No pressure in the fuel rail VAZ 2109 injector 8 valves

Fuel pressure diagnostics

© Alexey Pakhomov, aka Is_ 18, Izhevsk
Fuel pressure is one of the most important engine parameters from a diagnostic point of view. The composition of the mixture, and therefore the behavior of the car in various modes, depends on it. Let's try to integrate diagnostic methods based on fuel pressure into a system. Naturally, you will need a fuel pressure gauge to work. It is best to purchase a device with a large, easy-to-read scale, the measurement limit is 5 - 6 kgf/cm 2. For example, like the one in the photo. The use of pressure gauges with a limit of up to 10 - 12 kgf/cm 2, used in the diagnosis of foreign cars, is hardly advisable due to the relative inaccuracy in the range of 2 - 3 kgf/cm 2. So, we connect the pressure gauge and diagnostic scanner.

1 . First of all, we evaluate the operation of the pressure regulator. To do this, turn on the pump with the engine not running. The pressure gauge should show 3. 0 +/- 0 . 2 kgf/cm2. If the pressure is below 2. 8 kgf/cm 2, it is better to change the RTD, because in power modes the machine will be dull. We pronounce the final verdict on RDT only after the next point.

2. Next, check the zero supply pressure. The name of the parameter speaks for itself - this is the pressure developed by the pump, as they say, “to the plug”, that is, fuel is not supplied. Indirectly, this parameter indicates the residual life of the pump; as it wears out, it gradually decreases.

So, take the pliers and pinch the “return”. This needs to be done quite sharply. The pressure gauge needle should literally shoot towards the limit value. If it rises slowly, then the fuel filter or fuel inlet mesh may be clogged. The limit value itself speaks volumes. If the pump is new, it will reach 5 - 6 kgf/cm2, and on pumps made in the Czech Republic - up to 7 kgf/cm2. In any case, if the pressure exceeds 5 kgf/cm2, then the pump has a sufficient resource. The manuals give different values ​​of zero supply pressure at which the pump supposedly requires replacement. But in practice, if the pump “on the plug” presses at least 4 kgf/cm 2, it can still go on and on. In reality, customers complain about the dullness of the car when this parameter no longer reaches three “points”.

3. Turn off the pump. The pressure should drop to approximately 0. 7 kgf/cm 2 and remain at this level. If it immediately drops to zero, then either the pump check valve or the RTD is faulty. This defect, of course, is not fatal, and is often eliminated by briefly squeezing the return line. If it turns out that the RTD is at fault, it can be replaced, but changing the fuel pump due to the check valve does not seem advisable, at least according to customers.

4 . We start the engine. We carefully monitor the pressure gauge needle. This is where the larger scale comes in handy. The needle may tremble slightly, this is a consequence of large pulsations of absolute pressure (pressure in the intake receiver). These pulsations are a topic for another discussion; let’s forget about them for now. But if the needle does not tremble, but “walks”, and within a fairly wide range (up to 0.3 kgf/cm2), then the gas inlet mesh is probably clogged. For example, like in the photo. (note from Sim - this is not the most extreme option - see more “cool” cases HERE)

5 . With the engine running, the pressure will be about 2. 3 kgf/cm2. If you remove the vacuum hose from the RTD, it will rise sharply to 3 kgf/cm2 (or to the value obtained in step 1). Put the hose back on. Smoothly raise the speed to about 3000. If the pressure gradually drops, then this is another sign of a “dead” pump.

6. You can also check the performance by unscrewing the fuel supply line and applying power to the fuel pump. About 1 should run up in a minute. 5 liters. To be honest, in all my practice I have never done this; I somehow made do with the pressure gauge readings.

7. The most extreme option is a pressure of about 1 “point” and an uneven sound of the pump. The reason is there is no gasoline in the tank. Not funny. I regularly send my cars to refuel once a month.

That's all simple science. If you had to disassemble the gas tank, it makes sense to look into it with a flashlight. At the bottom you will find water, rags of dirt, sand and other unnecessary substances. They need to be removed with a pear. Or better yet, if you have one, use a vacuum unit for changing the oil. Since we remembered the tank, one more piece of advice. To prevent the gas tank from turning into a cake in winter, drill its cap from the back side. The method is stupid and not recognized by all experts, but it is radically effective. Good luck!

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Take a pressure gauge (in the photo a device for measuring tire pressure). We wind the foam (plumbing flax) under the pipe and put on an oxygen hose with an internal diameter of 9 mm. Secure with clamps. Place a rag on the generator (so as not to start a fire under the hood). Unscrew the plastic cap on the fuel rail.

Under the cap there is a hole with a nipple. Unscrew it from the wheel cap. Due to the residual pressure in the rail after removing the nipple, gasoline will splash out.

If desired, you can relieve the pressure in the vehicle's fuel system . To do this, you need to remove the fuel pump fuse (under the right trim of the center console near the ECU, where there are 3 relays and 3 fuses. Usually the fuel pump fuse is on the far left) and wait until the car is running and does not stall.

We put the second end of the hose on the ramp hole and secure it with a clamp. We remove the rag from the generator and start the engine. Don’t forget to cover the generator with a rag again before removing the hose from the ramp. That's it, now you know how to check the pressure in the fuel system in the field .

By the way, instead of clamps, you can use the bushing of the classic adjusting bolt (item 27 in the figure). It screws perfectly onto the “tens” ramp fitting. To seal, we put a suitable rubber ring on the fitting. On the other side of the bushing we solder a fitting onto which we put a hose with a pressure gauge.

1 – fitting for checking the pressure in the power system; 2 – fuel rail; 3 – nozzles; 4 – fuel line; 5 – fuel tank; 6 – fuel pump module (in the fuel tank); 7 – fuel filter; 8 – tee.

Video showing the process of checking the pressure in the fuel system of a car:

Car diagnostics using fuel pressure

Problems in the operation of the car's fuel system are expressed by failures at high speeds, jerking of the car, or the car does not move when you need to accelerate sharply, and sometimes it simply stalls. Now knowing how to check the pressure in the fuel system of a car, we can diagnose the car ourselves. We can determine which component of the fuel system has failed (fuel pump, fuel pressure regulator (FPR), injectors, filters, etc.), but first we need to understand how the fuel system works: The fuel pump continuously pumps fuel while the engine is running. Excess gasoline is stupidly dumped through the RTD into the return line. The pressure in the ramp changes (increases) not so much with the speed, but at the moment of accelerating (this is clearly visible in the video), because at this moment, the vacuum (vacuum) in the receiver drops and the RTD adds pressure to the ramp. If you turn off the engine, the pressure in the ramp will slowly begin to decrease exponentially. The rate of decline (from several minutes to several hours) depends on the quality of the check valve, which is located on the back of the fuel pump motor.

When diagnosing, pressure measurements in the system are made in different ways:

Checking the fuel pump “for a plug” is quite simple; you need to pinch the return line with pliers (for 2-3 seconds) with the car running and watch the pressure gauge readings.

Another way to check the fuel pump: smoothly raise the engine speed to 3000 rpm. If the pressure gradually drops, then this is a sign of a “dead” pump.

Signs of a fuel system malfunction

Low or excessive pressure in the fuel rail leads to the following consequences:

• unstable engine operation;
• not smooth idle;
• engine tripping;
• increased consumption;
• power drop;
• the engine stalls at idle;
• increased CO content in exhaust gases.

If you encounter one of these problems, and ECU diagnostics do not give any results, then the first thing you need to do is measure the pressure in the fuel system.

The pressure in the fuel rail is measured according to the same principle as in the tires.

Pump operating principle

The VAZ 2109 fuel pump has a fairly simple design; the injector functions only thanks to it. It is based on two elements - an electric motor and a pump with a filter element. Please note that the “diaper” (as people call the filter for its similarity) needs to be changed on time - try not to let it work for more than 20 thousand km. Otherwise, it becomes saturated with metal shavings, dirt and other rubbish, which gets into the line and clogs the injectors.

We take a measurement in the fuel rail.

To work we need a “pressure gauge”. But not every pressure gauge is suitable, it all depends on the pressure limit that it can measure. In our case, we need a pressure gauge with a measurement limit of up to 7 atmospheres. If you have a pressure gauge measuring up to 17 atmospheres, then such a device will show incorrect data, because it has too much error at low pressure.

In addition to the pressure gauge itself, we will need “plumbing flax”. We wind flax under the pressure gauge nozzle and put a hose with an internal diameter of 9 mm on it. Next, we tighten the whole thing with a clamp. Our device is ready for use.

In a store, such a device with a hose and drain will cost you about 1200 rubles. Measuring the fuel system at a service center will cost you about 200-300 rubles.

1. Open the hood, turn off the ignition, find the fuel injector rail.
2. We unscrew the plug of the fitting for fuel pressure, then use a spool to unscrew the nipple that appears, carefully placing a container or rag, because gasoline will spray due to remaining fuel pressure.
3. Place the pressure gauge hose over the fitting and secure it with a clamp.

You need to check the pressure in 4 operating modes:

• measure the pressure when the ignition is turned on;
• measure the pressure at idle;
• measure the pressure with the tube removed from the fuel pressure regulator;
• measure the pressure with the return pipe pinched.

Purpose and principle of operation of the VAZ 2114 fuel rail

Injection car engines on the VAZ 2114 are power units with distributed injection, which occurs through injectors installed on the fuel rail. The ramp itself is a tube, or a hollow bar with ends welded on both sides. It is attached to the intake pipe on the engine intake manifold with two bolts. There is a separate line for draining excess fuel from the RTD into the tank.

If you think this article sucks, please contact Dave directly and let him know what you think. Often the term "fuel pressure" is used with little understanding of what it actually means. This leads to confusion about injector flow and people lose sight of how their injectors actually work. Understanding how fuel pressure works and applies to both return and return flow systems is important if the user wants to properly tune injector characteristics and achieve predictable fueling.

The pressure in the VAZ 2114 fuel rail in front of the injectors is maintained by a fuel pressure regulator. The fuel pressure must always be higher than the intake manifold pressure, because otherwise the fuel from the injectors cannot be injected to create the mixture. Moreover, the pressure in the intake manifold changes depending on the speed and the driver’s work with the gas pedal. And in TR this figure should be constant - no less than 2.9 kg/sq.cm. and no more than 3.3 kg/sq.cm.

Work order

Knowing what to expect also allows the user to diagnose problems with their fuel system and ultimately get the vehicle running as intended.
There are two pressures that people need to consider: rail pressure and effective pressure. For the purposes of the rest of this article, this will simply be referred to as effective pressure. Rail pressure goes without saying; this is the pressure inside the rail. When you push the fuel pressure sensor at the end of the rail, it reads the pressure inside the rail. The RTD on the engine is located above the ramp, and it is structurally designed in such a way that when the power plant stops and the ignition is turned off, it closes completely and cuts off the gasoline supply. As a result, a constantly high pressure is maintained in the TP tube for a long time. Therefore, when starting, gasoline is supplied to the injectors under pressure and starting occurs without delay.

While this number is important, it is only half the story. Effective pressure is what the injector flow rate is ultimately based on. When the engine is idling, there is a vacuum in the intake manifold. This vacuum forces fuel out of the injectors and increases the effective pressure on the injector to a pressure greater than the rail pressure. When a supercharged or turbocharged engine is in boost, the pressure inside the manifold device attempts to return fuel to the injector, resisting flow and reducing the effective fuel pressure below the rail pressure.

Attention! If the fuel pressure regulator is faulty, the pressure is released during prolonged parking and is insufficient for normal starting. The RDM is beyond repair and must be replaced.

The driver can become aware of the occurrence of malfunctions in the vehicle engine when the following signs appear:

On-board diagnostics to identify faults

There are two typical types of fuel system installations: return and return style.
The non-return system does what the name implies and does not return fuel to the tank. Return systems return excess fuel back to the tank through the regulator. With a reverse system, the base pressure is set with the engine off but the pump running. The regulator will continuously evacuate pressure within the rail to maintain the same effective pressure under all operating conditions. This helps prevent loss of effective pressure during wide open throttle and also helps prevent the injectors from firing extremely low pulse widths to deliver fuel at idle. The downfall of return systems is the fact that they circulate fuel through a very hot engine compartment, eventually transferring that heat back into your fuel tank.

• The power plant stalls at idle
• At idle the engine speed starts to fluctuate
• During the movement, unstable operation of the internal combustion engine is felt, which is expressed in floating speeds
• the engine starts to stall
• increased gasoline consumption is noticed
• When the ECU is working properly, engine power drops
• increased carbon dioxide content in the exhaust

One of the first actions that the driver must do is measure the pressure in the VAZ 2114 ramp.

A return style system, which is not variable, will maintain a certain pressure inside the rail regardless of what is happening in the manifold. No matter what the operating condition, the rail pressure will always be 58 psi. At 20 inHg idle, this means the effective pressure will rise to 68 psi because manifold vacuum adds 10 psi. Inch to rails 58 psi. This requires the injectors to pulse shorter so as not to overload the engine and cause more conditions.

What pressure should the fuel system have?

A normal fuel system should have the following indicators:

• at idle 2.5 atm;
• ignition – not lower than 3 atm;
• when removing the vacuum tube 3.3 atm;
• when squeezing the drain tube - 7 atm;
• when accelerating, it jumps to 3, then drops to 2.5 atm.

Important! Make sure that the fuel line does not contain any holes: fuel is not leaking anywhere, otherwise the pressure measurements will be false.

1. After we have pumped fuel into the system, turn off the ignition and look at the behavior of the pressure gauge. The pressure in the rail should drop to 0.7 bar and remain at this level, but if the pressure immediately drops to 0, then the problem is in the fuel pressure regulator (how to remove and replace the RTD), or the check valve of the fuel pump motor.
2. We raise the engine speed to 3000 and look at the pressure gauge readings; if in this mode, the pressure gauge needle drops, the problem is a dying fuel pump.
3. If the fuel pump takes a long time to build up pressure, the fuel filter or strainer in the tank may be clogged.

If, after replacing the fuel cells, your problem remains, then check other systems: IAC, TPS, MAF, compression in the cylinders.

What is a fuel pressure regulator?

The fuel pressure regulator (FPR) is a vacuum valve that transfers excess fuel through a return hose into the fuel tank. The RTD is a housing that contains a valve, a membrane and a spring. There are also three terminals in the housing: two terminals for the passage of fuel through the regulator, the third is connected to the intake manifold. As engine speed increases, the vacuum created in the manifold (at the third terminal) overcomes the force of the spring and moves the membrane, thereby opening the valve slightly. Excess fuel gets access to the second outlet and goes back to the gas tank. An RTD is often also called a check valve.

Signs and symptoms of low pressure in the system

Weak pressure is expressed primarily by the presence of dips. You try to accelerate, press the gas pedal, nothing happens. Stopping the engine and then starting it helps (this way the pump pumps fuel). However, after ten or fifteen kilometers the situation repeats itself.

Some drivers even change the fuel filter or pump strainer in the hope of improving the situation, but this does not help. Replacing the mesh in this case is considered as a more correct option. The fact is that the pressure can drop due to a poorly functioning pump.

If the problem is not in the mesh, then the pump itself is dying. There is another reason - it is the vacuum of the fuel tank. This is how it is checked. You need to stop the car if it starts leaking, sneezing, etc. But don't turn off the engine. Then open the tank flap and loosely close it again. Continue driving, if the dips disappear, it means there is definitely a vacuum in the tank.

The lid may not be closed at all to allow air access. When there is a vacuum it is not enough. If the problem repeats, the failures do not disappear, the fuel pump must be considered the culprit.

A clogged fuel line and a malfunction of the sensor that regulates the fuel pressure immediately before injection can also cause low pressure. To reliably verify why exactly the pressure is jumping, it is necessary to carry out competent measurements. First measure the pressure of the pump, then the lines (before and after the filter), and then directly in the ramp. Such instrumental monitoring will allow us to identify a specific cause.

This sensor is often ignored by motorists, but it is its malfunction that can lead to insufficient pressure. Symptoms of a failed sensor:

• loss of car dynamics;
• Unstable engine speed in idle mode;
• difficulty starting;
• failures;
• increased fuel consumption;
• reduction in power.

Violations with RTD occur quite often, since the design of the sensor is mechanical.

1. The membrane springs weaken. As a result, the valve cannot cope with the air pressure coming from the manifold, which leads to a decrease in pressure and the amount of incoming fuel.
2. The valve jams, the connections lose their tightness. Because of this, the RTD becomes clogged. In general, a stuck valve can lead to an uncontrolled flow of fuel into the manifold. Fuel consumption instantly increases, the engine stops starting normally due to interruptions.

You can verify that the RTD is faulty by determining the pressure value.

The pressure regulator is checked first, because it is due to its malfunction that the pressure drops. If it is in order, you need to test the operation of the pump. This is done by squeezing the fuel drain check valve.

Video: how to check fuel rail pressure

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Causes of fuel regulator malfunction

In fact, there are not many reasons why the fuel pressure regulator has failed. Let's list them in order:

• Natural wear and tear . This is the most common reason for RTD failure. As a rule, this happens when the car's mileage is about 100...200 thousand kilometers. A mechanical malfunction of the fuel pressure regulator results in the membrane losing its elasticity, the valve may jam, and the spring weakens over time.
• Defective parts . This does not happen so often, but often there are defects on products from domestic manufacturers. Therefore, it is advisable to buy original spare parts from imported manufacturers or check them before purchasing (be sure to pay attention to the warranty).
• Poor quality fuel . Unfortunately, domestic gasoline and diesel fuel often contain excessive moisture, as well as debris and harmful chemical elements. Due to moisture, rust spots may appear on the metal elements of the regulator, which spread over time and interfere with its normal operation, for example, the spring weakens.
• Clogged fuel filter . If there is a large amount of debris in the fuel system, it will also lead to clogging of the RTD. Most often, in such cases, the valve begins to jam or the spring wears out.

As a rule, if the fuel pressure regulator is faulty, it is not repaired, but replaced with a new one. However, before throwing it away, in some cases (especially when talking), you can try cleaning the RTD.

Main elements of the fuel system of an injection engine

The injector is a complex mechanism for supplying fuel to the cylinders. The entire fuel supply process is controlled by the engine's electronic control unit (ECU). The fuel supply system also uses a parallel air supply.

Fuel pump glass

The fuel pump cup is a collection of the main elements of the fuel system assembled on one site.

The fuel pump glass includes:

• Gasoline pump
• Coarse filter
• Fuel level sensor
• Fuel pressure regulator (only in 1.6 liter engine versions)

Gasoline pump

It is one of the main elements of the fuel system. Serves to supply fuel to the cylinder block under pressure. A fuel pump is a kind of electric motor. Its operation is based on the principle of centrifugal force. Under the influence of the magnetic field formed in the stator of an electric motor, its armature is given rotation. A pump volute is installed on the anchor shaft, which directly pumps pressure into the fuel system.

The gasoline pump is very capricious and picky about the purity of the fuel consumed. Most often, the fuel pump fails due to low-quality fuel or its lack in the tank. In order for the gas pump to last as long as possible, it is necessary to refuel at proven gas stations and keep at least 25% of the tank volume in the car’s tank. If you drive with the fuel light on, the fuel pump will most likely fail much faster, since if there are bumps, the gasoline in the tank will squish from side to side and the fuel pump will suck in air.

Injectors and fuel rail

The fuel rail serves as a kind of case for the injectors; it is in it that they are installed.

The injectors of an injection engine are also one of the most important elements of the fuel system. Designed to supply fuel to the engine cylinder block under pressure. The injector sprays fuel into small droplets for better and easier ignition in the cylinder.

The injector is installed directly on the car engine, namely in the cylinder head. The number of injectors depends on the number of cylinders of the car. Lada cars have 4 cylinders, therefore there will also be 4 injectors.

Injectors are also very sensitive to fuel, but are less susceptible to damage since the fuel supplied to them is filtered through 2 filters: a coarse filter and a fine filter. But more about them a little later.

Fuel pressure control

The fuel pressure regulator (FPR) is a sensor installed on the fuel rail in 1.5-liter engine versions and installed in the tank on the fuel pump cup in 1.6-liter engine versions. It serves to ensure the required fuel pressure in the system and regulates the fuel pressure by releasing excess fuel pressure into the return line.

The RTD is a very reliable element and fails extremely rarely. The cause of its breakdown may also be poor quality fuel or the aging factor.

Fuel line

A fuel line is a set of fuel pipes designed to transport fuel from the tank to the internal combustion engine. The highway in Lada is located under the bottom of the car and is protected by plastic covers.

VAZ 2109 injector diagram: how it works

In 1997, they began producing 2109-20 cars, which are equipped with an engine with a distributed injection system (injector). This improves their efficiency, environmental and traction performance. Distributed injection is so called because fuel is injected directly into each cylinder by a separate injector.

Such a system makes it possible to somewhat reduce the toxicity of exhaust gases, as well as improve the driving performance of the 2109 car. Today, there are injection systems without feedback and with feedback. Both presented systems can include domestic and imported components. Each of the systems has its own design, repair and diagnostic features. I would just like to note the main principles of the design, normal operation, engine repair (if necessary) and subsequent diagnostics of the fuel injection system (the VAZ 2109 injector diagram is presented below).

The automotive fuel injection system, which has feedback, is used mainly on export VAZ 2109. The exhaust system of these cars is equipped with a catalytic converter for exhaust gases and an oxygen sensor. It provides feedback. Using an oxygen sensor, the oxygen concentration in already exhaust gases is monitored.

Next, the electronic control unit (ECU) of the vehicle, according to its signals, maintains the appropriate ratio of fuel and air, that is, one at which the special converter works extremely efficiently. The injection system, in which there is no feedback, is not equipped with a converter and an oxygen sensor.

Their function (regulating the concentration of CO in already completely exhausted gases) is performed by a CO potentiometer. They also do not use a gasoline vapor recovery system.