size, dial. Structurally, all counters are similar. You can make a pressure gauge with your own hands, but the price is not worth it. It is much easier and more effective to contact diagnostics or any service. They will draw a conclusion and fix the problem.

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:

All scheduled vehicle repairs must be accompanied by the replacement of all fuel filters.
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).
Eliminate the possibility of water getting into the fuel tank.
Protect the fuel pump housing from mechanical stress that causes dents and cracks that contribute to the development of corrosion processes.

What is a pump for?

The fuel pump is a critical component that pumps fuel towards the engine carburetor. At the same time, it is important that fuel is supplied to it under some pressure, which guarantees uninterrupted operation of the engine.

Additional information: On cars with direct injection and a high-pressure pump (HP pump), this device is used as a booster unit.

Based on the type of drive and design features, two types of pumps are distinguished: mechanical and electric.

In mechanical samples, the diaphragm of the unit, when pumping, vibrates with a cam mechanism, creating a vacuum. Due to this, fuel under pressure enters the engine. Their electric or injection analogues contain an electric motor with a miniature pump powered by the on-board network. In these systems, all information about the state of the fuel line is collected and transmitted to the on-board computer. And the latter, based on it, ensures optimal engine operating conditions. Below we will mainly consider just such systems (they are called injectors).

Similar symptoms not related to the fuel pump

The symptoms that appear due to a lack of fuel in the supply line are quite typical and are very similar to problems with other systems. How to eliminate possible problems using the elimination method:

Unscrew and inspect the spark plug skirts. When there is not enough fuel, the electrodes remain clean or become covered with a white coating. This is further evidence of a malfunction in the power system.
Replace spark plugs. If they wear out, they create a similar effect - failures, difficult starting, and a drop in engine power.
Check the functionality of the throttle position sensor (TPS) and idle air control.
Measure the compression in all engine cylinders. Due to excessive wear, the naturally aspirated engine is unable to create the required pressure and vacuum; the mixture burns poorly, which is why identical symptoms occur.

When troubleshooting, take into account one important factor - the service life of the fuel pump, which is at least 100 thousand kilometers. The longer the operating period of the unit, the lower the fuel pressure it creates at the outlet. The reason is wear of the membrane and other internal parts. If the pump has served 150 thousand km or more, you should think about purchasing and installing a new spare part.

Injection engine: briefly about the fuel pump

The era of carburetor internal combustion engines is over. At least in relation to cars. They were replaced by more advanced and modern injection power units. This fundamentally changed the car's power system, but did not eliminate the need to deliver fuel from the tank to the engine. This function is still assigned to the pumps. Unlike a similar unit in a carburetor engine, the fuel pump of an injection engine has a different design, which means a different principle of operation and malfunctions unique to it. Let's talk about this.

Injection engine: pump design

There is probably no car enthusiast who does not know the structure of a classic fuel pump. And of course everyone remembers, and some probably still encounter it, that it is installed directly on the engine. This is very convenient, you don’t need to think about an additional drive, and you don’t need an autonomous lubrication system. But there is one significant drawback. The pressure that a mechanical fuel pump can create is not enough for the correct operation of an injection engine.

In addition, in an injection engine, the fuel pump must operate in strict accordance with the commands received from the electronic control unit. It is the ECU that selects the operating mode of the pump, based on the analysis of many parameters. It is almost impossible to implement such an algorithm on gears. That is why, unlike a carburetor engine, the fuel injection pump is not mechanical, but electric. In addition, it is installed in the fuel tank. This allowed us to solve a number of problems:

Significantly increase productivity due to the fact that the pump has become submersible;
Solve the cooling problem. Gasoline has a very low resistivity, that is, it is practically an insulator. The designers took advantage of this. The windings of the electric motor are in gasoline and are cooled by it.
Reduce noise. This became possible again due to the fact that the pump is completely immersed in fuel.

Now the very principle of operation of the injection fuel pump. In general, electric pumps can be structurally:

The latter are the most common, so they are the ones we should talk about in more detail.

The key element of a centrifugal pump is the impeller mounted on the electric motor shaft. It is located in the pump housing, which has an inlet and outlet. When the impeller rotates, a centrifugal force arises, which presses the gasoline against the housing and pushes it out into the outlet. At the same time, a vacuum arises in the center of the impeller, which is filled through the inlet with a new portion of gasoline. Thus, there is a continuous supply of fuel to the injectors of the injection engine. Thanks to the special design of the impeller, sufficient pressure is generated in the fuel line for their normal operation. It is maintained even when the pump is not running, thanks to the check valve. That is why experts recommend that when doing any work on the fuel line, the first step is to relieve the pressure. Anyone who has changed the fuel filter knows this. Here, in brief, is everything that concerns the mechanical part of the fuel pump of an injection engine.

Now a little about its electrical component. The electric motor of the pump is powered by a voltage of 12 V, and it is controlled, as already mentioned, from the motor controller. It would seem quite logical that it is from the ECU that power is supplied to the electric motor terminals. But no. Its power, at least 60W, does not allow this to be done directly. Therefore, a relay is introduced into the fuel pump power circuit. It’s called the fuel pump relay (FPR). This is where power is supplied from the controller. When activated, the relay closes the fuel pump power circuit with its contacts. Looking ahead, we can say that the relay is one of the main reasons for the unstable operation of the fuel pump, and ultimately the injection engine itself. But this is a topic for a separate conversation, but for now let’s briefly summarize. So:

The fuel pump of an injection engine is electric, submersible and is most often installed in the fuel tank;
It has a centrifugal design and provides pressure through the rotation of the impeller;
The electric motor of the fuel pump is cooled directly by the fuel;
The fuel pump is powered by a constant voltage of 12 V;
The engine controller controls the fuel pump through the RBN.

Repair and replacement of the fuel pump VAZ 2107

First, let's figure out what the power supply system of the VAZ 2107 injection engine consists of.

Diagnosis and Troubleshooting

It is relatively simple to verify that the electrical network is faulty - this can be done without removing the fuel pump. When the sound of its operation is not heard when the ignition is turned on, you must immediately check the fuse responsible for this circuit. It is installed in a block mounted at the bottom in front of the front passenger seat. You need to remove the block cover, find the fuse marked F3, rated for 15 A, and replace it. This kind of work can be done on the road.

If the operation of the fuel pump has not resumed, you should switch your attention to relay K2, located in the same block. It closes the power circuit of the pumping device based on a signal from the controller. You can also check the serviceability of the relay in road conditions, for which you will need a piece of copper wire. Diagnostics are carried out in the following order:

Remove relay K2 from the connector.
Turn on the ignition.
Using a wire, connect the contacts marked “30” and “87”; the numbers are marked on the relay. Another option is to apply power to pin “11” located in the diagnostic connector. The +12 V voltage can be taken nearby, from the cigarette lighter.
If you hear the pump humming, then you need to change relay K2.

If after the above manipulations the unit is still “silent”, it is necessary to check the integrity of the wiring and the reliability of the contact at the place of its connection. This will require a device, so it will not be possible to carry out such work in the middle of a field. Unless you can check the serviceability of the fuel pump itself by disconnecting the connectors from it and supplying 12 V directly from any convenient source. If the pump still does not hum, it should be replaced.

Be careful when connecting wires directly and make sure that there are no drops of gasoline nearby, as a spark may cause it to ignite.

It will not be possible to diagnose insufficient fuel supply to the injectors under road conditions, unless you carry a pressure gauge with a corresponding hose for connection to the fuel rail. The amount of gasoline supplied is characterized by the pressure in the network, to measure which you will need a pressure gauge. The check is performed as follows:

Twist off the plastic cap covering the diagnostic fitting. It is located at the end of the fuel rail and is a regular spool.
Press the spool rod to release the pressure in the line. In case of gasoline leakage, place a small container under the spool. Perhaps the malfunction will make itself felt already at this stage if there is no pressure in the network and no fuel flows from the fitting.
Unscrew the spool and put the hose from the pressure gauge onto the fitting. With the ignition off, apply 12 V directly to the pump. To clearly record the readings, it must work for at least 10 seconds.

If the pressure is below 3.6 bar, you must first change the coarse filter. If this does not help, then you will have to check the RTD and the tightness of the injectors. This is the only way to accurately determine the source of the problem.