How to find air leaks at home. How to find air leaks in the engine Air leaks symptoms of a VAZ 2114

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In the event that the fuel system of a diesel engine is airborne, the malfunction can manifest itself both constantly during starts after a long idle period, and may not remind of itself for a long time. It depends on the intensity of the air intake. The main symptoms of air entering the diesel fuel system, regardless of the modification of the power unit, are:

the diesel engine is easy to start "cold", but further work is not stable;
, reactions to pressing the gas pedal become sluggish and slow;
after parking, the unit must be turned with the starter for longer and longer, then seizure occurs and the symptoms described in the first case repeat.
as the malfunction progresses, the diesel engine from the starter no longer starts, it is not always possible to start the engine even with the help of starting devices or a jerk in tow;

For a more accurate determination that the cause of the problem start is precisely the air in the diesel fuel system, it is necessary to visually analyze the flow of fuel into the cylinders. For this, the diesel engine takes from 30 to 50 sec. you need to turn the starter to fill the exhaust tract with exhaust, and then analyze the exhaust gases.

If the fuel supply is normal, then even with the fact that the engine does not start, a small amount of smoke will still come out of the exhaust system. Smoke will often have a grayish tint. In rare cases, smoke can occur even in the absence of fuel supply. This suggests that an excess amount of oil gets into the cylinders, but this is the case. It should be noted that this malfunction can be diagnosed by the color of the exhaust only conditionally.

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Possible air leaks

Airing of the fuel supply system can occur both unexpectedly and as a result of recent repairs. Air can enter the diesel fuel system from different places, and the total number of potential "windows" will directly depend on how many years the vehicle has been in operation and in what conditions a particular vehicle is operated.

The fuel system is breathed in both when there is a loss of tightness in the main line, and in the return. Loss of seals in the lines causes the diesel fuel to drain back into the fuel tank. The engine can start after a standstill due to the fact that fuel remains in the cavities, but then the diesel quickly stalls and does not start again.

Air in the fuel system of a diesel engine may be due to the fact that the seal of the connections is broken, the rubber fuel hoses are cracked, the clamps are damaged. Also, fuel lines can suffer from corrosion, especially at the junction with the fuel filter.

Airing can be caused by improper seals on the fuel priming pump. Special attention should be paid to the line for the backflow of fuel on the injectors (return line), since a violation of the tightness of the fuel lines in this section becomes a frequent phenomenon.

Another place for air to enter the fuel supply system may be the fuel pump itself. Violation of the drive shaft seal or pump cover will lead to air leakage from the injection pump. Also in the design there are other places on the pump that can pass air. We add that diagnostics of the high pressure fuel pump must be carried out by specialists in the repair of diesel equipment.

How to detect air leaks yourself: lines, high pressure fuel pumps, return

The exclusion of other possible causes suggests the presence of air leakage into the fuel line. It is necessary to start troubleshooting with a detailed visual inspection of the engine compartment. The next step is to inspect the bottom of the car. It is quite easy to find noticeable cracks and other defects in pipelines, diesel drips and wet spots.

If the system is airing, but there are no obvious signs of leakage, then for further diagnostics it is necessary to disconnect the fuel pump from the fuel lines. Then you will need a separate clean container, into which you will need to pour up to 5 liters of diesel fuel without any impurities. You will also need 2 clean inside and outside hoses (about 60 cm in length), and two more clamps. Remember that cleanliness is extremely important during any work with fuel equipment, since the smallest particles of debris entering the pump can lead to its failure and subsequent costly repairs.

After disconnecting the fuel supply line and return line from the high-pressure fuel pump, prepared hoses are installed in their place, which are lowered into a container filled with clean diesel fuel. Next, you need to fix the hoses in the container so that they do not move. To do this, we attach them to the pump with clamps, and in a separate fuel container in any convenient way, depending on the type of container used.

After that, it is necessary to remove air from the fuel chamber of the pump. Note that the decision to simply turn the motor with a starter so that the pump begins to suck diesel fuel from the container on its own is wrong and is strongly discouraged. There are several correct ways to solve the problem. The following are the simplest ones that will help answer the question of how to remove air from a diesel fuel injection pump right in your garage.

To do this, the container with diesel fuel must be raised above the level at which the injection pump is located. Next, you need to find the place where the fuel return pipe is located on the pump. This place will need to be thoroughly washed to exclude any ingress of dirt. Then the bolt of the union can be unscrewed, and air can be pumped out through the opened hole. Evacuation is performed with a syringe, a special vacuum pump, etc. The air is pumped out until diesel fuel appears from the hole. After that, you can screw the bolt into place and start the engine for a couple of minutes. Start-up is required for final air removal.

The second method is the decision to remove the fuel supply hose from the pump and start sucking fuel until it comes out in a dense stream. Then the hose can be put on the fuel pump fitting and crimped with a clamp. Then the bolt on the return line union is unscrewed, and the air comes out on its own. After all the procedures, the diesel engine is started for a few minutes to completely remove the remaining air from the pump. The launch can be repeated again after some time.

At the end, the container with diesel fuel is placed above the pump level. Then the car is left for 8-10 hours. If, after idle time, the diesel engine starts up normally, this indicates that air enters the fuel system, and this happens through the fuel line. The next stage of diagnostics is the placement of a container with diesel fuel so that it is below the level of the injection pump. After that, the car is left again for 8-10 hours. If, after idle time, the diesel engine does not start or the start is accompanied by problems, then air leaks through the pump or the "return" lines on the diesel injectors are likely.

In the second case, it is necessary to take into account that, structurally, not in all diesel engines, the return line from the injectors is output to the injection pump. The place of removal can be a fuel filter, a fuel filter line. If this is the case, then the method for diagnosing the return flow of injectors described below can be omitted.

To clarify the location of the malfunction, we start the diesel engine and expel the air. Place the fuel tank below the pump level again. The pipes that are responsible for the return flow of the injectors and are connected to the fuel pump must be tightly squeezed. You can leave the car again for 8-10 hours. If the diesel engine starts up normally after idle and runs stably, then air is sucked in through the return line of the diesel injectors. In the event that the problems that arose earlier when trying to start the engine appeared again, then this indicates air leakage through the injection pump. In case of such a malfunction, the pump requires repair in a specialized workshop. It is also not uncommon for cases when in the process of diagnostics several places are revealed at once where the tightness is broken.

In the process of finding a place for airing, the fuel filter is also checked. The verification is carried out according to the scheme: a container with diesel fuel - a fuel filter - a high-pressure fuel pump. The fuel container is placed below the pump level. If no leakage in the fuel filter is detected, the booster pump is checked for leaks in a similar way.

The absence of obvious problems with the fuel pump, booster pump, injector return and fuel lines may indicate air entering the diesel fuel system through the fuel tank. For a more accurate diagnosis, you need to contact a service station, where specialists will carry out a tightness test using highly specialized professional equipment.

Essence and symptoms

The essence of the malfunction

When there is a leak in the intake manifold, much more air begins to flow into the engine than it should. Naturally, this negatively affects the operation of the entire system.

Important! The result of air leakage in the intake manifold is a lean air-fuel mixture.

When this symptom is activated, the motor starts to work unstably. Depending on the severity of the breakdown, the list of possible symptoms can vary greatly. Therefore, it is not so easy to detect a malfunction.

Symptoms of engine suction

Over the years, car owners and automotive experts have compiled a whole list of symptoms that may indicate that the engine is sucking air through the intake manifold:

The engine runs unstable at idle. With this symptom, you simply cannot set the idle speed below 1000 rpm. Each attempt will turn off the motor.
Temperature changes. The engine will start to overheat frequently. Plus it won't depend on the riding mode you choose.
Startup difficulties will be especially noticeable in the morning.
At low revs, the engine power will drop dramatically. At less than 2000 rpm, the car will not be able to develop speed.
Fuel consumption will increase significantly.
When driving at 2000 rpm and more, there are no problems.

Each of these symptoms indicates that there is an air leak in the intake manifold. Therefore, if at least one of them is found, it is necessary to carry out detailed diagnostics and determine the malfunction.

We carry out diagnostics and eliminate the suction

Start the engine first. It should be idling. Then listen to the operation of the device. Highly you can often hear the characteristic hiss of air.

Attention! You can find the breakdown by the source of the hiss.

In some cases, it is not immediately possible to localize the source of the noise. In this case, you will need to pinch the hoses that connect to the manifold. In most situations, problems are observed with the vacuum hose, which is responsible for strengthening the brakes. But exceptions are possible.

Occasionally, a power surge may occur when the clamp is removed. In this case, the problem lies precisely in this detail. Usually, this indicates such malfunctions as:

breakage of the adsorber valve,
failure of the vacuum amplifier,
holes in the hose.

If, after the performed manipulations, the problem is not found, it is necessary to use a sprayer. A flammable liquid is poured into it. It is best to use special carburetor cleaners.

Spray fluids with a thin construction site on potential places through which air is supposed to leak into the intake manifold. Special care must be taken to process:

cylinder head joint,
collector joint,
corrugation,
receiver seams,
throttle pipe joint.

As soon as the liquid enters the damaged area, it is drawn in and ends up in the motor. In this case, you will observe a jump in revolutions.

The most effective method

In order to use this technique for detecting air leakage in the manifold, you need to find a smoke generator. Then select any opening of the intake tract and through it, slowly begin to pump smoke into the system.

Attention! It is better to use engine oil as a consumable; it provides a large amount of smoke.

Further, to find air leakage in the intake manifold, take a halogen lamp. With its help, you can easily find wisps of smoke. You will need special adapters for the procedure.

Eliminating the malfunction

Much depends on where you find air leaks in the manifold. For example, if the hole in the hose is small, you can use a sealant and cover up the damage. Of course, ideally, the damaged element needs to be replaced. Very often this operation must be done with couplings, o-rings and gaskets.

Outcomes

Air leaks through the intake manifold are easiest to diagnose with a smoke generator. Elimination of the defect directly depends on where exactly the breakdown was found.

A gasoline engine requires an accurate fuel to oxygen ratio to function properly. Air leakage in the intake manifold leads to an increase in the proportion of oxidant, which, of course, is registered by the engine ECU (). Consider the main causes and symptoms of the malfunction, as well as how to find a leak in the intake tract using a smoke generator.

Symptoms

Unstable engine idling. At idle speed, the mechanical throttle valve is closed, and air enters the intake manifold through the DZ bypass channel. In this mode, the vacuum behind the throttle is maximum, so the symptoms of air leakage are most pronounced. By opening the throttle valve, we increase the flow area for the air flow, so the negative effect of suction on engine performance is reduced.
Increased idle speed.
Unstable engine operation after a sudden gas release ().
Check Engine lights up on the dashboard due to the P0171 code - poor mixture. You can read error codes through the diagnostic connector with a multibrand scanner with suitable software or a specialized diagnostic tool. If, after removal, the error reappears at idle, it is highly likely that the reason is precisely the air leak, and not the breakdown of the mass air flow sensor, the oxygen sensor.

It should be borne in mind that, individually, each of the symptoms does not yet indicate a leaking of unaccounted for air and can be caused by malfunctions in the power supply system, mass air flow sensor, IAC, throttle unit or lambda probe.

Influence on engine performance

The cause of the symptoms of air leakage lies in the unaccounted for oxygen entering the cylinders. It's time to remember. The sensor is installed behind the air filter. Therefore, the ECU can only calculate the flow passed through the heating element. Leakage is spoken of when there is a leak in the intake tract behind the mass air flow sensor, through which unaccounted air is sucked into the intake manifold. Since the ECU calculates the portion of fuel based on the readings of the mass air flow sensor, the mixture at idle turns out to be lean (excess oxidizer).

In systems with a MAP sensor (MAP), the ECU relies on the pressure in the intake manifold. But for normal operation, the flow area of the bypass channel, which is controlled by the extension of the IAC rod, and the degree of opening of the throttle valve must correspond to the calibrations laid down in the engine ECU. Of course, the suction of unaccounted air introduces confusion in the operation of the control unit, so it tries in every possible way to synchronize the operation of the actuators and the sensor readings. Therefore, the revs begin to float, and in general the idle is unstable.

Possible leaks in the intake tract

Diagnostic Tool Application

The scanner allows you to determine additional symptoms indicating that the cause of unstable idle speed is precisely in the air leaks.The device will allow you to observe in real time:

lambda probe readings;
throttle opening degree;
idle speed control position;
desired and actual idle speed;
long-term and short-term fuel trims.

In the video, the diagnostician explains exactly how to use these values to diagnose air leaks in the engine.

We localize the reason

Consider the main methods for determining the cause of air leakage without using a smoke generator.

Spraying carburetor cleaner close to intake components. The cleaners contain highly volatile and flammable components. Getting through the place where air is sucked into the cylinders, the cleaner enriches the fuel mixture. In especially critical cases, at such moments, a short-term increase in engine speed is observed. But it is much more reliable to observe the short term fuel trim with a scan tool during the test. The values during the suction of the cleaner will rise, as the lambda probe registers the enrichment of the mixture.
Splashing water. The purpose of the test is to hear the characteristic sound of water being sucked in, which will surely happen at the place of air leakage. For convenience, fill the bottle with water, after making a small hole in the lid. Water the connections of the hoses of the vacuum system liberally, if possible, the place where the cylinder block and the intake manifold meet. Check the area after the throttle valve with special care, since there is vacuum and the risk of suction is highest. But do not completely fill the engine with cold water, and especially the exhaust manifold. A sharp temperature drop can lead to cracking.

Smoke generator test

The meaning of the check is to supply smoke to the intake tract. In places where air is leaked, smoke will come out, which will allow localizing the leak. You can buy a smoke generator or build it yourself. There are plenty of different design options on the Internet, one of which is shown in the video below.

How can a smoke generator find the place of air leakage?

Block the inlet in front of the air filter. If this is not done, the smoke pressure in the intake tract will build up slowly.
Disconnect one of the available vacuum hoses, connect the smoke generator hose instead.

Use a compressor to blow in the smoke. When the system is completely filled, you just have to observe the places of smoke leaks, which can provoke unaccounted for air leaks into the intake manifold.

15 january 2018

In modern electronically controlled internal combustion engines, the amount of air entering the cylinders is strictly taken into account by special sensors. But when the air flow finds an alternative path through a loose connection of parts, the normal operation of the power unit is disrupted due to a significant depletion of the combustible mixture. Determining air leakage in the intake manifold or other places is not an easy task, the symptoms that appear are too similar to many other problems. Nevertheless, the problem of diagnosing this malfunction is quite solvable.

Signs and causes of suction

When a leak develops in the engine, allowing additional air to pass through, the following symptoms are observed:

The first sign is "floating" idle speed. The engine draws in excess air, and the control unit, which analyzes the composition of the exhaust gases using a lambda probe, tries to correctly prepare the fuel mixture. But the DMRV (or DBP) does not take into account a part of the inflow, therefore the speed is unstable (about the signs of a sensor malfunction).
The share of fuel in the combustible mixture decreases, hence the difficult start of the power unit "cold" when enrichment is necessary.
Due to the depletion of the mixture, engine power is lost - the car is harder to get under way and accelerate.
As the driver begins to press harder on the gas pedal and forcibly increase the revs, the fuel consumption increases.

There are several reasons why the tightness of the joints is broken and the engine sucks in air:

deformation of adjacent planes (for example, the intake manifold to the cylinder head) as a result of overheating;
too frequent use of automotive cleaning chemicals that can soften gaskets and sealants;
leaky hoses or clamps on the vacuum take-off pipes in the engine.

On diesel engines, air is sometimes drawn in by the fuel pump through leaks in the line from the tank. In carburetors, the air flow path opens through worn axles and worn out dampers.

Where can air penetrate?

To check for engine leaks, you need to understand where to look. On engines equipped with an injector, air can be sucked in in the following places:

a gasket on the cylinder head flange where the intake manifold is attached;
body of the vacuum brake booster;
vacuum take-off hose for the amplifier;
throttle gasket;
through nozzles with weak sealing rings;
on the idle speed regulator flange;
through the stuck valve of the canister - adsorber.

Worn carburetors, whose seating flange has buckled from high temperatures, often let air flow at the junction with the manifold. The second "sore point" is the throttle valves of both chambers, which become oval as a result of wear. Leakage occurs through the side gaps and causes a spontaneous outflow of gasoline from the main diffuser, which causes the engine to spin up to 2000 rpm at idle speed.

The weak link of a diesel engine is the fuel line from the tank to the high pressure pump. Plastic pipes and clamps lose their tightness over time and the pump, which creates a vacuum in the area, draws air through invisible cracks. It passes through the main line and is fed through the nozzles into the combustion chambers. The main problem is finding the problem: the leaking connections do not leak, since the outside pressure is higher than the inside one.

Fault detection methods

As a rule, the possibility of air penetration through a loose connection is remembered last, when other problems are excluded - failure of sensors, regulators, and so on. Meanwhile, there is a simple way to find air leaks - with the engine running, slowly close the throttle valve with your palm. If the motor does not stall, then a gap has appeared in the area after the mass air flow sensor, into which an additional flow seeps.

Note. Hearing a whistle or hiss at the place of the suction is not an easy task, since the noise of a running motor interferes. Therefore, this diagnostic method is not suitable.

Start the engine and wait for the idle speed to stabilize.
Push at several points the rubber tube leading from the power unit to the amplifier housing.
If the operation of the engine does not change, then there is no suction in this section. An increase in crankshaft speed will indicate a malfunction.

In the same way, check all hoses that take vacuum from the motor. If the speed of the crankshaft changes when squeezing and then releasing the pipes, look for a loose clamp or a crack in the hose.

The compressor will help to find air leaks through the throttle valve, manifold and other engine parts. The delivery hose with the adapter is screwed in in place of any spark plug, then the crankshaft turns to the position when the intake valve of this cylinder is open. Injecting air at a pressure of 4–6 bar, treat all joints with soapy water - bubbles will immediately appear at the problem point.

Fill a 20 cc syringe with 3 gasoline.
Start the engine and wait for the idle speed to level out slightly.
Gently spray petrol on suspicious spots by squeezing fuel directly onto the gaskets.
If the suction goes through the intake manifold, then the pistons will suck in the spilled gasoline along with the air and the speed will increase noticeably. Be careful not to spill fuel on the electrical wiring.

The watering method works equally well for checking the manifold, nozzle seals, and throttle gasket. But it will not work to check the carburetor flaps with a syringe, since you cannot get close to them. To make sure that there is a working out and the formation of side slots, the unit will have to be removed and the walls of the chambers are cleaned of soot.

The line supplying diesel fuel to the injection pump of a diesel engine is more difficult to check. The method using a compressor and soap suds is suitable here, but not every garage has such equipment. We'll have to go along the joints of the entire tube and diagnose the suction by the elimination method. Pouring diesel fuel over the connections is pointless - the effect will be insignificant and you will not hear any changes in the operation of the engine.

One of the newest diagnostic methods involves the use of a special device - a smoke generator. The connection is made, as is the case with the compressor, to the spark plug hole of any cylinder. After starting the smoke generator, it is not difficult to find the point of air penetration. It is recommended to use a halogen lamp to better see the rising plumes of smoke.