How to make a compression gauge for a diesel engine with your own hands?

Why is a compression gauge so necessary?

There are several reasons why it is necessary to measure compression in diesel engines. The compression level is measured in order to determine the technical condition of the parts of the cylinder-piston group and valves. Also, using measurements in real conditions, information about the minimum starting temperature of a cold engine is obtained. Compression measurements are made on both gasoline and diesel internal combustion engines. But in the case of the first units, there are fewer requirements for indicators. With a gasoline engine, they do not always pay attention to small discrepancies in the numbers - these motor units have their own characteristics that do not affect their overall health.

Compression is, on the one hand, a physical quantity. Compression characterizes the force of pressure that is created in the combustion chamber. The main condition is that the measurement is performed with the power turned off. During the measurement process, the crankshaft rotates only with the help of the starter. On the other hand, compression is the level of maximum pressure when the piston is at top dead center.

Do-it-yourself compression tester for gasoline engines

Download file - Do-it-yourself compression tester for gasoline engines

Welcome to the forum of car painters, body repair, car enamel, polishing and painting of the body - everything is on our forum. Car painters forum, body repair, car enamel, body polishing and painting. Please login or register. To the site Home Help Login Registration. Having researched the Internet about the cost of a compression meter, I was surprised - a normal compression meter costs about a hundred pounds of greenery. IgorE Veteran Offline Messages: The cost of a ready-made one on the market, in a beautiful box, will discourage anyone from making a homemade gun. ASDS Guest Offline Messages: The whole feature is contained in the valve, the spring stiffness is selected there. A homemade product will not be accurate. About two years ago I also wanted to start a homemade one. When I found all the information about compression meters, I read how it works. I immediately realized it was better to buy. I only screwed the flexible hose into the spark plug well once. Then I unscrewed it for 2 hours. After that I don't even try. And it’s more convenient with a regular gag. I saw a compression meter with a valve made from a spool from the chamber. We do everything with taste! Dmitriy ShaTUN Veteran Offline Messages: In the near future I am going to acquire a USB oscilloscope. Let's try an alternative to a compression gauge with a pressure sensor. In the meantime, I own this device - The asking price is UAH. The only thing that confuses me is that the rigid tip does not reach the valve wells, but the flexible one. In principle, it screws in and out, but there is not always confidence that this is the case. If you use a hard adapter, will the losses distort the readings? Why did they pile up so many “vegetable gardens”? There is a regular compression gauge, we straighten the tube, make the rubber tip slightly smaller in diameter, and lo and behold, you can crawl into any wells and don’t need to screw anything in. Or do you need to track the pressure drop in the cylinder over time? The compression gauge always has a check valve; it is very inconvenient to work without it. To check for leaks in the combustion chamber there is another device: There is a compression meter for diesel engines, there is a long tube. Which check valve are you talking about? I have a spool from the chamber in the compression tester, I measured it and bled it. And there’s nothing fancy here, or am I mistaken? You turn the engine until the needle stops rising. Toto, I think why the compression meter shows an underestimated compression of the glasses on I got it by accident, apparently the old owner installed a regular spool from the camera, so he began to lie. Even the factory one can lie. For the most part, it is not the absolute readings that are important, but the relative ones - that is, the difference in compression in the cylinders. At what pressure should the spool valve open?

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Do-it-yourself compression meter

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Do-it-yourself compression meter

Operating principle

The diesel-gasoline compression meter works very simply. To begin work, the equipment will be connected to the engine cylinder through the hole of a spark plug or injector. The pressure created in the cylinder is then supplied to the pressure gauge through the open valve. When the pressure in the cylinder decreases, the shut-off valve closes. This happens automatically. The valve maintains pressure in the hose or tube, which allows you to evaluate compression indicators. After completing the measurements, the pressure is released by pressing the button.

The difference between a diesel compression tester and a gasoline one

At first glance, it may seem that a compression tester for a diesel engine is no different from its gasoline counterpart. Indeed, visually the design of the two devices is almost identical. The difference lies in a couple of nuances. Thus, the device intended for measuring compression in diesel engines is designed for high pressure - up to 60 atmospheres and above. This is due to the design features of diesel internal combustion engines.

How to make a device with your own hands

You can purchase a ready-made device. The price of a compression tester for a diesel engine starts from 650 rubles. But at the same time, you can assemble the device with your own hands from what you have at hand. Elements for assembly can easily be found in the garage or at an auto parts store.

For assembly you will need a pressure gauge, a valve from a truck chamber, a nipple, several threaded brass adapters, and a high-pressure hose.

The valve must not have cracks, deformations or other damage. As for the size, it is often 8 millimeters. If it is curved, it should be straightened and trimmed where it will be installed in the camera. There is no need to touch the threaded part. Using a soldering iron, solder the nut on the cut side, and then screw the pressure gauge into it.

In this case, the spool will play the role of a valve. The maximum pressure that occurs in the upper position of the piston will be recorded on the pressure gauge dial. To reset the readings, simply press the spool.

This is the simplest design. But you can make a compression gauge for a diesel engine, which will be no worse than analogues from various manufacturers. In addition, a homemade device will be much cheaper in price.

What is needed for a compression gauge?

Here is a list of the parts you will need to make a compression gauge with your own hands:

Pressure gauge with a measurement range of 0–30 kgf/cm2.
Brass or copper adapter.
Two valves from a truck camera.
Copper or brass tube with an internal diameter of 10–15 mm.
Brass or copper tee with an internal diameter of 8–10 mm.
Rubber nozzle. Instead, you can use a high-pressure rubber hose and a set of adapters for various threads.
Soldering iron.
Gas-burner.
Rosin (flux).
Solder POS 40 or POS 60.

The basis of the compression gauge is a pressure gauge. To check gasoline engines, you can use this device with a scale of up to 15 atmospheres. If you need a universal meter, then the scale should reach 30 atmospheres. This device can be purchased inexpensively at any enterprise where old Soviet trucks remain. It is advisable to check it by connecting it to a pressure source and a reference pressure gauge. This will help determine the error that must be taken into account when checking the motor. Chamber valves are necessary to create check and bleed valves. An adapter, tube and tee are necessary to assemble all the elements into a single whole. The rubber nozzle ensures that the device is firmly pressed against the candle hole.

Compressometer "Friend" (diesel)

This universal measuring device can most often be found on the shelves of car dealerships. It is produced at the Izmerit LLC enterprise. Its cost varies, but not more than one thousand rubles. This compression meter took ninth place in the “Behind the Wheel” rating. Detailed instructions included. The manufacturer provides an unlimited warranty. As for accuracy, it is quite high. The only negative is the check valve. The readings of the Friend diesel compression meter drop to zero in just a few seconds. The valve itself is practically no different from a tire valve. It can be slightly modified to provide an accurate, inexpensive and universal solution for measuring compression in a diesel engine.

How is verification carried out?

compressograph

Diesel compression is the main indicator that allows you to determine the condition of the most important components of the engine system. To identify the condition, each engine has optimal compression indicators compiled taking into account its main features. If during the test a drop in engine compression was detected, this is a strong argument for professional diagnostics of your car. In such a situation, you may need high-quality repairs to restore the function of the car. Therefore, it is necessary to understand how to determine compression readings in the engine. For a successful check, it is necessary to take into account certain subtleties during the work.

Let's look at the relatively simple but really important rules that compression testing requires:

Determining compression on a diesel engine, possibly through the spark plug channels.
Compression can be detected by maintaining the thermal characteristics of the engine. It will not be possible to check the compression of a diesel engine with insufficient heating, since the indicators will be underestimated due to insufficient expansion of the working fluid.
Real test results can only be obtained with the throttle fully open. If the damper is not fully open, the readings will be incorrect.
Before checking, you must make sure that the starter is in full working order and the battery is properly charged.
The check involves completely removing the glow plugs from each working cylinder.

To carry out this operation, you will need one of the two above-mentioned devices (compressometer or compressograph). A compression gauge looks a little different from a pressure gauge. To check, you need to remove the spark plugs and install the device conductors in their position. Next, you need to fully open the throttle and turn the key in the ignition. After the starter turns the crankshaft a couple of times, you need to pay attention to the readings of the measuring device. So, it is necessary to check each cylinder. By checking each cylinder, you can determine the general condition of the CPG. If the compression is normal, then your engine is in completely good condition. In the event of a slight change in compression, you can try to restore engine function using special additives. In case of a significant deviation from the norm, you need to contact professionals; your engine may need to be given due attention.

Thus, we learned how to check the compression in the engine. It is necessary to understand that this parameter is fundamental for a diesel engine. Therefore, to maintain the engine in good condition, check it at least once a month. Good luck with your test results!

King-Tool KA-6640N

If “Friend” took ninth place, then this universal diesel-gasoline compression tester is at the top of the ranking.

Compression in the engine cylinders is the most important characteristic; based on its value, full conclusions can be made about the condition of the main components and mechanisms of the engine. Even the use of an endoscope will not tell you more about the degree of wear of, say, piston rings and cylinder walls - with its help you can only see possible scuffs and cracks in parts. By measuring the pressure in the cylinders, you will immediately understand whether the engine needs serious repairs. You can make a compression meter yourself if you have simple metalworking skills - the device is quite simple, and purchasing a professional compression meter for personal use does not make sense. Before we begin to describe the device itself and how you can make a compression meter yourself, we will provide some necessary information about compression - they will help you navigate the choice of materials and evaluate the data obtained during measurements.

Compression gauge - how to make it yourself

Minimum information about compression

For a diesel engine, in which ignition of the fuel occurs under strong compression, the amount of compression plays a decisive role.

Compression is nothing more than the air pressure in the engine cylinder created by the piston during the compression stroke. As a result of the dynamic compression of the air, it heats up, which promotes better combustion of the fuel that is injected (or sucked) into the cylinder. For a diesel engine, in which ignition of the fuel mixture occurs only due to its strong compression, the amount of compression plays a decisive role - the engine simply will not start if it is below a certain norm. A gasoline engine can operate at lower pressure values, but there is also a certain threshold for it. For clarity, imagine a piston with a burnt-out bottom. The mixture expanding upon ignition will not push it, but will simply break into the crankcase. For diesel engines, a compression of at least 28 kg/cm2 is considered normal; it will allow the engine to start at temperatures as low as 15 degrees and develop acceptable power. However, the best indicator will be a pressure of up to 40 kg/cm2 - this is “ideal”, the engine will start in 35-degree frost and the car will have maximum dynamics and traction.

When choosing a pressure gauge, be guided by its operating range - the scale should exceed the compression limits.

For gasoline engines, compression values are much lower - from 12 to 16 kg/cm2 - depending on the engine model. For both internal combustion engines, the difference in values is allowed no more than 3 kg/cm2, and the number of cylinders also matters - a 6-cylinder engine will “swallow” a large spread much more easily than a 4-cylinder engine - the inertia of the mechanisms affects it. To make it easier for you to navigate pressure units when choosing a suitable pressure gauge, we provide data on their comparative values: 1 kg/cm2 = 0.09806 MPa = 0.98067 bar = 14.2233 psi = 100,000 mm water column. = 735.561 mm Hg. = 0.96784 atm. As you can see, the units are easy to convert from one to another, not counting psi and millimeters of water/mercury - they are given in terms of “general information” and are practically not used in technology. If you have not set out to create a perfectly balanced motor, then almost all of these units can be reduced to a “common denominator” - they are practically equal. When choosing a pressure gauge, be guided by its operating range - the scale should exceed the maximum compression values, but at the same time be sufficiently “detailed” in order to compare compression values in different cylinders.

Online consultation

A compression meter belongs to the minimum set of tools that makes it possible to assess the technical condition of the engine and control system.

The compression gauge is a pressure gauge with a non-return valve and is designed to measure the maximum pressure in the cylinder at the end of the compression stroke (this value is often called compression). The measurement results are used to assess the condition of the parts of the cylinder-piston group and gas distribution mechanism.

It is important to evaluate not only the amount of compression, but also the rate of increase in pressure in the cylinder, as well as the difference in compression across the cylinders.

If the compression in the engine cylinders is lower than that set by the manufacturer, or the difference in compression between the cylinders exceeds the permissible level (usually more than 1 kg/cm), then it follows from this fact that repair of the engine cylinder-piston group is required, and the assessment of the technical condition of the EMS should be based on refuse at this stage.

Different models of compression meters differ in the amount of pressure measured (for gasoline and diesel engines), as well as in the number of adapters for connecting to different types of engines, depending on the shape and size of the spark plug hole.

The compression ratio is checked as follows. The engine with pre-checked and set valve clearances warms up to 80 - 90°C. The compression gauge sensor is screwed sequentially into the spark plug sockets (for “gasoline engines”) or into the injector holes (for “diesel engines”). Each installation of the sensor is accompanied by cranking the engine with the starter to 200-360 rpm. The maximum compression rate is recorded by the device. To reset the readings to “0,” the device has a special release button. An engine in which the difference in cylinder readings differs by no more than 1 kgf/cm2 (or 0.1 MPa) is considered to be in good working order. Diagnostics of a diesel engine is carried out in a similar way. For this purpose, a special compression gauge for diesel engines is used, equipped with an adapter sleeve. The measurement limit of such a device can reach 40 kgf/cm2 with a division price of 1 kgf/cm2.

There are also compressors that record measurement results on replaceable cards, which makes it possible to conduct a more accurate analysis of the state of the cylinder-piston group and gas distribution mechanism based on the nature of the pressure increase in the cylinder.

Do-it-yourself compression tester for diesel engines

Before you start making a compression gauge for a diesel engine with your own hands, you should consider a few points:

the pressure gauge must have a scale “with a margin” - its limit must be at least 50 kg/cm2;
the check valve (what it is needed for, we’ll say later) must maintain the pressure corresponding to normal compression.

What is a check valve for?

A check valve is necessary to record the compression meter readings, which are then reset by opening the valve.

The fact is that, in fact, a compression gauge is an ordinary pressure gauge that is capable of “holding” readings thanks to a check valve - otherwise, when the air injection stops or it is simply disconnected, the instrument needle will fall to “0”. The compression meter shows the maximum pressure pumped into the cylinder, and its readings are reset by pressing the check valve from the outside. However, you can measure the compression by calling someone for help who will turn the ignition key to start. Meanwhile, you can evaluate the compression, so to speak, “in real time” - by directly observing the device.

Making a compression gauge with your own hands

If recently the engine of your car worked like a clock - it started well, fuel and oil consumption was normal, there were no dips in traction - but then everything suddenly changed exactly the opposite, then one of the reasons for this deterioration may be a drop in compression — pressure developed in the cylinders.

A simple tool like a compression gauge will help you make sure that your assumptions are correct. A compression gauge is one of the types of pressure gauges; its feature is the presence of a check valve. This valve is installed so that when turning the crankshaft there is no release of pressure, that is, the compression meter will record the maximum pressure reading on the compression stroke.

How to measure compression?

We have already written about what compression and compression ratio are on our portal Vodi.su. This is one of the basic characteristics of the engine, and the octane number of gasoline depends on what pressure is achieved in the cylinders at the peak of the compression stroke.

It is clear that if compression drops, the fuel-air mixture does not burn out completely and fuel consumption increases.

Using a compression gauge is quite simple:

warm up the engine to operating temperature;
turn off the fuel supply (fuel pump), remove the terminal from the ignition coil (otherwise it may burn out);
remove all spark plugs.

This is the preparatory stage. Then it would be good if you have a partner who will press the gas pedal all the way to keep the throttle open. But first you need to install the compression tester hose into the spark plug wells - the hose comes with several types of nozzles that fit the sizes and threads of different types of spark plugs - Euro plugs or regular ones.

Then you will need to turn the crankshaft with the starter so that it makes several revolutions. Two or three seconds is enough. Record the indicators and compare them with the data from the table.

You may also need a motor oil syringe. By pouring a little oil into the cylinder, you will understand why the compression is reduced - due to wear on the piston rings (after injecting the oil, the compression level will return to normal), or due to problems with the valves, timing mechanism or cylinder head (after injecting the oil the level will still be lower than necessary).

As you can see, nothing complicated. But there is one problem - there are budget compression meters on sale that do not give accurate readings; the error can be very large, which is not acceptable for accurate measurements.

Good devices are expensive - about a hundred dollars. And some drivers generally prefer not to bother themselves with such questions and go to a service station in order to pay a few hundred rubles for such a simple operation.

Making a compression gauge with your own hands

Assembling this measuring device turns out to be not so difficult; all the necessary elements can be found in the garage of experienced car enthusiasts or at auto parts markets.

What you will need:

pressure gauge;
valve from the camera for a truck (popularly called a “nipple”);
spool (nipple);
brass adapters of the required diameter and thread;
hose (high pressure hydraulic hose).

Do-it-yourself compression tester for gasoline engines

It is easier to make such a device than for a diesel engine - you can use a spool from a truck tire as a check valve. In this case, you can use the entire valve in a brass body - it can be easily soldered to a pre-selected brass nut using ordinary tin solder. You can make a compression gauge with your own hands from a spark plug , using the latter as an adapter. It is enough to simply remove the ceramic insulator by simply breaking it with a hammer. The internal electrode and insulator, as a rule, can then be easily removed through the “top” of the spark plug. You can do it even simpler - put a piece of rubber hose on a metal tube of a suitable diameter and give it a conical shape by sanding it. However, in order to measure the compression, you will have to call an assistant - you will need to hold the hose with your hand. This simplified method is not suitable for a diesel engine - the pressure is very high, and you cannot press the seal properly with your hand.

Compression gauge - do it yourself - DRIVE2

Greetings to all subscribers and just readers! This time I would like to present to your attention a device that is useful in garage use - a compression meter, which I assembled from scrap materials. Of course, it would have been easier to buy a ready-made one, but I wanted to make it myself, because it’s more interesting. I hope there is no need to explain why and how this device is used, so I’ll go straight to the description of its manufacture. And, to begin with, I will show you what served me as parts, parts and blanks for a homemade compression gauge.

Full size

This photo shows: - a used Soviet pressure gauge, 16 kgf/cm², with a rear fitting, accuracy class 4%; — used clutch slave cylinder hose from VAZ-2101-07;

— a fitting from an old car camera. — a filling valve from some old Soviet gas lighter; The valve from the lighter will be located in the tip of the compression gauge, which is screwed into the spark plug hole of the engine. The purpose of this valve is to allow air inside the compression gauge and to prevent air from escaping back into the engine cylinder. A hose will be attached to the tip, the other end of which will be connected to the pressure gauge through a special coupling. A pressure relief valve will be embedded into the wall of this coupling (a button that is found on every compression gauge; it is used to bleed air after measurement). The same valve from the chamber with a spool will serve as this valve. I turned the mentioned tip and coupling on a lathe, or rather, a lathe was needed mainly to make the tip (I had previously thought about using the metal part of the spark plug as a basis, but found this option to be of little use). The blanks for the parts were this found steel contraption and a piece of a brass 17-mm hexagon:

Full size

From the sketches below, you can understand what exactly was planned to be obtained from these blanks:

The following pictures show some stages of the manufacturing process.

www.drive2.ru

How to measure compression

To measure compression yourself, first charge the battery and warm up the engine to operating temperature.

First of all, you need to ensure the proper speed of rotation of the crankshaft - you will have to turn the latter with the starter. True, to get a more complete picture of the engine’s condition, you need to rotate the crankshaft at different speeds - the compression values directly depend on the compression dynamics. But this method is acceptable only for large specialized car services equipped with special stands, and it can only be used by dismantling the unit. For independent measurements, first, properly charge the battery and warm up the engine to operating temperature. Regardless of whether the engine is gasoline or diesel, check the cylinders one by one, having first turned off the fuel supply to the injectors (you can simply disconnect the injector power connector block). There is no need to crank the engine with the starter for a long time - 3 to 5 seconds is enough. If the results are disappointing, pour about 30 grams of engine oil into the cylinder (or cylinders). If after this the compression rises, then there is a malfunction of the connecting rod and piston group. That is, wear (breakage) of piston rings, wear of the cylinder, etc. If, after filling the oil, the compression indicators have not changed, then look for the reason for poor engine performance in the cylinder head - it could be a burnt-out valve (as well as its seat), a broken valve spring, cracks in the cylinder head, etc.

In conclusion, not all faults can still be identified using a compression meter. Before you start making a compression gauge with your own hands, for example, for a diesel engine, keep in mind that modern injection systems for diesel engines (for example, Common Rail) provide for pumping fuel pressure into a common rail and controlling the combustion process of the mixture. Unfortunately, such systems are very demanding on fuel quality, and often a modern diesel engine can baffle even an experienced technician. There are known cases when a carefully repaired engine with excellent compression refused to start only because its owner did not sufficiently monitor the cleanliness of the fuel system.

How to measure engine compression

One of the reasons for a decrease in car power is a decrease in engine compression. We'll tell you how to check it with or without a compression meter. What is an engine oil check?

Without compression meter

There are two ways to measure compression: precise measurement - with a compression meter and approximate - manually.
The last method of measurement requires a certain skill, but at the same time there is nothing complicated in it. Remove all spark plugs except the first cylinder. You will need to remove the car wheel and prepare the key. Next, manually turn the engine crankshaft until the compression stroke ends in the first cylinder (this can be determined by the coincidence of the marks). Then screw the spark plugs into the other cylinders one by one and also turn the crankshaft. You can understand which cylinder has low compression by comparing the forces applied to rotate the crankshaft. This is a rather arbitrary measurement, because... it is associated with the subjective characteristics of human physiology. Therefore, it is preferable to use a compression meter. You can find out the required compression value for your car from the technical documentation.

Using a compression gauge

Start the car and warm it up to operating temperature.
Remove the spark plugs.
Ask for help, because... A prerequisite for measurement is to fully open the throttle, and the assistant will turn on the starter by pressing the gas pedal all the way.
Insert the tip of the compression gauge tightly into the hole of the spark plug, make sure that the connection is secure.
Turn on the starter and crank the engine until the pressure gauge readings stop increasing (usually 2-3 seconds). The test is performed only with a fully charged battery.
Turn off the starter and read the instrument readings. The measurement is carried out in all cylinders.
Do not forget to remove air from the compression gauge after each measurement. If you get data that differs from the norm, repeat the measurements on this cylinder.

The difference in compression gauge readings between cylinders should not exceed 10% of the maximum reading.
Thus, a 15% drop in compression in a given cylinder indicates wear on the piston, piston rings or valves. Prolonged operation of the engine with such indicators leads to increased wear and possible engine repair. You can view the table of measurement results HERE.

What to do if you don't know the regulatory data? The approximate compression ratio for a car engine can be calculated using the formula:

Compression (kgf/cm2) = compression ratio * X coefficient

The compression ratio is always recorded in the technical specifications of the engine. The X coefficient depends on the type of engine:

X = 1.2-1.3 for gasoline engines;

X = 1.7-2 for diesel engines.

Compression in new cars or those in good condition should correspond to the manufacturer's data or the data resulting from the above formula.

Oil check

The loss of compression depends on the condition of the engine parts and, in particular, on the wear of the piston rings.
There is one way to check the technical condition of the rings. Let's call this option "oil check". For this type of fault determination, we need the syringe and machine oil previously mentioned in the tools. Inject 10-30 ml of engine oil into those cylinders where compression is low. Close the spark plug hole, rotate the crankshaft a few times to distribute the oil throughout the cylinder, and then measure the pressure in the engine again.

Now you need to compare the compression meter readings before and after.

If the compression has increased significantly or is close to normal, it means that the piston rings are leaking due to wear or there are scoring marks on the walls.
If the compression increases slightly, the valves and piston rings are leaking or the engine head gasket is damaged.
If the readings remain unchanged, then the valves are leaking. Valve grinding required.

If the compression readings are not too critical, then I recommend using engine additives. After a certain time (at least a week), repeat the measurements. If the indicators have improved, then you can continue driving. If they remain the same or worsen, prepare for an early engine repair.