Compression measurement in carburetor engine cylinders

05 February 2016 Lada.Online 76 502 10

How to quickly and accurately determine the condition of the engine? Check the compression in the cylinders! Is the engine running rough, you feel a loss of power, the consumption of engine oil or fuel has increased and the car has become difficult to start in cold weather? All of these problems may be caused by low compression in one or more cylinders.

About LADA 2109 engines 1st generation (1987 - 2011)

VAZ 2109 (Lada Samara), popularly known as a nine, is a five-door hatchback, a continuation of the Samara line. It was developed in 1987 using the three-door hatchback VAZ 2108 as a basis. The nine itself became the basis for the creation of the VAZ 21099. The car became widely popular thanks to its rapid design, good engines for those times, as well as a practical five-door body. All this, coupled with its low cost, as well as a wide selection of spare parts, made the VAZ 2109 very attractive. This attractiveness was passed on to its successor, the VAZ 2114. In contrast to the VAZ, the injector was installed as standard on the 2109 engines (power unit 2111).

In addition to the injector, the 2109 was equipped with a carburetor with a displacement of 1.1 l, 1.3 l and 1.5 l. Such engines can be seen if you look under the hood of the 2108.

In the article we will look at the engines themselves for the VAZ 2109, their characteristics and weaknesses.

ENGINE VAZ 2108

The 1.3 engine is the base for the eight, it was developed from scratch, and is structurally similar to the 21011 1.3 liter engine. there is nothing in common. This engine became the basis for the creation of power units for installation on the Samara family with a displacement of 1.1 liters and 1.5 liters. This is an in-line carburetor type engine, has 4 cylinders and an overhead camshaft. The timing drive uses a belt.

Regarding the service life of the engine, it is fair to say that careful and quiet operation, proper and constant maintenance will allow you to exceed the official 120 thousand km and the service life can be 180-200 thousand km.

In terms of disadvantages, the following are most often noted. The parts of the cooling system wear out quite quickly. Frequent oil filter replacement and valve adjustment will be required. Oil leaks often occur due to unreliable seals of the valve cover, fuel pump and distributor sensor. It should be noted that unreliable Solex-type carburetors in general, and EPHH in particular.

If the timing belt breaks, the valves may bend. Also, over time, problems with ignition and engine tripping may occur. In addition, due to ignition problems, the engine may detonate. Another reason for this may be low-octane, low-quality fuel. Detonation is indicated by black smoke coming out of the exhaust pipe and loss of power.

ENGINE VAZ 21081

Engine VAZ 21081 1.1 l. is an analogue of the power unit 2108 1.3. However, it has a crankshaft of less stroke, and as a result, reduced traction. This is an in-line carburetor-type engine with four cylinders, an overhead camshaft, and a timing belt. As for the resource, if you ensure careful operation and quality maintenance, you can count on an official 125 thousand km.

Compression in the cylinders of a VAZ 2114 engine 8 valves

The very concept of “compression” denotes the amount of pressure that the engine piston develops at maximum compression of the working mixture, that is, when it is at its lowest point. The higher this parameter, the higher the temperature the fuel-air mixture will burn, which means its consumption will decrease and the overall efficiency of the engine will increase.

Compression measurement for VAZ 2114

The compression of the VAZ 2114, in fact, like the compression on any other car, depends on the following indicators:

1. on the size of the clearance between the cylinder walls and the valves;
2. on the volume of the incoming mixture, which, in turn, depends on the position of the throttle valve and the characteristics of the air filter;
3. from the current engine temperature.

In turn, the size of the gaps between the cylinders and the elements of the piston group can also have a number of reasons:

1. high degree of wear or burning of their walls;
2. incorrectly set clearance between the cylinder walls and the valves;
3. the entry of liquid gasoline into the cylinder (not in the form of a mixture), which causes the oil to be washed away from the walls and the clearance to increase.

Normal compression and its deviations

General cylinder diagram

According to generally accepted standards, the compression of the VAZ 2114 8 valves should ideally be 14 bars (almost 14 atmospheres). The maximum permissible deviation to the lower side is 3 bars (that is, the compression value should not be lower than 11 bar).

True, this is only allowed if the compression value in different cylinders differs by no more than 1 bar. That is, the following compression schemes are acceptable in four cylinders: 12-12-11-12, 12-11-12-11 and so on. If the pressure difference exceeds 1 bar, then such an engine must be urgently repaired.

For example: 11-14-12-8.

Also, it should be remembered that increased compression is no less evil than low compression or compression with a large variation in the cylinders. Thus, increased pressure in the cylinders of the VAZ 2114 can cause high load on engine components, deposit of carbon deposits on the cylinder walls, and ultimately lead to complete engine failure.

Thus, the normal compression should be in the range from 14 to 11 bar, and have a variation from cylinder to cylinder of no more than 1 bar.

In most cases, only new engines have an ideal compression of 14 atm. Even after short-term use, it can quickly drop by 1-2 units - this is considered quite normal. With further wear, it will begin to sag even more, and the wear itself will proceed differently in all cylinders, which will ultimately lead to a large variation in pressure in them.

Measuring compression in the cylinders of a carburetor car engine: 8 comments

Compressions need to be changed by removing the spark plugs one at a time. Because by unscrewing all the spark plugs, the crankshaft rotation speed increases and the compression gauge readings will be incorrect.

I have similar pressure, I think the reason for the high readings is the valve seals (small portion of oil + readings increase), they practically do not last long.

Thanks, I forgot about this little detail. The statistics of the last three measurements are as follows: decoking1 12.3 12.3 13.4 12.7 after decoking 2 12.3 12.1 13 12.5 measurement after changing the oil this year 12.3 12.3 14 13 the compression meter is the same.

The high compression in the third cylinder is really confusing. Perhaps with increasing mileage of the car, for example, at the next oil change, it will level out. Additionally, check the small branch of the boat's ventilation (the fitting on the valve cover, the tube from it, the fitting and the channel into the throttle space on the carburetor).

The car was driven by an elderly person, he was driving very slowly, I had to change the oil, having previously unbraced it, drive it at high speeds - the result was that the compression leveled out, but the third cylinder was completely stuck and did not want to change the value. Thanks in advance for your opinion. An excellent site, taught a lot and made CO CH students independent from grief.

clutch? well, it was turned on for all 4 measurements (i.e. the pedal was not pressed) I’m ready to drive quietly and not pay attention to it, but the presence of a stable couple of drops of oil on the cover of the air filter housing every 1,000 km does not seem like much, but and it shouldn’t be (I cleaned the mesh, the pipes are still like new)

Try again to measure the compression, with the clutch pedal pressed and with it not pressed. Perhaps the numbers will level out. And so, you described an almost serviceable engine with excellent compression, I would drive it like that and not change anything. For prevention, I would change the engine oil.

I measured the compression according to the methodology - 12.3 12.5 14 13, the compression is 14, the engine 2108 has less than 50,000 km mileage! a couple of points from observations, on the cover of the air filter housing after a couple of thousand mileage - a couple of drops of oil from the crankcase ventilation. A couple of times I observed light smoke from the exhaust during intense acceleration, but it does not smoke at all, there is no oil consumption, the spark plug in the 3rd cylinder was a little darker before decarbonization, but now it is the same. What to do ? After all, the spread is more than 1.5. Thank you

If a measurement with a compression meter shows reduced compression in some VAZ 2108 2109 21099 cylinder (cylinders), then the reason can be found by supplying compressed air to the engine cylinder. It is necessary to install the cylinder piston at TDC (top dead center). When the piston is at TDC, the intake and exhaust valves are closed. Therefore, if compressed air is supplied to the spark plug hole, then the cause of low compression in the cylinder can be determined (the compressed air pressure should be 2-3 atmospheres). 1) Air comes out through the engine breather. This means that there is no compression due to a burnt-out piston or worn piston rings. 2) Air exits into the muffler. Here the situation is different, the combustion chamber, which must be sealed, allows air into the exhaust system. This may be due to the fact that the exhaust valve of this cylinder is burnt out, cracked, or stuck. 3) Air enters the engine cooling system, and antifreeze begins to boil, which can be seen in the expansion tank. The reason for air getting into the antifreeze is a burnt-out cylinder head gasket. 4) Air passes into the carburetor (it begins to bubble and hiss). If you have an injection power system, then you may not be able to clearly hear the air leaving through the air intake. The problem in this case will be in the intake valve, which is either burned out or stuck.

When else is this method useful?

Perhaps piston wear in one cylinder is rare, but the valve is pinched - this is a fairly common occurrence. And when the engine heats up, the clamped valve will simply burn out. And if it turns out to be understretched, then strumming sounds will be heard. This is where this method of checking compression without tools comes to the rescue.

Therefore, if you have been adjusting valves, but do not have much experience in this matter, then after adjusting the valves, perform the described operation twice, once on a cold engine, the second time, heat the car to 85-90 degrees and repeat the procedure. When the valves are adjusted incorrectly, but on some cylinder the compression disappears, there will be almost no compression, this means that you have overtightened the valve. We urgently open the lid, adjust the valve and go.

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Poor compression in the engine

The car's behavior has changed. The engine does not start from the first crank with the starter or requires prolonged rotation, and at sub-zero ambient temperatures it may not start at all. If you unscrew the spark plugs and inspect them visually, the reason for the failure to start becomes clear - the spark plugs are “wet” due to an excess of fuel entering the cylinders. These are symptoms of poor compression in the engine.

Signs

• the engine starts, after warming up it idles smoothly, but when driving there is a loss of power;
• failures during acceleration and increased fuel consumption;
• works with misfires - “troit”.

What to do if the above symptoms are identified

In order to avoid further and rapid wear, it is necessary to establish the causes as soon as possible and identify components that need to be repaired.

Based on the results of compression measurements, the following indicators are possible:

• high - more than 15;
• low - less than 12;
• no - 0.

An increase in compression in the engine is visible in the exhaust gases - the color becomes bluish-white and oil consumption increases. When accelerating, the piston pins ring. High compression causes an increase in carbon deposits on the valve plates and guides, and a layer of coke forms on the walls of the combustion chamber, reducing the volume of the chamber and accordingly changing the compression ratio of the cylinders.

High compression gradually causes engine detonation knocks, which destroy the connecting rod and piston group.

Reason for high compression

Analysis of the engine revision shows that there is more than one reason. The table shows the reasons for increased compression in the engine:

Reason for low compression

Weak compression is detected when it is started, especially in cold weather, and signs are also found in loss of dynamics and increased fuel consumption.

Low compression increases the rate of engine wear, and if the defect is in one cylinder, then the idle speed is unstable, the car often stalls or lowers the idle speed.

The table shows the main reasons:

If there is no compression in one or more cylinders, then the engine starts very poorly, and once started, it immediately begins to work unbalanced, with strong vibrations and shaking.

If compression is lost in all cylinders at the same time, the engine will not start. One of the reasons may be a broken timing belt while the engine is running and a collision of the piston with the valves. After an impact the valves bend. The gas distribution system loses its tightness, and the compressed air-fuel mixture is directed at high speed into the intake and exhaust manifolds.

Compression also disappears in one of the cylinders due to severe burning of the valve disc. There are examples when from 40 to 50% of the valve disc area is melted and compression is zero. This is easy to determine without a compression gauge. It is enough to wrap a spark plug in this cylinder and when cranked by the starter, the crankshaft will rotate easily and uniformly, without highlighting the compression strokes.

When measuring compression, it is advisable to observe the needle of the pressure meter (pressure gauge) and monitor the dynamics of its increase. By the rate of increase in compression, you can indirectly determine in which group of parts there is severe wear. If on the first stroke the pressure gauge shows low compression (3-5 atm), and during subsequent strokes the rate of pressure increase increases, then with a high probability it can be established that the piston rings are worn out. To double-check the readings, you can use the method of artificially creating an oil film on the cylinder wall by adding 5-10 ml of oil through the spark plug hole. If, with added oil, the compression increases sharply on the first stroke and settles at nominal, then we can specifically state that the compression rings are worn out. If you measure in two adjacent cylinders and obtain a low result without oil and with oil, you can conclude that there is a defect in the cylinder head gasket.

Another option is also possible, when 6-9 atm is reached on the first stroke and on subsequent strokes the pressure gauge needle hangs in the same position. In this situation, it is assumed that the valve or cylinder head gasket is not tight. You can more accurately determine the cause with other diagnostic devices, such as a pneumatic tester or an electronic oscilloscope.

Measuring compression on a VAZ2109

Start the engine and warm it up to operating temperature. Turn off the engine, remove the spark plugs. Shut off the fuel supply; To do this, you can disconnect the fuel hose and clamp it so that gasoline does not leak out. The throttle and air damper must be fully open. Now firmly insert the compression gauge fitting (or screw it, depending on the model of the device) into the spark plug socket.

Have an assistant turn the crankshaft using the starter. Observe the compression gauge readings and record the readings separately for each cylinder. The minimum permissible compression value in the VAZ2109 cylinders is 10 kg/sq. cm. These values ​​should not differ by more than 1 kg/cm. sq.

If the compression in one of the cylinders is less than the specified number, then there is cause for concern; the reason may lie in wear of the piston rings, insufficient tightness of the cylinder head gasket, poorly ground valves, or wear of the cylinder walls. Almost all of these problems can be solved by overhauling the engine.

Compression measurement: without a compression meter or using special equipment

So, in practice, only two methods are actively used that allow compression measurements to be taken:

Naturally, the presence of a device allows you to obtain the most accurate readings, however, in emergency cases or to obtain approximate estimated results, the decision to measure compression manually is also practiced.

Let us immediately note that in order to measure compression without instruments, certain skills and knowledge will be required, and the operation does not present any great difficulties, even for novice car enthusiasts.

1. First you need to unscrew the spark plugs, leaving only the spark plug in the first cylinder.
2. Then the crankshaft must be turned so that the piston in the first cylinder is at the end of the compression stroke.
3. To accurately determine that the piston is in the correct position, you need to check the marks.
4. Next, you should approximately remember with what force the crankshaft was turned by hand.
5. After this, the spark plug is screwed into the second cylinder and so on.

Note that although the method is quite primitive, in some cases even it allows you to get a general idea and identify a problem in a particular engine cylinder. More accurate measurements can only be made using a compression gauge.

First of all, you need to study the technical documentation in relation to the specific type of internal combustion engine installed on the machine. Having determined the specific compression value for the engine, you need to start the engine and warm it up until it reaches operating temperature (the cooling fan turns on). Then carefully unscrew the spark plugs

Next, you need to invite an assistant who will depress the gas pedal (an important condition when measuring compression) and crank the engine with the starter. If we talk about the device, the compression meter has a special tip that is tightly inserted into the spark plug hole

After this, the engine is cranked by the starter for about 3-4 seconds. It is also important to take into account that you need to measure compression provided that the battery is charged and the starter itself is fully operational. The fact is that insufficient crankshaft rotation speed can lead to a noticeable decrease in performance, but this will not mean that the compression in the engine has dropped so much. Then, when the readings have been obtained, they need to be compared with the nominal values ​​​​for a particular engine.

It is also important to understand that it is not recommended to continue operating an engine in which compression is reduced in one or more cylinders for a long time. The fact is that the parts in this cylinder will wear out even more, the engine itself will vibrate more strongly and operate unstably, unburned fuel will flow into the oil pan in excess, which will cause dilution of the oil, thereby increasing the overall wear of the internal combustion engine, etc.

Forms of manifestation of technical malfunction

Under normal operating conditions, a vehicle consumes a normal amount of oil and fuel. As the piston rings wear out, the iron horse shows clear signs indicating the need for technical inspection:

• reduced engine speed;
• thick black smoke comes from the muffler;
• increased consumption of fuel and lubricants per 100 km of track;
• a specific hum appears.

The above symptoms require measuring the compression level in the engine using special tools:

• a wrench used to align spark plugs;
• compression gauge;
• syringe;
• 30 ml machine oil.

Before starting the measuring procedure, valves 2109 must be adjusted correctly. If you do not have sufficient experience in this, the operating instructions will come to the rescue.

The slightest inaccuracy will lead to incorrect measurement results. Direct measurement occurs in 2 ways:

1. Manually. This method requires practical experience. The use of devices is associated with the car owner’s ability to correctly assess the dynamics of changes in readings. All spark plugs (except for the first) on the cylinder are turned out. After this, you need to slowly turn the crankshaft until the compression stroke disappears in cylinder No. 1. Then you must sequentially unscrew the remaining candles in the same way. The cylinder where the most effort is put into removal is the defective one.
2. Compressometer. Using the device allows you to quickly obtain the value of the compression level in the cylinders. Measurement begins only after checking the reliability of the connections between the motor and the device. The crankshaft rotation speed when measured is at least 100 rpm.

Even a slight deviation of the indicator from the norm is a reason for investigation. For the most accurate measurements, they are carried out on a hot engine (at a temperature not lower than 80 ºС). After turning it on and warming up, it is necessary to remove the candles as described above. An objective assessment of the compression level can only be made with the throttle valve fully open. In some cases, outside help will be required.

Measuring compression in the cylinders of an injection engine

To carry out the work you will need a compression gauge and an assistant.

— Before measuring compression, it is advisable to check the clearances in the engine valve mechanism and fully charge the battery.

— Warm up the engine to operating temperature.

— Place the car on a level surface, raise the handbrake, select neutral gear.

— We take out the three fuses of the engine management system (ECM) and the control unit (ECU).

The ECM fuse and relay box on VAZ 2108, 2109, 21099 vehicles with an injection engine is located under the instrument panel on the right side and is closed with a lid.

— We turn out all the spark plugs.

The procedure for measuring compression in the cylinders of an injection engine

— We insert the compression gauge into the spark plug hole (either press it or screw it in, depending on its design).

— An assistant presses the gas pedal all the way and turns on the starter for 4–5 seconds.

— We remember, or better yet, write down the compression meter readings and the order of their increase.

— We reset the compression meter readings.

— We check the compression in other cylinders in the same way.

If the engine is working properly, the compression gauge readings should be within 1.0 MPa (10 bar), and the difference in compression between the cylinders should not be more than 0.1 - 0.15 MPa.

Notes and additions

— If the readings on the cylinders are below normal, then we do the following: using a medical syringe, pour 10-15 cubes of engine oil into each cylinder through the spark plug hole and measure the compression again. The indicators have increased - this means the problem is in the rings (stuck, worn out, broken), if not - the problem is in the valves (burnt out, not sealed, large gaps) or in a burnt-out head gasket.

More articles on VAZ 2108, 2109, 21099 engines

What and how to measure compression?

As noted above, measuring compression is a simple operation, and it can easily be performed in a garage.

But for this you need a special measuring device - a compression meter.

In fact, this is a regular pressure gauge, equipped with a check valve, as well as an extension cord for ease of diagnostics (the kit may also include attachments for working with different power plants).

In addition to this, the device will also require a spark plug wrench. You won’t be able to diagnose it yourself, so you also need an assistant.

Let's look at how compression measurements are made using the example of a VAZ Kalina car.

The sequence of actions for diagnostics is as follows:

1. Warm up the engine to operating temperature;
2. We relieve the pressure in the fuel rail (pull out the fuel pump fuse, and then start the engine again so that it produces the remaining gasoline in the rail);
3. We remove the tips of the spark plugs, as well as from the ignition module;

4. We unscrew all the spark plugs;

5. We install a compression gauge in the spark plug hole of the cylinder;

6. We ask the assistant to press the gas pedal all the way (this will ensure maximum air supply to the cylinder, which will make the readings more accurate), and then turn on the starter. In this case, to obtain correct data, it is necessary that all 4 strokes have passed in the cylinder being measured, that is, you need to turn the crankshaft at least 2 turns;
7. Since the compression meter has a check valve, the device will record the maximum pressure value in the cylinder;
8. We write down or remember the obtained pressure value, reset the readings and move on to the next cylinder.

After taking measurements in all cylinders, we compare the data. If the difference in readings does not exceed 1 kgf/cm2, put the spark plugs in place and continue operating the car.

COMPRESSION – WHAT IS IT AND WHAT SHOULD IT BE?

Compression is a measure of the maximum pressure in the combustion chamber that the piston can create when it reaches TDC during the compression stroke. Measuring this indicator gives an idea of ​​the tightness of the chamber, which in turn depends on the condition of a number of elements - the piston and compression rings, valves with seats, head gasket, and the installed thermal gap in the timing belt. Since the compression measurement technology itself is simple, and the data obtained as a result of its implementation makes it possible to estimate the remaining life of the power plant and identify a number of malfunctions, this diagnostic operation is quite common.

Although car power plants have a common design principle, they are structurally different, which also affects compression indicators. Each engine has its own specific maximum pressure values ​​in the combustion chambers, which must be indicated in the technical specifications. documentation for the car. For example, for a VAZ-2106 a compression of 11 kgf/cm2 is considered normal, but for a VAZ-2110 this figure is already 13 kgf/cm2.

Note that when measuring, it is not necessary that the device should show values ​​that correspond to the norm. As engine components wear, compression readings will drop. Moreover, if they drop below a certain value, this will be a signal of extreme wear of the power plant’s CPG, and the need for major repairs. Some variation in readings between cylinders is also allowed. However, it should not exceed 1 kgf/cm. sq. That is, if measurements on a VAZ-2115 showed that the compression in the cylinders was 12 kgf in the 1st, 11 kgf in the 2nd, 12 kgf in the 3rd, 12 kgf in the 4th, then the power plant of the car will be considered to be in working order.

REASONS FOR COMPRESSION FALL IN ONE CYLINDER

It also happens that a pressure drop occurs in one of the cylinders, and significantly (in some cases, compression can drop to 3-4 kgf/cm2). And such diagnostic results are a reason to worry, because there are malfunctions in the power plant.

The reasons for a drop in compression in one of the cylinders above normal may be:

COMPRESSION RINGS. These elements play one of the most important roles, since their task is to ensure tightness in the piston-cylinder pair. If the rings are damaged (burst) or stuck, they will begin to leak working gases into the sub-piston space, which is why a significant drop in compression occurs;

VALVES. Through these elements, the components of the combustible mixture are admitted and exhaust gases are removed. But during the compression stroke, the valves are closed, which seals the combustion chamber. But if, due to a violation of the combustion processes, the edge of the valve plate and seat are burnt, or the thermal gap is broken, and it turns out to be slightly pressed, then the tightness of the chamber is not maintained, which affects the compression;

PISTON. This element is rarely to blame for a drop in pressure in the cylinder, but there are still situations when the reason lies precisely in it. As a result of the same process changes, the piston crown may burn out. This usually happens due to a violation of the ignition angle. And if the piston burns out, then there will be no tightness;

BLOCK HEAD. Although rare, it does happen that cracks and other defects appear in the combustion chamber, affecting the loss of compression. Also, the head can cause a loss of pressure in some cylinder if it fails due to overheating. Due to changes in geometry, the head in some places simply does not fit tightly to the gasket. Even a simple insufficient tightening of the cylinder head bolts can affect compression;

cylinder head gasket. Due to internal defects or overheating, a breakdown of this gasket may occur. As a result, one of the cylinders is connected to a channel of the cooling or lubrication system, another cylinder (in this case, a strong drop in compression is observed in two cylinders), and the breakdown can also lead out of the engine.

What is compression and symptoms of problems with it

Compression is the value of the maximum pressure in the cylinder, which occurs at the very end of the compression stroke of the mixture, when the piston (see Replacing pistons on a VAZ on your own) in the cylinder reaches its top dead center (abbreviated TDC). Compression is measured with a special device - a compression meter. It consists of a pressure gauge connected to a pressure gauge by a flexible hose (or metal tube) at the other end of which there is a fitting. The signs of a problem with compression have already been mentioned above, now we will give a complete list of symptoms that the engine compression on a VAZ 2109 has dropped to make it easier to identify this particular malfunction. Remember, bad compression is:

• Increased fuel consumption.
• Drop (slowdown) of dynamics (acceleration)
• Weak, slow response to the accelerator pedal
• Black exhaust from a pipe
• Weak "traction"

Verification methods

There are two ways to check compression that you can use: an accurate measurement, using a compression gauge, or, in the absence of one, an approximate measurement, that is, manually. The manual measurement method requires some experience, but it is not complicated:

• Take the spark plug key
• We unscrew all the spark plugs, with the exception of the spark plug in the first cylinder, and rotate the crankshaft manually until the compression stroke is completed (this is determined by the coincidence of the valve timing marks)
• We unscrew the spark plug of the first cylinder and screw in the next one in order, again rotate the crankshaft until the compression stroke is completed.
• Repeat the procedure for the remaining cylinders
• You can understand where the compression is weak by comparing the forces applied to rotate the crankshaft

I agree, this is a rather primitive method of measurement associated with a person’s subjective perception. Therefore, we recommend using it; in extreme cases, it is better to use a compression gauge.

Instructions for checking with a compression tester:

• A spark plug wrench and the compression gauge itself will come in handy, of course.
• You can find out the permissible compression value of your car’s engine from the data sheet.
• Before checking the compression in the engine, we check the valve clearances and adjust them if necessary
• Then we warm up the engine to a temperature of about 70-80 degrees
• Stop the engine and unscrew the spark plugs using a spark plug wrench

Attention: Wear gloves, the engine is hot and the spark plugs will be hot.

• Remove the fuel hose and plug it with a plug to prevent fuel from flowing in
• Then remove the central wiring from the ignition coil
• Here you cannot do without an assistant, since the measurement requires full opening of the throttle valve (for this you need to press the gas pedal to the floor), and the assistant will also rotate the engine from the passenger compartment with the starter while you are taking measurements
• If the pedal can be locked, then you cannot turn the starter without an assistant, because you need to hold the device
• We firmly insert the compression gauge fitting into the spark plug hole and check the tightness of the connection

Insert the fitting into the spark plug socket

• Ask an assistant to turn on the starter and turn the crankshaft with it until the readings on the pressure gauge stop increasing (it will take about a couple of seconds)
• The crankshaft must rotate at a speed of at least one hundred revolutions per minute
• This can only be done with a properly charged battery.
• Turn off the starter, look at the pressure gauge readings, remember or write down
• We take measurements for all cylinders
• Don’t forget to bleed the air from the compression meter before each new measurement.
• When the data obtained differs from the norm, we recommend repeating the measurements on this cylinder

If you don’t know what the norm is for your car, you can determine the approximate normal compression of your car using the formula:

• Compression = compression ratio multiplied by ratio
• You will find the compression ratio in the technical specifications of the motor.
• The coefficient depends on the type of motor, it is 1.2-1.3 for four-stroke engines with spark ignition
• The compression of a new car or engine in good condition should match the manufacturer’s data or the data calculated using the formula
• The difference in the compression meter readings obtained should not exceed 10% of the maximum value between all cylinders
• It will look simpler like this: the permissible difference is no more than 1 kgf/cm 2 according to the instrument for a gasoline engine
• A 15% drop in compression in one cylinder indicates wear on the piston, cylinder, valves or piston rings.
• Long-term operation of the engine with such a cylinder leads to increased wear of all other parts.

What compression should be on a VAZ-2109 car

All owners of domestic cars know the first symptoms of problems with the VAZ-2109 engine: poor dynamics, increased gas mileage, partial or almost complete lack of response to the gas pedal, lack of traction, the car moves with great effort, black smoke comes from the exhaust pipe .

First, an experienced driver blames the spark plugs, and then the piston system comes into question. To check the condition of the piston rings, an independent diagnosis of the operation of machine parts is carried out.

To do this, you need to determine the engine compression.

Even if the carburetor is acting up, you need to check the compression first - this approach will allow you to accurately detect faults in the VAZ-2109, eliminate them and proceed to regulating the carburetor.

How to get rid of inaccurate compression measurements

The compression meter may show inaccurate values ​​if at least one of the following factors exists:

• VVAZ-2109 battery is practically not charged;
• a starter malfunction has been detected;
• the engine is cold;
• valve clearances do not correspond to normal values;
• gasoline got into the cylinders;
• The measurements were initially taken incorrectly.

In the absence of an assistant, the procedure was carried out without pressing the gas pedal, which in itself is considered a significant violation of pressure measurement.

Experts note that the compression meter gives increased readings when there is excess oil in the cylinders, this is due to wear of the oil scraper caps built to guide the VAZ-2109 or CPG valve bushings.

Regardless of which mechanism is installed in the VAZ-2109 - a carburetor or an injector - the maximum pressure value is calculated based on the product of the compression ratio and a constant coefficient equal to 1.2.

Boosting with additives: salvation is real, probably confirmed

These additives seem to build up a thin layer on the worn areas of the metal, the thickness of which, however, is sufficient to “replenish” the worn rubbing surfaces of the engine with a certain material, which, moreover, is capable of retaining motor oil. This allows you to further increase the compression in the engine. These additives are available on the consumer market in a fairly wide range, and car enthusiasts can only choose, trusting advertising and the recommendations of friends (if they decide to increase the pressure in the cylinders of their car on their own).

CORRECT COMPRESSION

How much compression should be in the engine for its long-term and trouble-free operation? Long-term practice of operating cars shows that ideally it should be 14 barrels in each cylinder. But a reduction to 11 barrels is allowed, provided that the difference in compression in the cylinders should be no more than 1 barrel. For example, a compression pattern of 11-12-11-12 is considered acceptable, but if the pressure in different cylinders is 11-12-11-9, or another combination of indicators that differs from normal, then the engine already needs repair.

Article on the topic: Replacing the universal joint on a VAZ 2107

What compression should be on a VAZ 2114 8 valve also depends on how long and under what conditions the car is operated. Ideal pressure, as a rule, occurs with a new engine, or one that has just come out of a major overhaul. During vehicle operation, compression may drop by 1-2 barrels. And this will also be within the normal range.

A new engine is the key to good pressure

How to measure engine compression correctly?

Engine compression indicates the condition of the engine, its service life, power, and torque. This procedure must be performed every 20-30 thousand kilometers, as well as before purchasing a car. Even when checking at a service center, YOU will need knowledge of “how to correctly measure compression”, because... Servicemen love to deceive and make money from you.

Let's start with the theory:

Compression is the pressure created in the cylinder at the end of the compression stroke.

Another term is appropriate here: Engine compression ratio.

The engine compression ratio is expressed in the following ratio: compression/combustion chamber volume.

What compression should be in the cylinders of a VAZ engine?

Normal engine compression is at least 10 bar (1.0 MPa), and the difference between the cylinders should not exceed 1 bar (0.1 MPa). If your compression is 11-12-11-12 from cylinders 1 to 4, then the engine is fine, but do not forget to adjust the valves every 2500 km. If you have 11-9-12-11, then you need to look for the reason and make repairs, because Driving in such conditions will only kill the engine.

How much should the ideal compression be?

The ideal compression should be 14 bar for an 8-valve engine in each cylinder with minimal variation (14-14-14-14).

What do we have to do?

First of all, we install the car downhill, in principle, it doesn’t matter what the angle is, ten to fifteen degrees is enough. The most important thing is that the car rolls easily, but there is no need to choose a very steep descent, the test results may be incorrect

How is it checked?

We stopped the car on a descent, engaged second gear, released the clutch and handbrake. Let's note the time. After some time, the compression tightens, the compression is released from the cylinders, but the car, of course, does not start.

We are waiting, after some time there will be such a failure - OP, that’s it, the car started, OP, until the next cylinder, it stopped. We measure the time interval between these dips

. After a while the compression tightened and the car started moving again. And so you need to measure the time four times - unless, of course, you have a four-cylinder engine.

If this distance is equal, plus or minus 10 seconds is allowed, then everything is normal. If some interval turns out to be shorter, then get out of the car, open the hood, open the distributor (if the car is carburetor) and look at where the slider is, on which cylinder the compression is taking place (in the injector you need to look at the timing marks).

Now get into the car and do the same thing, only in ignition order, for example - first and third, fourth and second. As a result, you will know exactly which cylinder has weak compression.

Instructions for checking compression of VAZ-2109

To measure compression, you need to prepare special tools:

• a compression gauge consisting of a soft bendable hose, a pressure release key and a tip with a measurement panel;
• spark plug key.

When diagnosing yourself, you cannot do without an assistant. Instructions for measuring compression of a VAZ-2109 injector and carburetor look like this:

1. Turn on the car engine and heat it to a temperature of 80 to 90 degrees.
2. Remove the hose from the fuel pump that drains gasoline.
3. Carefully unscrew the spark plugs, first clearing the wells of any build-up of dirt and debris.
4. Remove the armor wire located in the center from the toggle switch cover, fix the spark plug in it and place it on top of the engine.
5. Place the compressor tip in the recess of the first cylinder; the device does not have to be screwed in; it can be pressed against the hole with your hands.
6. Proceed to measure pressure. The assistant must take the driver's seat and press the gas pedal all the way, then turn the key in the ignition and start the starter for at least 3-5 seconds.
7. Watch how the compression meter values ​​change at this time, the dynamics of increasing readings should be recorded, and also write down the maximum position of the arrow. Once locking is complete, release the pressure by pressing the release button.
8. These actions must be performed for each engine cylinder separately, so as not to forget the indicators, record them on a piece of paper.

How to get rid of stuck piston rings

If the fault is that the rings are stuck, to repair them, repeat the following steps:

1. Warm up the VAZ-2109 engine.
2. Find a spark plug hole in each cylinder and add 10 cm cubes there using a medical syringe or rubber bulb. a mass consisting of kerosene (occupies half of the total mass), acetone (a quarter of the volume), motor oil (a quarter of the volume).
3. Set the mixture aside for 3-4 hours; if you have time and there is no hurry, it is better to leave it overnight.
4. After this, rotate the starter for 10-15 seconds with the spark plugs turned out.
5. All that remains is to drain the old oil, and after replacing the old filtration device, fill in the new one.

Now that you know what engine cylinder compression should be on a VAZ-2109 and how to determine it yourself, and most importantly, how to eliminate the detected faults, returning the car is not difficult.

A popular way to eliminate stuck rings and increase compression

This method does not guarantee that the compression meter readings will change. But, it is actually effective if different compression in the cylinders was formed precisely because of the position of the rings. At a minimum, your conscience will be clear, and you will then exclude this item from the diagnosis.

We purchase high-quality valve cleaning fluid. The instructions for it should indicate that it is added to engine oil. This evening we unscrew all the candles and pour 50-70 ml into the cylinders. this liquid using a bulb or syringe. In the morning, after 12 hours, crank the engine, then clean the spark plugs and adjust the gaps, and only then screw them into place. When starting the engine, do not be alarmed by the quality and quantity of smoke from the exhaust system. You enter the road to pass sections at higher speeds. That is, the task is to give the engine maximum load. Therefore, think in advance where you will do this. Consider the condition of the road surface, weather conditions, traffic intensity

Ideally, this is done on a country road. Important! The previous point must be fulfilled, otherwise the coking products that have come loose overnight will fall under the valve and then disassembling the cylinder head will not be avoided. After running at a speed of 100-120 km/h over a section of 10-20 km. measure the compression in the cylinders again.

There are two options here: joy and a feeling of happiness from seeing numbers of the same compression, which corresponds to the norm. Or bitterness from the upcoming operation with disassembling the cylinder head and diagnosing the engine. There is no third.

Good luck with eliminating compression differences between the cylinders.

Expert opinion Ruslan Konstantinov Expert on automotive topics. Graduated from Izhevsk State Technical University named after M.T. Kalashnikov, specializing in “Operation of transport and technological machines and complexes.” More than 10 years of professional car repair experience.

If in one of the “pots” the pressure is significantly lower than in the others (for example, everywhere is 11.5, and in the only one 6.0 atmospheres), this indicates a difference in compression. Naturally, this negatively affects the operation of the power unit. Often a drop in compression can be observed in several “pots”. However, in this case, we can safely say that the engine needs urgent overhaul. There can be many reasons for a drop in compression; elimination requires dismantling the cylinder head. Here are the main reasons: 1. Broken (burnt-out) cylinder head gasket. One of the most common causes is “treated” by replacing this element. 2. The cylinder head is not tightened enough. Actually, the above reason follows from this: the gasket begins to leak pressure and eventually breaks through. 3. Rings are skipped. This phenomenon occurs if the o-rings are severely worn or broken. If the pressure drops in one “pot”, the rings are guaranteed to be broken. In this case, a major overhaul of the engine is required. 4. Coking. The rings become coated with coke due to the use of low-quality motor oil or due to high mileage. The oil burns out and the rings stick in one place, unable to move along their grooves. Only one side is ground down, which means the engine wears out faster. Coking is indicated by a drop in compression in all cylinders. 5. Wear of the walls of the cylinder block. This is a rare phenomenon and most often occurs due to the manufacturer using low-quality materials. 6. Engine overheating. If the engine overheats, the rings and the walls of the block begin to leak pressure, and with it the oil. Partially can be identified by the bluish smoke from the exhaust pipe. 7. Piston burnout. If the piston is broken, the compression in the cylinders will be virtually zero. It can burn out from both the top and the side. Often, pistons break when the timing belt breaks when, due to a violation of the valve timing, they meet the valves. 8. Valves. Compression may drop due to improper adjustment, burnout or breakage when the timing belt breaks.

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Evaluation of the information received

The piston rings form a sealing layer. It is located between the pistons themselves and the cylinder. In working condition, piston rings act as engine protection against gases and oil from the combustion chamber entering the crankcase. Depending on the technical malfunction, the problem is diagnosed at the level of increased oil or fuel consumption.

Experienced car enthusiasts recommend checking the data several times when measuring the compression level in the cylinders. The following formula will help in establishing the truth: the compression level (kg/sq.cm) is equal to the compression ratio multiplied by the engine coefficient (the value is taken from the book on the technical operation of the vehicle).

Ideally, the cylinder compression level in new cars is always at the level set by the manufacturer. If after the first visit to the service station the value is very different, then you need to return to the auto center. In some cases, factory defects become the reason for inflated performance of a new car. That is why it is recommended to carefully evaluate a potential purchase at a car dealership.

It would not be amiss to compare the data stated in the book on the technical operation of the vehicle with the actual data.

A test drive will help you do this. Any self-respecting car dealership will offer the client the opportunity to sit behind the wheel of an iron horse before making a purchase. A sharp start, a constantly burning oil level lamp, increased emissions - all of the above indicates existing technical problems.

BG products used for compression restoration

One example of the use of BG products as a preventative measure to keep the cylinder-piston group (combustion chambers, piston, oil rings, valves, etc.) clean is the so-called “great three” BG:

1. Compression restorer working with the oil system - BG 109;
2. Engine oil conditioner BG 110 (BG 115), the task of which is to give the oil thermal and antioxidant stability, protect the required additive package provided by the engine oil manufacturer, and also reduce friction in the engine, thereby increasing the service life;

BG 208 is a highly effective fuel system cleaner for gasoline engines, poured into the fuel tank. Its advantages are that its combustion temperature is much higher than the combustion temperature of the fuel (it does not burn in the combustion chamber). Thanks to this, it cleans the entire fuel system, combustion chamber and exhaust system elements (oxygen sensor, catalyst).

And in conclusion, I would like to remind you that preventing a problem is much easier than solving it. Timely and regular use of auto chemicals when servicing vehicle systems will help you save significantly on its repairs, increase the service life of its components and assemblies, increase engine efficiency, and issues with piston rings will arise only if you communicate with those who neglect these recommendations.

Prevention is cheaper than repair!