When you buy a car with a diesel engine. Used diesel: how to check before buying. Diagnostics of engine condition using spark plugs

Diesel engines appeared quite a long time ago, and they got their name in honor of the creator. But they began to be used in the automotive industry just a couple of decades ago. It's all about too much weight. To create a properly functioning device, it was necessary to use heavy parts. Over time, technology has improved. And today you can buy a car with a diesel engine, which will work quite acceptable.

When the engine fails, further operation of the vehicle is prohibited. The main technical unit is deteriorating, so you simply won’t be able to drive. And in most cases, it is irrational to repair such expensive parts as injectors or exhaust systems. It’s easier to buy a new unit to restore the car’s functionality.

Mass segment

Ford Focus. The diesel option is not cheap, but a good alternative to the petrol one - 115 horses, 1.8 liters. Fuel consumption is low - 7 liters.
Ford Fiesta. Assembled in Germany, which is why the build quality is a solid five. The engine is no different in power - 75 horsepower, but consumption is a little more than 4 liters per hundred.
Volkswagen Golf. It is invariably popular in the secondary market - it is assembled with high quality and will last for centuries. A good option is a 2-liter engine with a consumption of some 6.5 liters per 100 kilometers.
Renault Logan In diesel version, it has a 1.5-liter engine producing 85 hp. Consumption in the city is about 6 liters per hundred. The motor is reliable and durable.

Skoda Octavia Combi. A station wagon with a spacious interior, a large trunk and a two-liter engine. Average consumption is 7.5 liters.
Skoda Roomster. Small engine - only 1.2 liters with 75 horsepower. But reliable.
Peugeot 408. Engine capacity in the diesel version is 1.6 liters, power is 112 horses, consumption is only 5 liters per hundred. High quality iron.
Hyundai i30. 2 diesel engine options - 1.4 and 1.6 liters, 90 hp. Build quality is top five.
Kia Pro Cee'd. A 1.6-liter engine with unprecedented consumption - a little more than 3 liters of fuel per 100 km.

Diesel fuel classification

To classify diesel fuel, two indicators are traditionally taken into account: the degree of sulfur content and the maximum cloud point. This is a standard adopted by the state, corresponding to the European system and specification EN 590. For the purposes of this article, temperature indicators are of greatest importance.

“Temperature” classification divides fuel into grades and classes, which are indicators of the lowest temperature at which the fuel can pass through the filter.

The maximum filterability temperature (t°C) is indicated in parentheses.

For areas with temperate climates, fuel grades are determined	Fuel classes are determined for cold climate areas
A (+5); B(0); C (-5); D (-10); E (-15); F (-20).	Zero (-20); first (-26); second (-32); third (-28); fourth (-44).

Depending on temperature indicators, diesel fuel is divided into three main types and one additional (last).

Summer diesel fuel. Remains liquid down to -5 °C. Recommended for use at temperatures above 0 (filterability t °C is not determined).
Winter diesel fuel. It should not thicken to temperatures below 35 degrees. Use in frosty conditions (-20 °C).
Arctic diesel fuel. Recommended for severe frosts from -45 degrees (-38 °C).
Interseasonal diesel fuel (-15 °C).

For each of the three main types, its own standards for density and viscosity indicators are determined. It is these characteristics that determine the efficiency of the engine and when and what fuel to use. They are also often used to determine the quality of diesel fuel.

The viscosity standards are as follows:

summer type - 3.8/6.0 cSt;
winter type - 1.8/5.0 cSt;
Arctic type - 1.5/4.0 cSt.

Density indicators will be discussed further.

Elite class

Porsche Cayenne. Its dynamics and consumption ratio is amazing - with an engine producing 382 horsepower, the car consumes only 10 liters per hundred.
Volkswagen Phaeton. The model is outdated, gluttonous - it consumes 20 liters per hundred in mixed mode. But the car will be appreciated by lovers of comfort and luxury - natural wood, exclusive leather, eight airbags and much more.
BMW 550MD. Equipped with a 3-liter turbodiesel engine with a power of 381 hp. Also of note is an improved ignition, intake and exhaust system.

You can also look at other cars if, for example, you are a fan of a certain brand. But keep in mind: the more expensive the model you are interested in, the more its repair will hit your wallet.

How to choose a used diesel car

When you have found suitable options, the most crucial moment comes - you need to examine them and make a choice. Be patient - you will have to do a whole set of steps. But they won’t give you a “bucket” this way. So, how do we choose a diesel car:

We start the cold car. The startup happens “on a click” and the car hums like a tractor - everything is in order with it. If the engine starts slowly, the pistons are faulty. You will have to fork out a lot of money to replace them.
We wait 5-10 minutes, then turn off the car and start it again. A warm car should start a little slower than a cold one.
We press the accelerator (it is located under the gas pedal) all the way. There is smoke coming from the exhaust pipe - the pistons will soon “cover”. White smoke indicates water or other liquid has entered the fuel.
Let's listen to the engine. The engine should not knock or grind after it warms up.
We examine the engine compartment. We see new parts, traces of sealant, dents - the car may have been in an accident. Using such a machine can become an unaffordable luxury.

If the car does not pass the inspection on at least one of the points, refuse it or ask the seller for a good discount.

This must be done before buying a used diesel car.

Be sure to check a used car with a diesel engine for legal purity, find out how many owners it has had, what the actual mileage is, and whether there are any outstanding fines. This and much more is possible. Download the application to your smartphone and check the car directly at a meeting with the seller. You will receive a full report about the car you are interested in in 5 minutes - you only need to know the car’s license plate number or VIN. In addition, the service can check Japanese cars.

Before purchasing, find out as much as possible about the car you are interested in. Then, long before the purchase, you will be able to understand that this is a pig in a poke. After all, our compatriots often squeeze every last drop out of diesel cars before selling them.

Recently, diesel engines have gained wide popularity. They are installed in many cars, including compact city cars, huge SUVs and even sports cars. This is due to low fuel consumption.

Since diesel is ubiquitous, the aftermarket is flooded with such vehicles. And all potential car owners need to familiarize themselves with the rules for checking such cars before purchasing.

Which diesel is better to choose?

Initially, all potential motorists need to decide what exactly they want to get from their future car. Some give their preference to power, others to reliability and safety, and still others to low fuel consumption. It is the engines that are responsible for all these characteristics, and the other systems and mechanisms of the technical part play secondary roles.

When choosing an engine, you need to consider:

Small engines consume the least fuel;
Large engines are more reliable and durable in operation;
The presence of a turbine increases power characteristics;
The absence of a turbine simplifies the engine design, which has a positive effect on reliability and durability.

Taking into account the above points, you can approximately determine what engine size is suitable for you. However, for beginners, the data does not mean anything; they will need to choose the first vehicle based on luck. They will be able to determine which engine suits them only through practice, which was temporarily not enough.

How to check?

Once you have decided on the engine size, you will need to check it. You should not buy a diesel car without checking it, since the car can start and drive normally, even if there are problems.

Checks include the following steps:

Visual inspection. Any contamination is considered normal. During a visual inspection, you should only be interested in oil leaks. If any are present, it is recommended to refuse the purchase in favor of another option. Otherwise, you will soon have to go to a car workshop for repairs, or even completely change the engine.
Remove the pipe near the air filter. Its contamination indicates various problems. Minimal – air filter contamination. This problem can be solved by simply replacing the filter or cleaning it. However, the presence of dirt may also indicate problems with the cylinder-piston system. If it wears out badly, there is no point in repairing the engine; it is easier to buy a new unit.
Start the engine, the car should be in working condition in a couple of minutes, this is enough to warm up the engine. If the engine is not started immediately, but after several revolutions of the crankshaft, then there are hidden defects. Try starting the car at different intervals several times. Every time the car must respond quickly to the turn of the key.

You should be alerted to abnormal exhaust gases. Light blackness is acceptable, however, all other shades of the exhaust indicate probable problems in its subsequent operation.

Also, pay attention to the characteristic tapping sounds. These appear if the engine is deformed, or some of its parts are not securely fastened, or the fastenings are loose.

Please note that at sub-zero temperatures the engine will take longer to warm up. Therefore, it is not recommended to buy a car in winter, since it is not possible to properly check it for proper operation.

The decision to buy a car with a diesel engine suggests the reasons why this option is chosen. The reasons determine the extent and main parameters of checking the engine before purchase. But the question of how to check a diesel engine when purchasing is the main one.

Pull out the engine oil dipstick and determine the oil level and condition

If the oil is very clean and transparent

, then it was definitely changed recently. Here it’s worth asking why they did this if the car was going to be sold? Probably not in order to protect you from unnecessary expenses on changing the oil. If the oil has darkened a little, this does not mean that the engine is in poor condition - this is quite normal, unless, of course, the oil is completely black.

If the oil shows signs of foaming and its color is milky

, somewhat whitish tint, then most likely coolant has got into the oil, for example, due to damage to the cylinder head gasket, and, in this case, it is better to refuse to purchase such a car.

Check the coolant level and also pay attention to whether there are any traces of rust in the cooling system expansion tank.

If such traces are found, and even more so if the coolant itself is rusty in color, then most likely the engine has overheated, which is a very dangerous sign.

If an external inspection of the engine does not reveal any problems, then ask the car seller to start the engine, and at this time watch and listen to how it starts, and what color the exhaust gases are at the time of start-up.

Diesel engine selection

Before coming to the dealership, you need to understand the basic characteristics that the engine of the car you are buying would have. There are no universal diesel engines, so desires must be linked together.

An engine cannot be powerful and not actively consume oil, reliable and relatively cheap to maintain.

Powerful motors have a long service life and are reliable, but are not as economical as low-power engines, which are less reliable and have a shorter service life.

Engines without turbines are more reliable, but turbocharged diesel engines have better power characteristics with lower efficiency.

Having chosen an engine that suits the buyer in terms of its performance, you should understand the methodology for testing a diesel engine. The engine ultimately determines the fate of the car you buy.

Methodology for checking diesel engines during the car buying process

Having previously chosen a car with a diesel engine that suits your desires, you should begin to study the engine.

When purchasing a new car, the inspection method is simpler and consists of parts of the general method for a used car.

It is better to break the check down into steps.

At this step, it is necessary to inspect the diesel engine for the presence of fluid leaks characteristic of engine overheating. It is better if there are no drips on the seals and other inspected places.
It is necessary to remove the pipe that connects the air filter to the intake manifold, and if the diesel engine is turbocharged, then to the turbine. If traces of oil are found in the pipe, then wear is possible, which may be significant in the cylinder-piston group or, at best, the air filter is very dirty.
The diesel engine should be started, and if it does not start the first time, then there may be a hidden defect. Repeat starting the engine at different intervals without touching the gas pedal:
A quiet knocking sound when the diesel engine is running is acceptable, other sounds should be acceptable.
At idle, you need to increase the speed to 3000-4000 per minute, twitching and vibration are not acceptable. The color of the exhaust should not be bluish, otherwise the ignition will be delayed or other inaccuracies in the unit settings.
If you accelerate sharply at idle and at high speeds there is a bluish exhaust and vibration, then in these modes there will be a loss of power.
If the exhaust is black and the engine is knocking, then you should not be interested in such a car any further.

Method for determining fuel density according to GOST

Traditionally, to determine the density of fuel, a special device is used - a hydrometer. This is often a glass tube with a density scale. There are different hydrometers for different types of fuel. In the case of diesel fuel, devices such as AN, ANT-1 and -2 (for petroleum products) are used.

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The device is immersed in the liquid and the indicators are measured: the density of the fuel is the ratio of the mass of the device to the volume it occupies in the liquid.

Based on the results of measurements, the fuel is assigned to one of the types corresponding to GOST:

summer diesel fuel - density 860 kg/cubic meter;
winter diesel fuel - 840 kg/cubic meter;
Arctic diesel fuel - 830 kg/cubic meter.

Since the density of the fuel depends on temperature, all measurements are made at +20 ˚С.

If we take into account the variability of the environment, then with a change in temperature by 1 °C, the density of diesel fuel will also change - by approximately 0.00075. This coefficient makes it possible to calculate the density of a liquid under different temperature conditions. However, this only applies to the pure product.

Fuel does not always have the declared characteristics. Often, a low-quality product contains impurities of unknown origin. Therefore, it is recommended to refuel at proven gas stations, where the quality of the fuel is guaranteed and the risks of getting summer fuel instead of winter or Arctic fuel are minimal.

If there are doubts about the density of diesel fuel, measurements can be carried out independently.

Checking engine compression and other parameters

Sometimes, in addition to the method presented above, it is desirable to check some engine parameters using express methods that do not claim absolute accuracy. Sometimes these methods produce useful results.

It is advisable to check engine compression with a special device. For a diesel engine, the permissible value is 36 atmospheres, a minimum of 31 and the pressure spread across the cylinders is within two atmospheres.

If there is no device, then it is possible to evaluate the compression, at least by eye. You need to turn on the engine, carefully remove the diesel filler cap and simply place it on the neck. If the gases push the lid back, the compression is probably not normal. High-quality diagnostics are carried out only by specialists at service stations.

If you start the engine, the radiator is filled with antifreeze according to the norm, wait until the thermostat opens and watch whether or not air bubbles come out into the neck of the radiator with the engine running. The appearance of bubbles indicates damage to the cylinder block.

The condition of some diesel units can be approximately assessed by inspecting a running engine in a car.

To determine the condition of the piston system, it is necessary to sharply increase the speed to 3000 for 5 seconds on a heated unit; if the exhaust pipe does not smoke, then sharply increase the speed to 4200 and hold for 3 seconds. If there is no smoke, the piston system and turbine are operating normally.

But if there is smoke, there will be increased oil consumption. The more black smoke, the less traction performance.

Checking the injection pump pump comes down to determining the ability to start a warm engine; if it starts with voltage, then the pump is faulty.

An engine tested by the above methods should be considered conditionally tested; a thorough check is possible only in a service organization.

To the question of how to check a diesel engine when buying a car with maximum completeness, the answer is simple - you need to contact a service center.

Motor operation

The health of the engine is largely determined by the absence of the following symptoms:

increased vibrations;
, metallic ringing sounds.

You definitely need to look beyond. Blue smoke is especially dangerous, as it indicates that the oil has burned out. In the best case, you will get away with replacing the valve stem seals; in the worst case, a major overhaul of the engine is inevitable. If you start a cold diesel engine with mileage, a small amount of gray smoke is acceptable. After a few minutes of operation it should disappear. There should be no black smoke at idle. If the car has a particulate filter removed, then light smoke may appear when the gas is sharply pressed to the floor. With the engine running, carefully open the oil filler neck. If you see smoke, it means the valves are not sealing. Exhaust gases break into the cylinder head cavity. Also, at idle, pull out the dipstick. The presence of smoke will indicate a poor condition of the CPG or clogged crankcase ventilation.

After the engine reaches operating temperature, open the expansion tank cap. Just be very careful, as there is a chance of getting burned by hot antifreeze. Ask the owner to raise the engine speed to 4-5 thousand several times. No air should come out of the pipes. The opposite will indicate a breakdown of the cylinder head gasket or a crack in the block. Also, there should be no oily deposits inside the coolant tank under any circumstances.

Test Drive

The condition of the engine directly affects the dynamic performance of the car. Try driving in all engine operating modes (low, medium, high speed). When you press the gas sharply there should be an appropriate response. If the speed fluctuates, or the engine “stalls” and accelerates sharply when desired, financial investments will be required.

Diagnostics

The best way to check the condition of the car’s “heart” is to conduct computer diagnostics. You can carry out diagnostics yourself using an OBD-II adapter and the appropriate software. Unfortunately, a universal kit rarely provides useful information, so it is better to contact specialists with specialized equipment. Especially when it comes to choosing an expensive modern car.

Since it is very difficult to check the engine when buying a premium car yourself, contact a dealership. There they can measure your compression and also inspect the cylinders with an endoscope for scoring.

What does the cost depend on?

The cost of a diesel engine is an important characteristic. This is what is most interesting to buyers. You can analyze prices on the website ZAPCHASTI.RIA.COM, since the maximum number of advertisements for the sale of power units is collected here. This way you can find the best deal.

The price depends on many factors, but the most important ones are:

New or used. New power units are purchased extremely rarely, mainly for expensive cars. When an engine fails on the average vehicle, motorists are better off taking advantage of aftermarket offerings. Otherwise, the costs will be too irrational.
Car make and model. They have significant structural differences; in some places there are units with a simple and accessible design, and in others with a complex one.
Brand popularity. Many companies that have earned a positive reputation and have been presenting their products on the market for a long time, mark up the cost of their name. But, despite the high prices, such products also have their advantages. For example, you are guaranteed to receive a high-quality product, since the manufacturer will not risk its reputation. However, this does not mean that it is impossible to find simple models on the market that are manufactured by unknown companies and are of high quality.
Technical characteristics of diesel engines. The design of a diesel engine has many advantages. But its main drawback is too much weight. Therefore, it is difficult to create a powerful vehicle based on a diesel power unit. Accordingly, the lighter the engine, the more expensive it will cost.

Other factors also influence price categories. Please note that if you use the website ZAPCHASTI.RIA.COM, you can find excellent options and bargain on the secondary market. The ability to bargain plays an important role in determining the amount that you will ultimately have to pay.

How does density level affect fuel consumption?

The density of a fuel is far from just its freezing limit. The amount of energy released by diesel fuel also depends on its density.

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The denser the fuel, the more energy is released during its combustion. Accordingly, the higher the density, the more efficient the engine efficiency will be. Therefore, high-density fuel is the most economical option. But there is a nuance.

The fact is that the temperature and density of diesel fuel are closely related to such a phenomenon as viscosity. Fuel with a lower density has lower viscosity. Accordingly, it is more liquid. And therefore less susceptible to crystallization.

At the same time, the degree of density is not constant and largely depends on temperature. For example, an increase in the temperature of diesel fuel reduces its density.

Let's summarize:

the denser the fuel, the more economically it is consumed;
more liquid fuel crystallizes less;
heating the fuel reduces its density.

All this affects which fuel to choose depending on the season.

How to check before buying?

To buy a diesel engine that will work and have a good residual life, you need to pay attention to several important points when checking:

Visually assess the condition of the unit. If there are obvious damages, dents or other defects, you should immediately refuse the transaction. It is also recommended to check for oil leaks where they should not be. However, traces of oil sweating on individual structural parts are allowed; after all, you are not buying a new motor;
Remove the pipe from the intake manifold. A small amount of oil is allowed on it. This indicates that the engine is in good condition and was used for its intended purpose. But if there is too much oil inside, then the situation is critical. At best, you will have to eliminate severe contamination of the filter and the consequences of this trouble. But there is a possibility that the cylinder-piston group is damaged;
Start the engine. If it is warmed up, it should start literally half a turn. It is recommended to perform the procedure several times, each time leaving the motor at rest for different periods of time. If this does not happen, then the power unit has certain hidden defects, which can only be identified at a service station using computer diagnostics;
After starting the engine, wait a little, but then increase the number of revolutions to 3-4 thousand. In this case, the motor should not begin to vibrate, but remain in its normal position.

It is also recommended, whenever possible, to check how the engine behaves in winter. Perhaps it will consume too much fuel to warm up, or operate at an unstable speed. However, if you purchase equipment in the warm season, as usually happens, you will not be able to predict the behavior of the unit in winter unless you go for a thorough diagnosis at a service station.

How to check a diesel engine without precise knowledge of “mechanics”?

Starting after a long stay.

Why is this so important? Every diesel engine uses a high compression ratio in the cylinder to ignite the fuel mixture. During normal operation, oil fills the space between the piston and the cylinder walls helping to maintain normal pressure. Oil after idle time (1-2 hours) flows into the oil sump. In order for it to reach the cylinder walls in sufficient quantities, the engine must run for a minute or longer.

Therefore, cold starting is the most difficult operating condition for a diesel engine.

The best time to buy a car with a diesel engine is winter. If the engine starts easily, then there are no problems with compression in the cylinders, as well as with the operation of the cold start system (the injection timing is specially shifted at low temperatures for better cold starts).

Test run

Even if a diesel engine works well in a parking lot, do not refuse the opportunity to take it for a test drive. Only under load will the technical condition of the engine emerge.

It is worth paying attention to:
the acceleration method, the increase in power after turning on the turbocharging, the level of noise and vibration.
It is better to carry out a test drive in urban conditions.

The main focus here is on smooth starting and the presence of extraneous knocking from the transmission when the load changes (add and release gas). The culprit for the knock could be the dual-mass flywheel.

- an expensive element of the car. It is worth observing the behavior of the engine when it is turned off. A metallic sound when the engine stops is another sign of a flywheel strength problem.

Check the turbine

A new turbocharger usually costs between 300 and 800 euros (

the price depends on the manufacturer, model, type of turbine
)
. So it’s better not to buy a car with a problem unit. First of all, suspicion should be caused by intense oil leaks from the intake system. A working turbine should not be too loud. Often, a drop in power can be caused by a malfunction of the turbine control system.

Inspecting the diesel engine for oil and coolant leaks

We inspect the engine for leaks, oil stains, etc. Please note that a freshly washed engine is suspicious. Perhaps the seller wants to hide something just before the transaction. The presence of drips, especially on the oil seals, may indicate possible overheating of the engine in the past.

Remove the coolant expansion tank cap and examine what's inside. Any grease stains on the surface of the liquid, or traces that look like butter, are suspicious. This could mean a faulty gasket or microcracks under the head.

Remove the oil filler cap. If the oil feels thick or sticks to the touch ( WARNING!!!

), this may mean that it is artificially compacted.
Any additives in oil are a suspicious signal.

Observe the display while starting the engine

We look when the oil pressure light goes out. A second or two is an acceptable time interval. Longer than this interval is a bad sign; the indicator goes out too quickly, also bad. In both cases, the cause may be a worn motor (sealing with oil additives) or a trick in the power supply circuit.

Air filter.

We look at the air filter ( should be dry or moderately contaminated with oil

). Remove the pipe connecting the filter to the intake manifold or to the turbine (variation of the engine with a turbine). Traces of oil in the pipe will indicate severe contamination of the air filter or wear of the cylinder-piston group.

Check the presence of a diesel particulate filter.

Theoretically, after
150-200 thousand km, the filter becomes clogged
.
Soot is the first signal that something is wrong.
How can we recognize the presence of a particulate filter in the car we want to buy?

The first thing you need to check is the exhaust pipe tip. It is enough to stick your finger into it (of course, this should be done on a “cold” engine). If we find a thick layer of soot in the pipe, this is a sign that the filter is mechanically damaged or is missing.

You can also check for the original seams in

places where the particulate filter is installed.

A working filter removes 97% of soot and particulate matter.

Points to start the engine

Try starting the engine several times with the engine already warm ( without pressing the accelerator pedal, without warming up the glow plug

) with different start intervals. If you can’t start it right away, as they say “half-turn,” then this behavior may indicate the presence of a hidden defect.

At idle speed of a warm engine, exhaust emissions should not be accompanied by smoke. An exception may be a slight emission of smoke during startup. The engine should run clean and smooth.
Raise the speed slowly, up to 3-4 thousand according to the tachometer. The motor should NOT EXPERIENCE VIBRATIONS.
The appearance of bluish smoke will indicate to you either an incorrect ignition installation (later) or other malfunctions.
If you sharply increase the speed of the gas pedal, a noticeable vibration appears, bluish smoke is emitted from the exhaust - the engine experiences a significant loss of power.
Remove the oil dipstick and gradually add gas. A vigorous plume of smoke coming from the hole indicates a potential lack of compression in the engine. Insert the dipstick back and unscrew the oil filler plug. If, when adding gas, a column of smoke flies out of the hole, the engine needs major repairs ( significant wear of the piston group
). An inconspicuous, steam-like, slight release of smoke (or hot air) released from the neck opening is acceptable.

Particular attention to the injection system.

Repairing a worn injection system can cost more than 15-20 thousand hryvnia!
An accurate diagnosis can only be made after testing at a special stand. Fortunately, the symptoms of a worn injection system are easy to spot: loss of power, engine vibration, and black exhaust.
Order an electronics test.

Before purchasing, it is worth spending from 50 to 100 grams on computer diagnostics to obtain additional information about the condition of the engine. During such a study, the mechanic can check, for example, the degree of filling of the particulate filter, and what errors have occurred in the engine recently.

Our advice.

The ideal option is
to entrust the inspection to an expert.
In this case, the cost of professional inspection of the car will be most justified.

If you need a car not so much to drive it, but as an exciting hobby that involves tirelessly fine-tuning the car to working condition, then you can easily focus solely on the price criterion.

However, in most cases, a car is chosen precisely as a means of transportation, and at the same time it is a reliable means that does not require additional significant financial and time investments.

To ensure that your new purchase does not disappoint you later, it is important to avoid all the “pitfalls” - hidden defects inherent in a particular car that interests you in the car market.

Otherwise, instead of taking full advantage of the advantages of a diesel engine, you will get an unpleasant set of its disadvantages - everything that faulty, worn-out diesel engines suffer from - poor starting, increased smoke, increased fuel consumption.

The first thing you need to do - even before going to the car market - is to clearly determine which engine characteristics are most important to you

. Unfortunately, most power units cannot simultaneously be powerful, reliable, economical, and have good maintainability... Unfortunately, compromises will have to be made.

Small engines (installed in small cars) generally have good fuel efficiency, but at the same time they are less reliable, less durable and have more modest power characteristics in comparison with their “bigger brothers”.

The large working volume of the power unit, as evidenced by statistical calculations, provides it with a greater level of reliability.

Non-turbocharged engines, in comparison with turbocharged designs, are more reliable, durable and at the same time have better fuel economy indicators.

Engines supplemented with a turbine, in turn, although less reliable and distinguished by a special “appetite,” are best suited for those who put power performance first.

First, we inspect the idle engine.

- for the presence (preferably, of course, absence) of oil drips, traces of coolant release, indicating that the engine was overheating.

Traces of oil sweating on the engine may be present (to a slight extent). It is highly desirable that they are completely absent from the seals.

We remove the pipe that connects the air filter and the intake manifold (in turbocharged models - the air filter and the turbine). The presence of a large amount of oil in the pipe, at best, indicates a serious degree of contamination of the air filter or crankcase gas exhaust system; at worst, it is a consequence of severe wear of the cylinder-piston group.

Let's start the engine.

If it does not start “hot” with a half-turn, then this should be taken as evidence of some hidden defect. The check must be performed several times, with different intervals between runs. In this case, you do not need to press the gas pedal and warm up the spark plugs - there is no need for this. If the seller insists on such actions, then he is deliberately trying to hide from you the presence of a defect in the power unit.

Pay attention to the exhaust

when starting the engine. There should be no smoke at idle speed on a hot engine. Only a small amount of smoke is allowed during startup.

Slight knocking in the motor

(“rolling pebbles”) is the norm for diesel engines, but knocking noises that stand out from the general rhythm should alert you, especially if they persist as the speed increases.

Smoothly increase the speed.

From idle we gradually move to a value of three and a half - four thousand revolutions per minute, watching the engine - it should not twitch or shake.

We perform the same operation again, assessing the color of the exhaust

. If ragged blue smoke appears as the speed increases, this indicates either late ignition or other defects in the engine.

Press the gas pedal sharply

and again we observe the engine and exhaust. If the power unit shakes and ragged blue smoke comes out of the exhaust pipe, then at the speeds at which this happens, there will be a significant loss of power.

If there are knocking noises or black smoke is pouring out of the exhaust pipe, it is better to cross such a car off your list.

If everything is in order, we continue the inspection. Compression in the engine must be checked at a service center

(acceptable value - 36 atmospheres, acceptable - no less than 31, spread of values across cylinders - no more than two atmospheres). However, it can be previously assessed on site. Carefully unscrew the oil filler cap with the engine idling. If after this, when you try to put the lid on the hole, it is thrown away by the gas flow - this is definitely a bad sign.

However, if this does not happen, this does not guarantee the absence of problems with compression. Diagnostics must be carried out at a service station - in addition, oil pressure

in the oil line on a hot engine at idle speed. (An acceptable value is at least one atmosphere, for turbocharged power units - at least one and a half atmospheres. Readings are taken using a mechanical pressure gauge).

Let the engine cool down (at least to 50? C), open the radiator cap, add coolant to the top, and close it. Then you need to start the engine, and after the thermostat opens, look (with the engine running) to see if air bubbles are coming out of the radiator

. If this occurs, then either the block head, the gasket, or the block itself is leaking.

Checking the start of the power unit “cold”

This means, ideally, that it is started at the temperature at which it will be operated in the winter (thus, in the summer it will not be possible to identify all possible defects using this method, but still it should not be neglected in the warm season).

If the engine starts as quickly as when it was hot, then everything is fine both with compression and with the operation of the cold start system, glow plugs, battery, and starter.

At idle speed, the power unit should operate without interruption. It is allowed to operate somewhat more harshly in “cold” mode - the reason could be the special cold start systems that some fuel injection pumps are equipped with (they “deliberately” shift the advance angle of diesel fuel injection at low temperatures in order to improve engine starting).

Naturally, without testing the engine in real road conditions

not enough. Only by recreating in practice all possible operating modes of the power unit will it be possible to understand how serviceable it is.

Tests in extreme conditions, of course, should continue for a few seconds - this will be enough to “diagnose” possible problems, and will not lead to their creation.

In order to check the serviceability of the fuel injection pump regulator

, you need to sharply press and release the gas pedal. If the engine quickly returns to idle, everything is fine. If it is slow and blue smoke continues to come out of the exhaust pipe in the lower speed mode, the turbine or engine is faulty. If there is no smoke, but the power unit returns to idle slowly, the injection pump regulator is faulty.

If there are no extraneous knocking noises in the engine, heating exceeding the norm, significant smoking, or a drop in power in certain driving modes, this is a good sign.