We choose a diesel car. Before you buy a diesel - think about How to choose a diesel car with mileage

01.10.2019

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Diagnostics of a modern diesel engine as a whole and its individual systems usually takes much more time than in the case of gasoline units. To determine the malfunction, a combination of professional equipment and high qualification of the master is necessary. But even in the presence of such a base, one has to resort to specific diagnostic methods.

The main difficulty in diagnosing is that it has fewer system parameters, the evaluation of which allows you to immediately find a malfunction. One of these parameters is the composition of the air-fuel mixture. In a diesel engine, its range is wider compared to a gasoline engine, as a result of which it is difficult to unambiguously judge whether the mixture is poor or rich for a certain mode. Therefore, the diagnostician has to compare many indirect indicators. This is reminiscent of a detective investigation with weeding out suspects and gradually finding the true culprit.

deductive method

The most difficult task is to identify floating faults that leave almost no evidence and reveal themselves only in certain engine operating modes. Only an experienced diagnostician-detective armed with a good scanner can handle it. Luckily, over several trips, comparing key operating parameters of the main engine systems, he can catch the culprit. But often the diagnostician has to use workarounds to narrow down the suspects.

To describe the course of the investigation, consider the most common cases when a car arrives at the service with obvious and permanent malfunctions.

The fuel equipment is most often to blame for the difficult start of the engine and the instability of its operation in various modes. But it is important to ensure that other causes are excluded - for example, problems with the cylinder-piston group, namely a decrease. You can’t just measure it on a diesel engine, you will have to dismantle the fuel injectors or glow plugs, which is fraught with damage. This is where specific diagnostic methods come to the rescue.

First, using a scanner, they check the fuel supply correction for the cylinders and the dynamics of changes in fuel pressure in the rail. The control of these parameters is included in the vehicle's on-board diagnostic system. If the pressure in the rail is built up more slowly than expected, a check is carried out using external meters. First, cut off the low pressure line to the injection pump by connecting a pressure gauge or vacuum gauge (depending on the type of supply circuit). Next, check the pump. A pressure tester is connected to it so that the high-pressure fuel pump pumps fuel "into the wall": in the starter scrolling mode, it develops the maximum pressure, which is compared with the required one. By the difference in indicators, the condition of the pump and its metering valve is assessed.

With the help of this tester, the correctness of the readings of the fuel pressure sensor in the rail is also checked. In this case, the device is connected to the ramp instead of one of the fuel injectors (it's okay that it will temporarily work without one cylinder). The tester and scanner readings are compared and the lying sensor on the ramp is cut off.

By analyzing the values of the correction of the fuel supply, problematic cylinders are reliably identified. If one of the injectors is underfilled or the combustion pattern of the air-fuel mixture is disturbed due to a decrease in compression, the engine control unit will try to correct the situation by increasing the injection duration. In this case, the correction values will differ markedly by cylinders.

Next, the diagnostician calculates the culprit: is it an injector or a decrease in compression in the cylinder? The second parameter is often evaluated indirectly so as not to unscrew the injectors or glow plugs to connect the compression gauge: they are easy to damage, especially for engines with high mileage.

The first method is included in the on-board diagnostics functions of some car brands. According to the uneven rotation of the crankshaft at the time of its scrolling without starting the engine, the “brains” themselves determine the spread of compression across the cylinders. This is an express method with low accuracy and repeatability of results. He is able to calculate only heavily passed cylinders and will not notice less obvious deviations that may affect the operation of the engine.

The second indirect method of measuring compression is more universal. A sensor is hung on one of the battery wires, which registers the peaks of the current consumed by the starter when the crankshaft is scrolling. The higher the compression in the cylinder, the greater the consumption in the compression stroke. The sensor is a current-to-voltage converter. It is connected to an oscilloscope, and already on its screen, the values \u200b\u200bof the peak voltages across the cylinders are compared. If they are the same, then the compression in the cylinders is considered optimal. Otherwise, using synchronization with other signals, it is possible to “tie” specific cylinders to current peaks. Or go further - take a real measurement, simultaneously using a compression meter and a current sensor. Then for a particular type of engine, we get correlated (interrelated) values (amps and bars) that will be useful in the future.

If the compression in all cylinders is normal, we direct all attention to the fuel injectors. The electrical part of the injectors is checked with a tester, which measures their resistance and inductance, and also checks the insulation resistance. The hydraulic part (as well as the high-pressure fuel pump) can be fully tested only on expensive stands, which are mainly available to specialized enterprises for the repair of fuel equipment. In the arsenal of conventional service stations there is only a familiar kit for checking the so-called return line (a line for draining fuel from the injectors into the tank). Connect volumetric flasks to the nozzles and watch how they are filled. At the same time, it is not at all necessary that, for example, an injector that decently underfills fuel into the cylinder will drain much larger volumes into the return line compared to others. This test is carried out in addition to other activities. If you draw unambiguous conclusions only on the basis of its results, you can groundlessly condemn workable elements.

EAGLE AND TAIL

Branded diesel technical centers (for example, Delphi-Service or Bosch-Service) are far from being in all cities. Car owners are left with ordinary mono- or multi-brand car services.

Monobrand services that specialize in one brand or several, but belong to the same concern, usually have a large but narrow experience. Over the years, they have stuffed a lot of bumps on some models and often, even without diagnostic equipment, they can immediately diagnose the symptoms of malfunctions. And they usually have the ability to temporarily supply known-good items to pinpoint the culprit.

But even such service stations sometimes fail. There has always been a significant turnover in this area. Sooner or later, a seasoned specialist leaves for another technical center, and a less experienced master takes his place. In addition, if some complex defect has not yet been encountered by service diagnosticians, their system knowledge, as a rule, is not enough to make an accurate verdict.

Employees of multi-brand services are usually more savvy in fundamental matters: obliges the flow of various machines and systems passing through their hands. This is not about "temporary workers", who have one universal Chinese scanner for all occasions, but about serious service stations. Professionals use a wide range of diagnostic equipment and check many parameters. However, sometimes it takes them much longer to make a correct diagnosis than their colleagues from a monobrand service. And they will not be able to perform some complex procedures due to the lack of narrow-profile equipment or equipment.

Standard scheme

Diagnostics of other diesel systems is easier, but you still can’t do without special equipment. Before removing the glow plugs for inspection, measure their voltage and resistance. The best test is to connect a current sensor used to measure compression. Usually candles are controlled by a separate block. The sensor is hung on its supply wire and the total current consumption is recorded: by its significant drop, you can immediately determine that one or two candles are not working. Next, we move on to checking specific candles.

For diesel engines, the vacuum system is usually more complex than for gasoline engines, therefore, auxiliary equipment, a smoke machine, is often used to check the tightness of its lines. Leaked smoke will definitely indicate a leaky place. This apparatus is also used to check the tightness of the intake tract of the pressurization system. But its control part (if it is of a vacuum type) is tested in a combined way. The readings of the vacuum gauge connected to various points of the system are compared with the data received from the scanner on the control action on the solenoid and boost pressure.

The condition of the particulate filter can be accurately read by the differential pressure sensor. In any diesel car, the on-board diagnostics of this unit is very developed, and it is quite enough to obtain accurate data. The fact that the filter is clogged above the permissible level will be indicated by increased back pressure in front of it.

The operation of the exhaust gas recirculation (EGR) valve is also relatively easy to check. Electric valves are usually equipped with a feedback position sensor. The air consumption of the engine is also taken into account. A diagnostician using a scanner is able to determine the condition of the valve and its incorrect operation.

When running a diesel - a separate issue. Against the background of the general loudness of the motor, it is difficult to determine their true source. The main noise of a diesel engine is associated with the characteristics of the combustion of the air-fuel mixture in the cylinder. If it takes on an anomalous character, for example, due to a faulty injector, the sound is amplified. In this case, turn off one nozzle at a time to determine the "loud" cylinder. As soon as the desired one is deactivated, extraneous noise will disappear. True, such a maneuver will not work if two or more cylinders are noisy.

NOT A PANACEA

A full diagnostics of diesel fuel equipment can be carried out only in the branded technical centers of the manufacturers of these systems. In their arsenal there are multifunctional stands for testing injectors and high pressure fuel pumps in various modes and equipment for repair. But even such a technical base does not always give a 100% result.

There are cases when proven injectors are installed on a car that have successfully passed all the tests at the stand, but the malfunction does not go away. And the reason is not in useless equipment or low qualification of employees, but in specific operating modes of fuel equipment in real conditions - even the most sophisticated stands are not able to recreate them.

Often there are problems with repaired parts and assemblies. far from every service station can carry out such work, and even with a competent approach, misfires are inevitable. In some cases, the restored injector, which has passed all the checks, refuses to work adequately at all, and in others it is capricious only in some engine operating modes, although the test bench ran it through all the control points and assigned the correct fuel correction code. As a result, you have to change an expensive nozzle, despite the fact that the owner of the car has already spent a lot of time and money.

Thank you for your help in preparing the material, the training and practical center of the company Interlaken-Rus.

Buying a used car is a rather responsible procedure, as it involves a large number of legal and technical checks. As for technology, that is, an analysis of the state of the vehicle itself, when buying a used car, maximum attention should be paid to the most expensive elements: the body, engine, transmission, individual components of the chassis and steering.

If the condition of the body can be assessed visually, and the serviceability of the chassis can be easily checked on a lift and tested on the road, then it is not so easy to solve the issue with the engine. As a rule, the seller will not allow you to open the motor for diagnostics. Similar difficulties arise when it is necessary to check the removed engine at.

In this article, we intend to talk about how to check the condition of the engine when buying a car on gasoline, as well as what methods help to check when buying a car.

Read in this article

We check the used engine before buying

To begin with, a lot about the condition of the engine can be found out by visual inspection of the engine itself and the engine compartment. First of all, you should remember that an externally clean engine that starts and runs does not mean that the engine is fully functional and in good condition.

Experienced craftsmen at service stations are well aware of this, car dealers and not entirely honest sellers are also well aware of this. For this reason, when assessing the condition of a used one, you need to clearly know what to look for.

So, let's figure out how to check the engine when buying. First of all, even if you do not have much experience, it is not at all necessary to tell the car dealer about it. Try to refrain from any unnecessary comments, while following the instructions step by step, which we will discuss below.

Before starting the inspection of the motor, start with simple questions regarding the repair and maintenance of the car and engine. Ask what and when was done on the motor, at what mileage was the last time, when it was produced or, antifreeze, spark plugs, etc.
Also ask about the type and brand of oil filled (for example, 5W30 or 10W40) and other technical fluids. In parallel, observe the clarity and transparency of the answers and the reaction of the owner.

This approach will immediately allow you to identify either a reseller who does not know the history of the car, or a careless owner who did not pay proper and timely attention to the car.

Visual inspection of the motor

Next, you can proceed to inspect the engine. If the seller prohibits or deliberately makes it difficult to access individual external elements under the hood, then it is better to immediately refuse to buy such a car. If there are no problems, you can continue.

As we have said, the first thing you need to pay attention to is traces of engine oil. Oil drips or traces of antifreeze will indicate leaks through gaskets, seals and other seals. In some cases, such problems can then be fixed without major financial investment, while in others, oil can be squeezed out as a result of serious engine malfunctions.

It turns out that a worn gasket or an oil seal can leak, which is not so difficult to change. However, in some cases, similar leaks may occur for other reasons. For example, when the engine was overheated, it could then "lead", that is, the geometry of the mating plane is violated. As a result, replacing the gasket does not solve the problem.

We add that even if nothing serious happened to the engine, a dirty internal combustion engine with smudges will indicate that for some reason the owner does not pay due attention to the condition of the vehicle, carelessly operates the car, etc. This suggests that the maintenance schedule, oil changes and consumables could be systematically violated, which is very bad for.

in order to give a general presentation to the car;
to hide the drips of oil and technical fluids;

Unfortunately, the second case is much more common, since a serviceable motor is rarely washed before being sold. Moreover, the sellers separately draw the attention of the buyer to the fact that the motor is dusty and the engine was not specially washed, that is, it is clearly visible that there are no leaks.

Either way, leak detection is a cause for concern and/or bargaining. A clean motor should also be alarming, which will require a more thorough check. The best option can be considered an engine that is covered with a small layer of old dust, while not having smudges.

Checking the condition of oil and antifreeze

If you do not know how to check a diesel engine upon purchase, or if you are interested in checking a gasoline unit, then you should start by assessing the condition of the technical working fluids inside the internal combustion engine. We are talking about engine oil and coolant.

Let's start with oil. The first step is to unscrew the oil filler cap. Ideally, the lid itself should be free of obvious oiling from the outside, the inner surface should also not be dirty, with traces of oil foam, etc. The last statement is also true for the neck walls.
Next, you can get the oil dipstick and assess the condition of the oil. If it is fresh, transparent, has no foreign impurities and foam, then it will be difficult to quickly determine anything. Black oil indicates that either the lubricant has not been changed for a long time, or as a result of general contamination of the internal combustion engine and the presence of malfunctions.

It should be especially alarming that the oil in the engine can foam, that is, it forms. In this case, it becomes obvious that liquid from the cooling system enters. Note that in such a case, either immediately bargain with the seller for the cost of a similar contract motor /, or stop further inspection.

As for checking the engine in the cooling system, the task is to determine the breakthrough of gases and their entry into the specified system, as well as to identify the possible appearance of traces of oil in the coolant. For diagnostics, it is enough to open the cap of the expansion tank. If traces of oil are visible, the coolant is bubbling in the reservoir with the engine running, then the problem is obvious.

In some cases, the culprit may be broken, while in others, the possibility of hidden ones should not be ruled out.

Diagnostics of the state of the engine by spark plugs

Checking spark plugs reveals a range of potential engine and system problems.

Pay attention to things like:

oiling;
black, red or white soot;
traces of unburned fuel;

The above and other signs are a clear indicator of certain problems. It is worth considering, since checking the engine by the color of soot and the condition of the spark plugs is an effective method only subject to certain conditions,.

Extraneous sounds and engine vibration

Evaluation of engine operation at the initial stage involves the identification of extraneous sounds, tripling, misfiring and ignition of the mixture, as well as other malfunctions in the operation of the internal combustion engine.

After the engine has been started, you need to listen to its work, and also look at the level of shaking and vibration. If possible, you can use a stethoscope, which will allow you to listen to hidden defects and localize suspicious noises.

We note right away that knocks of different tonality and frequency, as well as uneven operation, indicate problems. If the gasoline engine runs like a diesel engine, dips occur when you press the gas, the unit shakes violently, etc., then malfunctions are obvious.

Both various systems (ignition, power) and individual components inside the internal combustion engine can fail. The crankshaft, pistons, hydraulic lifters or valves, connecting rods, etc. can knock. Shaking and vibrations are the result and a sign of breakdowns, but the possibility of problems with the engine mounts should not be ruled out either.

Exhaust gas color analysis when checking the motor

The color and intensity of the exhaust, as well as the composition of the exhaust gases, in many cases clearly indicate the presence or absence of problems with the engine and its systems.

Let's start with the fact that on a properly heated injection engine in the warm season, no smoke is practically visible. There is also no exhaust smell. In the case of a carburetor, a slight grayish-white smoke can sometimes be observed, the smell is distinctly present.

So, if the engine runs smoothly, does not smoke, does not knock or vibrate at idle, and also quickly and clearly responds to pressing the gas pedal, then you can make a test drive.

Let's make a reservation right away, a short drive will not be enough. It is important to evaluate the operation of the unit in different modes, as well as warm up the engine to operating temperatures. For this reason, you should count on a segment of the path of at least 10-15 km.

To solve the problem, you should offer the car seller a reasonable compensation for the spent fuel and time costs. Next, you need to ask the owner, who will be with you in the car, not to make noise. You will also need to turn off the speaker system in order to be able to listen to all extraneous sounds.

First of all, take a look at the dashboard, not . At the same time, evaluate the sound of the engine when picking up speed, during, during sharp acceleration, etc. Also, while driving, you can listen to the engine alternately with the driver's and/or passenger's window open and closed.

While driving, pay attention to jerks, vibrations, knocks and whistles. If nothing of the kind is revealed, then at the end of the trip, immediately open the hood and evaluate the external state of the warmed-up internal combustion engine. The presence of fresh smudges on a clean engine will indicate problems that the seller wanted to hide by first washing the engine compartment

Again check the level and condition of the oil, also let the unit cool down a little and look into the expansion tank, evaluate the condition and type of coolant. Smoke should not come out of the tank, there should be no oil stains on the surface of the antifreeze.
If the situation allows, you can re-unscrew the candles and re-evaluate their condition. In some cases, it is possible to negotiate with the owner and even produce (if the buyer has a compression tester).

As you can see, a superficial inspection and inspection of the engine before purchase reveals a large number of hidden defects with the right approach. If you are not confident in your abilities, then the right decision would be to order a comprehensive diagnostics of the power unit and the entire car at the service station. Specialists will conduct, indicate the presence of possible problems and immediately announce the approximate cost of repairs.

In the future, the information received can be used as a weighty reason to refuse a purchase or a reasoned bargain. Finally, we add that for quick diagnostics of cars with it is useful to have a compact diagnostic. The device allows you to quickly scan the system for errors, as well as evaluate the operation of engine systems in real time.

More recently, automakers have amazed the world with the release of diesel versions of sports cars. The Audi TT, the Škoda Octavia RS or the Peugeot 406 Coupe seemed to encroach on the core values of sportiness: a manual transmission, rear-wheel drive and a petrol engine. Probably, it could not have been otherwise - the opportunity to drive in style and economically seemed too tempting.

Diesel "Audi TT"

In the last decade, diesel models have become popular in most vehicle classes, from small city cars to large all-terrain vehicles, as well as the already mentioned sports cars. People choose used diesel models even despite the somewhat higher operating costs - everything is overshadowed by low fuel consumption.

Here are some tips on how to test a diesel car yourself when you buy it. By following the steps already mentioned, you will reduce the possibility of acquiring a bad vehicle:

Unscrew the oil fill cap, but do not remove it. Ask the owner of the car or the person accompanying you to hold down the accelerator pedal of the car for a while. Check the cover: if the engine pulls it in, everything is fine, if it pushes it out, the engine compression is probably already too low.
Inspect the lid itself - there should not be any deposits of a pasty consistency on it. If they are still there, this may indicate an overheated engine or an untimely oil change.
Until the owner of the car or your friend got out of the car, ask him to press the accelerator pedal harder. Keep an eye on the exhaust pipe: if what you see resembles a light black smoke, it's okay, but if thick bluish smoke pours, you may have to change the turbine in the near future.
Select the so-called oil dipstick and pay attention to whether steam or smoke rises from the hole. They shouldn't be. True, this advice does not apply to new cars.
Do not rush to turn off the car engine. Let it warm up to operating temperature. Then turn it off, wait 5 minutes and try again. The motor should start running instantly. If this is not the case (i.e., the engine starts to work only after 2-3 rotations of the crankshaft), you will probably have to visit a car service in the near future.
Avoid the V-shaped 2.5 TDI engine, which was installed in the cars "Volkswagen", "Audi", "Škoda". Due to its defective design, it requires more maintenance and cannot always answer with its durability.
Keep in mind that even in a new car, the engine can be dirty and, experienced people say, this is nothing to worry about. The main thing is that there are no traces of oil smudges on it, indicating more serious problems. So take a close look at a ten-year-old car that has a clean engine. Washed it, probably not in vain. And it is better to be accused of morbid suspicion than to buy a bad car.

Good luck with your choice!

So, you have decided to buy a car with a diesel engine. For a post-Soviet person who did not work in the past as an Ikarus or KAMAZ driver, the word "diesel" always aroused a kind of sacred awe - this creation of the human mind seemed to be a very complex, dark and incomprehensible subject. Therefore, a daredevil who decides to take such a desperate step - to drastically change his usual gasoline life and buy a car, not only is it imported and not new in the vast majority of cases, there are many questions about what to do with this car before and after purchase.

Do you want to buy a diesel car

What should you pay attention to when buying? To begin with - for everything the same as when buying any car (general condition, mileage, corrosion centers, and so on). If you are buying from a stranger - don't let them know in advance of your plans to test something - catch them by surprise with the following test:

How to start a cold engine (in the morning, for example).
If you have to turn the starter at least a little more, this is already an alarming sign (wear of rings, piston). In this case, it is desirable that the engine be completely cold when starting. A serviceable diesel engine should start with half a turn. Cold diesel noise, quite noticeable. Warmed up - much quieter. Try to start a hot engine, on some models the heating does not turn on and the start is due to compression.
My car has a similar pattern. On a cold one, it starts with half a turn, and on a hot one, you have to make from 3 to 10 attempts. After disassembly, the diagnosis was confirmed - the wear of the rings. However, this may not happen on all machines: some have a sensor - if the temperature on a warm engine is insufficient to warm up the combustion chamber, then the glow plugs turn on. Another thing is when this sensor does not work.
and the condition of the fuel equipment.
When you press the accelerator on a warm engine, check for smoke coming out of the exhaust pipe. If the smoke is dark, then, most likely, the oil scraper rings are worn out, or the injectors are out of order, in general, nothing good. If it's white smoke, water is getting into the fuel somewhere.
A simple method: put a piece of paper under the exhaust and look - if there is soot, then most likely it is eating oil (oil soot) or incomplete combustion of fuel. If there is a turbine, then black smoke can go until it is turned on. On the move, there may be black smoke when re-gassing, but it is short-lived and not thick. Smoke may also be due to a clogged air filter - try running the engine without it.
The sound of the engine.
If the sound is uneven, tapping, it is possible that the valve clearance is incorrect in the engine, or something is wrong with the valves themselves or the piston. It is possible that everything can be corrected with elementary adjustment. By the sound of the engine, you can also assess the condition of the fuel equipment: - "hard" sound, black smoke at high speeds - early injection angle; - interruptions and gray smoke at idle and black smoke and interruptions at high - late injection angle; - uneven idling and black smoke - a non-working nozzle, you can definitely determine this by turning it off. The pump should not "strum".
The engine should work softly, - "rumble" solidly, in a word, "in a diesel way". Try to hear (although it is difficult on an unfamiliar diesel engine) extraneous noises at different speeds, when they are set and reset, how the piston and crankshaft work.
Open the oil cap.
If oil squirts from the oil filler neck, this is an indicator that there is a gas breakthrough somewhere (or maybe the guides are just broken). This thing, though unpleasant, but not fatal. There can be many reasons - both serious and curious.
At the same time, you can seriously bring down the price - shaking your head and speaking out in this way: “Yes, you, man, the engine is dead! that this is not so - in life it will not prove until the compression is measured.
General view of the underhood.
Determine if the nuts of the nozzles, cylinder block, traces of white or red sealant (for the Japanese - only black) are not jammed - it means that they climbed into the engine here. All accessory mounting bolts must be in place. Only in our service they can easily not put a hard-to-reach bolt.
The condition of the liners can be assessed by warming up the car, turning off and immediately turning on the ignition: the oil pressure light should light up after a couple of seconds. If earlier - either the oil is liquid, or the liners are not in order. The second is faster.

More complex procedures:

If you have completed all of the above steps and after that you are not disappointed in life, then this is already good. Even better if you still want to buy the same car. Then, if you have the opportunity, it is strongly recommended to perform the following actions, which speak volumes (at the station or, if possible, better with friends).

A. Measure the compression. Correctly it is measured like this:

Unscrew all injectors.
The starter “flashes” the cylinders a couple of times to prevent oil or fuel from entering the cylinders, which can affect the compression value.
Screw the compression gauge into place of the nozzle and turn the engine several times with the starter until the arrow stops.
Everything is repeated on other cylinders. Compression should be, firstly, not lower than 25, although it may be different for each volume. The smaller the spread of values by cylinders, the better. The standard for a new car is 0.5, no more. For an old car, this, of course, is not feasible, but if there are values like 18-25-30-22 at a rate of 25, this indicates the possibility of an early overhaul.

If the compression is low, it's not the end of the world. To begin with, you can find out what is the cause - and, accordingly, how much the repair will cost. Low compression happens for two reasons:

Piston wear (there is a breakthrough of gases through the gaps between the sleeve and the piston)
Valve wear (gas breakthrough through guides, seals).

To check, take a little oil in a syringe, inject into the nozzle hole, screw in the compression gauge again and measure the compression again. The idea is simple: if the rings are worn, oil flows into the gaps and does not allow the gases to break through, and the compression should increase. If it remains as it was, then the valves are worn out, which is both cheaper and easier to repair. Yes, and do not inform the seller of your intention in advance - otherwise they will pour in some filth to increase compression, then you will not end up with problems.

B. Check the injectors. A normal nozzle, when fuel is fed into it under pressure, should emit a very characteristic "beech-beech-beech" and spray "into the fog": All sorts of rain and trickles are not welcome. Increased black smoke may still be present if the cut-off in the injectors does not work. Sprayers need to be removed and inspected. Spraying in the form of drops and streams is categorically not recommended - you can burn the pistons or the head, depending on where it sprays. Determine the condition of the fuel supply and return hoses. If the tightness is broken, then there will be problems with starting.

B. Glow Plugs/Heated Combustion Chamber. The inclusion of the heating relay is checked by ear and by the lights on the dashboard. By the speed of switching off the relay, it is possible to determine idle candles. Using a voltmeter, you can first trace that 12V is supplied to the candles. After starting or after 5-10 seconds, it drops to 6V, and after the engine warms up - to 0. But on different machines in different ways. If the candles, designed for 8 sec. put on a car with a relay that gives out 13 seconds, there is a high probability that they will burn out. And the speed of turning off the relay does not mean anything at all - it gave out 10 seconds. and turned off, and the candles may be faulty. What’s more, we can’t tell anything by ear.

D. Oil color. The color of the oil is black, without foreign inclusions. A quick, somewhere in 500 kilometers, darkening of the oil after changing it (not due to a mixture with the old one) is an indirect sign of wear on the rings. If the oil has a characteristic silvery-gray tint, then there is a fairly high probability that the engine has been "treated" with some kind of molybdenum additive.

D. Cooling system. There should be no bubbling in the cooling system, this is checked at medium and high speeds on a warm engine. If there are bubbles, the gasket has burned out, or the cylinder head has moved. Estimate the thermostat response time, the engine at idle may not warm up above 40-60 degrees, but after 5 minutes of driving, the arrow on the scale showing the temperature of the coolant should show the operating temperature. On the iron pipes of the cooling system near the block there should be no rust and a characteristic red coating, like the exhaust manifold - a suspicion that it was overheated.

E. Measure crankcase gas pressure. High pressure indicates, again, the wear of the piston or valves.

Immediately after purchase

If you are not afraid of all of the above, and still bought a car, then immediately perform the following magical steps:

Change the timing belt immediately after, no matter what the seller tells you there. Take a branded belt, do not buy cheap. If, God forbid, it breaks, the valves cover at least. Have the belt changed by a specialist. I saw an Audi with a head of the block torn off and thrown into the trash only because the owner was stingy to buy a good belt.
After purchase, watch the oil level. If the level drops without visible oil leaks, this is a clear sign of worn oil scraper rings.
Change the oil and fuel filters, regardless of when the dealer says he changed them. Especially if you bought a car on the eve of winter.
Naturally, when performing the above actions, it is desirable to change the oil. I recommend: Shell Helix Ultra Plus 5W-40 synthetic. Started at -33° even with very poor compression. P / synthetic Chevron Diesel SAE 10W40 API CF / SE plus REDEX molybdenum additive. By the way, it is best to take oil with API CF or CE classification. CF is the best. CC and CD are designed for diesel engines operating at medium loads, which is not very suitable for our fuel. Abroad, for old diesel engines, it is just right, but in our country all conditions must be considered the most difficult and unfavorable, and oil should be taken accordingly.
In addition, study the numbers on the battery that you got with the car. A diesel engine, especially if it does not have very good compression, needs a good battery to start the engine (recoil current: the more the better), thinner oil and a working heating system. I have, for example, 100Ah / 450A at - 18.
Also, as a primary event after the purchase, we advise you to carry out diagnostics at the service station (costs from 30 to 60 dollars), which can tell a lot about the car. Although the stations are also different and they can say different things. So don't be too scared. It is best to ask the opinion of several experts (they tend to be very contradictory).

Some time has passed since the purchase

So you're driving your newly acquired diesel car, and hopefully getting a lot of buzz out of it. But somewhere in the depths of the soul, the thought torments: “Now it’s good, but some time will pass and ....” What should I do to prevent this “and ....” from happening? It is difficult to advise here for all occasions, but some general advice can be given:

Avoid "cheap" options from nowhere (tractor, ship, diesel diesel fuel). It's very hard to guess here. We once took a chic diesel diesel fuel, but our friend, or rather, his car, suffered greatly from the ship's diesel fuel. Refuel only if someone already drives this diesel and is satisfied with it.
Change the fuel filter more often than required by the service book. With the quality of our fuel, this is a decisive factor for the normal operation of the machine, especially in the cold season. You can put an additional fuel filter.
Do not spare money on oil, especially for winter. For our winters, mineral water 10W30, semi-synthetic 10W40, synthetic 5W40, other SAE markings are best - see the catalog for temperature limits.
Fuel and oil additives.

We do not recommend getting carried away with the addition of additives, especially cleaning ones, and especially of unknown production. The cleaning additive has the ability to wash out all the dirt and muck from the tank and pipelines and drive it all into the fuel pump, the filter cannot hold everything. The result is high repair costs for the pump and/or motor.

For the winter, you can stock up on anti-gel. I use Kleen-Flo (Canada) and REDEX (GB). Antigel should be added to the fuel according to the instructions and until the diesel fuel thickens. After that it won't work anymore. Although diesel fuel from new, decent gas stations at a more or less low temperature (about -10-15) should not gel much.

I highly recommend the REDEX molybdenum oil additive. Firstly, the molybdenum compounds contained in it enter into molecular interaction with the rubbing surfaces in the engine and create a thin protective layer that reduces wear and friction. Secondly, these compounds tighten microcracks and small surface damage. It lasts for 75,000 kilometers, i.e. the protective layer is not washed off at. In practice, this is expressed in a sharp decrease in engine noise and fuel economy. This is not an advertisement, I tried it myself and am very satisfied.

You can also add a few so-called conditioners, i.e. additives designed to improve fuel performance. Manufacturers attribute to them the magical effect of binding water, increasing the cetane number, reducing consumption, etc. I gradually add again the REDEX conditioner. It doesn't seem to do any harm. Try to buy all fuel additives from the same company. They all seem to be compatible, but it's better not to risk mixing additives from different companies.

Do not experiment with additives to increase compression - when you need to replace rings - "You can't revive a dead man with poultices", and they can do much harm.

Never buy a car without first checking it in motion.

Body and wheels.
These nodes are required for verification, it is better to entrust this procedure to knowledgeable people. There may be hidden defects in the body.
And the wheels are those 4 points that connect your car with the road, if the tires are used, they need special attention.

But still, in a diesel car, the main thing is the engine.
During testing, pay attention to the softness of the clutch pedal and gear lever, the steering wheel, which should turn without significant effort.
You should also make sure that the accelerator pedal operates smoothly, steadily and without sticking, and the speed drops immediately after the pedal is released. If this is not the case, then the cause of the problem may be a clogged fuel drain line or fuel leaking from the high pressure fuel pump.

Uncontrolled fluctuations in the frequency of rotation of the crankshaft.
Some diesel vehicles are subject to the phenomenon of uncontrolled fluctuations in the crankshaft speed. In this state, the vehicle picks up speed instantly regardless of the position of the accelerator pedal, which is usually caused by air being sucked into the fuel system. This shortcoming can be corrected, but sometimes it will take several hours to
find a leaky spot. If the car suits you in every way, except for uncontrolled fluctuations in the frequency of rotation of the crankshaft, then do not refuse it, just demand that this drawback be eliminated before buying.

Hypothermia.
Keep an eye on the temperature gauge while driving: if it never goes past the second half of the scale, then there is a possibility that the engine has been running at low temperatures for too long, which negatively affects the operation of the lubrication system, fuel efficiency and leads to increased wear of internal parts engine. Engine operation at low temperatures may be accompanied by the appearance of a white deposit or deposits inside the oil filter, oil sump breather hose and on the dipstick. This car is not worth buying.

Overheat.
Watch the temperature gauge for overheating, which is even more dangerous for the engine. Overheating is usually caused by inefficient operation of the cooling system, which is caused by scale and rust in the system, radiator contamination, air locks, or insufficient coolant. Check the coolant level and look for possible deposits in the pipes.
Other possible causes of overheating are incorrect fuel injection timing (which is easy to fix) or faulty injectors (which are more expensive to repair). If you have a suspicion that the engine is prone to overheating, avoid buying such a car, as overheating can lead to engine failure.

Attention! Under no circumstances should the engine be run without coolant, as severe damage may result. Carefully monitor the condition of the cooling system hoses, as a coolant leak can lead to irreversible consequences.