What is the reason that sometimes on a completely new car does not start diesel engine ? In order to understand this issue, you should start with the basics, namely, understand what this type of power unit is.

Diesel engine does not start - study the device and principle of operation

Diesel engine is one of the types of engines internal combustion, in which ignition of the combustible mixture in the combustion chamber occurs as a result of its compression. During operation, the air in the engine cylinder, with increasing pressure, instantly heats up to 700 o C, resulting in fuel ignition.

If, for example, in a gasoline engine, ready-made air is supplied from the carburetor to the cylinders. fuel mixture, then they enter the diesel engine separately. In this case, fuel is injected by nozzles under a pressure of 220 MPa, which contributes to its strong atomization and rapid ignition.

At the dawn of the automobile industry, engines were mainly installed only on trucks, since they differ more high power compared to gasoline ones. In addition, diesel engines significantly benefit in terms of fuel economy. But, despite all their advantages, diesel engines still have some disadvantages; they can be called whims rather than serious flaws, which in most cases manifest themselves in difficult operating conditions.

One of the main reasons why a diesel engine does not start is non-compliance with the rules of its operation and violation of the terms and procedures of work. For example, it is recommended to change the oil after the car has driven 7,500 km, which is due to the high content of domestic fuel sulfur.

Because of this, rapid oxidation of the oil occurs, as a result of which it loses its performance qualities, which negatively affects the condition piston group. It is also necessary to carefully monitor the condition of the fuel system and regularly drain sediment from the tank and fuel filter. It is recommended to wash the tank twice a year, which will protect the filters from premature clogging.

The performance of a diesel engine is greatly influenced not only by the quality of the fuel, but also by its suitability for the operating season. After all, sometimes the reason why it stalls in winter is the use summer stamps fuels that low temperatures ah turn into a viscous mass. As a result, the fuel pump is simply unable to supply it to the engine. And since the pump is lubricated by fuel, in its absence, accelerated wear of the equipment occurs.

If this happens, then the only way to start a diesel engine is to drive the car into a warm garage and heat up the fuel.

How to start a diesel engine correctly and other nuances of its operation

One of the reasons that a diesel engine stalls while driving is that the fuel lines are leaking, clogged, or unsuitable for use. fuel filter, which may fail due to low-quality fuel.

Sometimes car owners cannot understand why it won't start. diesel engine, although yesterday everything was fine. The reason may be a breakdown fuel pump, which, unfortunately, is almost impossible to repair on your own.

Another one characteristic malfunction– the diesel engine starts and stalls. What could be the reason and how to eliminate it? In this case, experienced drivers first of all pay attention to the work fuel equipment and condition air filter. Perhaps they are simply clogged and the engine lacks both fuel and air.

One of the problems of novice car enthusiasts is violation of the rules for starting the engine. They simply do not know how to start a diesel engine correctly. If the diesel engine is in good condition, then it starts without problems both in winter and in summer. The main thing is that you should not start driving on a cold engine.. And when starting in winter time It is always necessary to use glow plugs - this will significantly speed up the process.

Expert opinion

Ruslan Konstantinov

Automotive expert. Graduated from Izhevsk State Technical University named after M.T. Kalashnikov, specializing in “Operation of transport and technological machines and complexes.” Experience professional repair cars for more than 10 years.

A diesel engine is significantly different from a gasoline-type internal combustion engine. Such power unit There are many reasons why a poor start or its absence is possible. One of the main reasons is low compression, due to which insufficient compression occurs and the fuel mixture does not ignite. In this case, you can pour a little motor oil into the cylinders through candle wells. This will help start the engine, but the problem with low compression will not go away; the oil will burn out over time.

The next reason for the inability to start a diesel engine is the complexity of the fuel system. Problems can be identified by the color of the smoke coming from exhaust pipe. If, when the engine is rotated by the starter, the exhaust color is blue, it means that fuel is supplied to the cylinders, but there is no ignition. If the smoke turns black when you press the gas pedal, there is a problem with the high pressure fuel pump (HPFP) or injectors. Usually, if there are problems with the fuel injection pump, the engine stalls. The diesel fuel pump is almost impossible to repair due to the complexity of the device, so you should replace it, but you need to be prepared to fork out some money. injection pump and diesel injectors Depending on the car model, they are quite expensive.

The starter turns but the engine does not start - the driver of any car is not insured against this, not only in severe frost, but also throughout the year. Possible reasons for this different engines completely different. This means that the scheme for finding the reason why the car does not start should be selected based on whether you have a diesel engine.

Diesel engine

A diesel engine is fundamentally different from a gasoline engine in the way the fuel is ignited. At the end of the compression stroke, the air temperature in the combustion chamber rises to more than 700 ° C. At this moment, atomized fuel is injected there, which ignites upon contact with hot air. Due to the high thermal conductivity of the block head, part of the thermal energy obtained from air compression is inevitably removed by the cooling system; this part is greater the lower the temperature of the head and coolant. Therefore, so that the temperature compressed air did not fall below that required to ignite the fuel, before starting a cold engine, the air inside the cylinders is additionally heated with glow plugs. This is especially necessary when it’s frosty outside.

If a diesel engine does not start when cold, check the spark plugs first. Since with non-working glow plugs, a cold diesel engine is very difficult to start, even if the starter turns for a long time.

More often than not, in this case, the starter turns but does not engage. A cold diesel engine with faulty spark plugs has difficulty starting even at a temperature just below +5 °C, and even more so in cold weather. It may even seem that the starter is not turning well.

Checking the glow plugs:

First you should check whether the glow plug control unit is working properly. To do this, attach control lamp to the spark plug power bus and to ground and turn the ignition key to the on position; if the control unit is working properly, the control will light up. For further checks, turn off the ignition and disconnect the power bus from the spark plugs.

Methods for checking glow plugs:

If the starter spins for a long time and the car does not start, it is also possible that the high-pressure fuel pump (HPF) is aired out or the silencing valve is faulty. With these faults, the car will not start either in cold or warm weather.

Diagnostics can begin by checking the presence of power at the silencing valve (it opens when power is applied and closes when removed). The easiest way to check the power supply to the valve is with a test light; do not forget to turn on the ignition before checking. If there is power at the valve terminal, remove and put on the connector supplying it. The valve should make a clicking noise. If there are no clicks, the valve may be faulty.

Bleeding the fuel system:

A manual fuel pump will make it much easier to vent the system.

In the fuel line you need to find a place where the air will come out - unscrew either the plug in its upper part or the return of the injectors. If the fuel filter has a manual pump, turn on the ignition so that the damping valve opens and pump fuel until air stops flowing from the selected point and fuel flows. If your car is not equipped with a manual fuel pump button, and the pump low pressure It has electric drive, then after clearing the path for air to exit the fuel injection pump, it is enough to turn on the ignition for a while. When pumping fails, check the fuel filter; it may simply be clogged with dirt or paraffin.

Carburetor engine

If the starter spins for a long time and the carburetor engine does not start in cold weather, check whether you forgot to pull the starter cable (choke) toward you. Also check if there is a spark. For this high voltage wire remove the distributor cover from the ignition coil from the socket and fix the removed end at a distance of about 5 mm from ground. Crank the engine with the starter. The spark that breaks through this gap should be thick and blue. A thin orange spark indicates insufficient power and the need to troubleshoot in this direction ( possible reasons this: burnt contacts of the breaker or incorrect gap between them, bad contact ground coils, oxidized coil power terminal, unusable distributor capacitor). An excellent spark, about which one can say: “will kill an elephant,” forces you to move on to checking the fuel system. Possible reasons that the engine does not start related to the fuel system:

• Lack of fuel in the carburetor.
• Defect or misalignment of the starting device.

Fuel system check diagram:

• Remove the air filter cover.
• Pull the accelerator rod in one motion to fully open the throttle valves. If streams of gasoline fly out from the accelerator pump nozzles while the flaps are moving, it means there is fuel in the carburetor float chamber.
• If the accelerator pump does not report the presence of gasoline in the carburetor, try pumping it there manually. If you cannot pump gasoline in this way, check the cleanliness of the fuel filter, the carburetor sump mesh and the integrity of the fuel pump diaphragm. When both diaphragms of the fuel pump rupture, gasoline inevitably gets into the engine oil, the vapors of which, sucked through the crankcase ventilation, greatly over-enrich the mixture and make it difficult to start the engine. To assess in this case the amount of gasoline that has entered the pan, check the oil level and whether there is a smell of gasoline from the oil filler neck. If there is a smell of gasoline under the timing cover and the oil level in the crankcase has increased, engine repairs should begin with replacing the engine oil and filter (in this case, flushing is unnecessary).
• After gasoline is pumped into the float chamber, try to start the engine again.
• If there is fuel in the float chamber, but the engine does not start, evaluate the operation of the starting device. When the “suction” is turned on, the upper damper of the primary chamber should be completely closed, and the throttle valve of the same chamber should be slightly open by approximately 0.8 mm (the thickness of the semi-automatic welding wire).

Gasoline with direct injection

If the starter turns for a long time, but the injector does not engage in cold weather, the reasons may be the following:

The candles flooded. The stronger the frost, the more likely such an event will occur. If the frost is not very severe, you can try to dry them as follows: remove the connectors from the injectors and give the engine a good spin with the starter. Sometimes it helps. In case of prolonged failure, be careful not to drain the battery. The injector fills the spark plugs infrequently, but a car equipped with it also requires maintenance of the ignition system.

A situation often occurs when you turn the key, the starter confidently turns the crankshaft, but you cannot start the car. Some people run the engine until the battery runs out, in the vain hope that it might catch on. In fact, after two or three unsuccessful attempts should begin troubleshooting.

1 The engine does not start when the starter is running - possible damage

When the starter turns, but the engine does not start, it is difficult to immediately find the cause. You need to look for faults in quite a few places. Let's start with the starter. Turn the key again and listen to the sounds it makes. It should produce the characteristic smooth buzz of an electric motor without failures and nothing more. If you hear clicking, humming or extraneous sounds, we are looking for the problem in the starter. When in good condition, the engine most often does not start because fuel does not flow or it does not ignite.

If fuel is supplied, the ignition is in order, the starter turns, but the engine does not start, we look for the reason in the electrical equipment: we check individual sections of the electrical circuit and its elements. The reasons can be very simple: a fuse has blown, there is no contact due to a break or oxidation. Rarely, breakdowns of the electronic control unit do occur. Sensors can break down and send erroneous signals to the ECU, which incorrectly regulates the fuel-to-air ratio and its supply to the engine.

There may be a phenomenon when the engine shakes violently when starting, it seems to start, but does not catch. The reason may be electromagnetic interference, which prevents the sensors from correctly processing data and sending a signal to the computer. The electromagnetic field of the starter can create interference. If there are malfunctions of the crankshaft position sensor (CPS), the engine will not be able to start. In this case, fuel is supplied normally, the crankshaft is cranked well by the starter.

Starting malfunctions, when the starter confidently cranks the crankshaft, are quite common and do not depend on the type of engine.

2 Diesel - specifics of troubleshooting

Fuel ignition in a gasoline and diesel engine is fundamentally different. The compression stroke in a diesel engine occurs without fuel; it is injected at the very end, when the temperature in the cylinder reaches 700°. Fuel ignites when it comes into contact with hot air. Excess heat from the head is removed by the cooling system. To maintain the temperature inside the combustion chamber necessary for ignition of the fuel, cold engine before starting it is heated by glow plugs.

If a cold diesel engine does not start, we start looking for the problem with the spark plugs. The starter can turn for a very long time, but with faulty spark plugs, even at +5° it is difficult to start the engine, not to mention the frost. First, we check the serviceability of the control unit. We connect the light bulb to the spark plug bus and ground, turn the key. If the unit is working properly, the light will light up. Next, turn the key to initial position, turn off the power bus and check the glow plugs. We connect one contact of a 21 W light bulb to the candle, the other to the positive of the battery. If the spark plug is working properly, the light bulb burns brightly.

In any weather, a diesel engine will not start if the fuel pump is aired out or the shutoff valve is faulty. We check with a light bulb whether power is supplied to the valve. If there is one, remove and put on the wire that supplies it. A working damping valve makes a clicking sound. If the valve is in order, air remains in fuel system. We unscrew the return line of the injectors or the plug through which we will bleed air. If there is a manual pumping of the fuel pump, apply voltage to the valve so that it opens, and pump up diesel fuel until it flows instead of air. If the low pressure pump is electric, turn it on.

If it fails, when it is not possible to pump diesel fuel, we check the fuel filter: it may be blocked by dirt or paraffin.

3 Gasoline engine - checking fuel supply

The engine does not start if there is a defect in the fuel system: no gasoline is supplied, the starting device is faulty. To check the fuel system carburetor engine We carry out the following operations:

1. We sharply open the carburetor throttle valves, observing the injection of gasoline (the air filter cover has been removed in advance). If the fuel is atomized, it is supplied to the carburetor.
2. If fuel is supplied, but start cold engine impossible, check the starting device. Closing air damper– it should completely block the primary chamber, and the throttle valve should open slightly by 0.8 mm. To check operation throttle valve you will have to remove the carburetor.
3. When the accelerator pump does not supply gasoline, there is no gas in the carburetor. We pump it up manually and start the engine.
4. We check the operation of the fuel pump: remove the hose from the outlet fitting and pump it. After a few pumps, gasoline should squirt out.
5. If it was not possible to pump up gasoline, check the fuel filter and the mesh in the carburetor sump. Dirty filter change, wash the mesh.
6. Still not getting fuel? We disassemble the fuel pump and check the diaphragms. If they are torn, gasoline does not enter the carburetor, but into the pan, diluting the oil.

The oil should be changed; no flushing is necessary. We change the diaphragms, pump up gasoline and start the engine.

On cars with an injector, the engine will not start if the electric fuel pump does not work. Its serviceability is determined by a buzzing sound after turning on the ignition. Sometimes the reason is oxidized terminals or a fuse, but sometimes the pump burns out. May also be absent or be insufficient pressure in the ramp if gasoline got there. There is a valve under the cap on the side opposite the gas line connected to it. We press it - gasoline should spray out from there. If this does not happen, check the fuel filter, intake mesh, pressure reducing valve fuel pump (located in the gas tank).

4 Ignition - how to find and fix the problem

If the fuel supply problems have been corrected, but the car does not start, we begin to check the ignition. We unscrew the spark plugs and check for spark formation. We put a wire from the distributor cap on the spark plug, touch the metal on the car with the skirt, and at this time the assistant turns the engine with the starter. A strong spark is visible on a working spark plug of blue color. For injection engine the absence of a spark indicates a malfunction of the module, for a carburetor - the coil.

It is impossible to check the injector module at home, but the coil can be checked. On older models, one cylindrical coil is installed, on modern ones - a dual or monolithic module. The most advanced short circuits, which are installed on each cylinder directly on the spark plugs without wires. Coils with wires are checked simply: we pull out the central wire from the distributor, bring it to the metal of the car at a distance of 5 mm and turn on the starter. The presence of a spark indicates serviceability.

Often the distributor in a car fails - burning of the switch-distributor contacts does not allow the engine to start. If the distributor is non-contact, the Hall sensor may have broken down. This is not a typical malfunction - sensors rarely fail. Among the most common distributor malfunctions:

• the resistance on the slider has burned out;
• the distributor cover is burnt out;
• Hall sensor wires are broken;
• runout of the distributor shaft through worn bearings.

We check the distributor cover by replacing it: the car has experienced drivers Always stocked with a spare. Contactless ignition with a distributor has a switch, which is responsible for stable sparking. A faulty switch may cause the engine to not start. We detect the malfunction by hand - the broken switch gets very hot.

In cars with electronic system Most often, various sensors fail. The malfunction is recorded and an error message appears on the dashboard, each of which is assigned a code. Often ignition failures occur due to wiring when power is not supplied. Due to some ECU malfunctions, the engine cannot be started. We repair the unit at a car service center or replace it with a serviceable one.

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Despite the fact that obvious advantages have made diesel engines quite popular, cars with the “heart” of the Diesel cycle remain a rather specific technology. Therefore, it will be useful for every owner of a car running on diesel fuel to find out the malfunctions that cause a diesel engine to start poorly.

Let's look at the reasons why a diesel engine will have trouble starting:

• frosty morning;
• after a long stay;
• on hot, when the internal combustion engine is warmed up;
• The starter turns, does not engage, or starts, but then immediately stalls.

Specifics

The fact that diesel, like gasoline, converts the reciprocating movements of the piston into mechanical work, is self-evident. To better understand the reasons bad start, let's talk about the specifics of the Diesel cycle.

Motors of this type do not have a coil, distributor, GDP and spark plugs as such. He does not need them, since self-ignition of the fuel mixture occurs in the combustion chambers. The air entering the combustion chamber is compressed by the piston. This causes a significant increase in temperature in the combustion chamber. It is the high temperature fuel-air mixture causes diesel to ignite spontaneously. IN cold weather To facilitate heating of the air in the combustion chamber, all internal combustion engines are equipped with glow plugs.

Mechanics

Coking of piston rings

One of the reasons for poor cold starting may be normal wear and tear cylinder-piston group:

• production in cylinders, ellipse;
• occurrence, wear of compression rings;
• combustion chamber leakage and many others.

In winter or after being idle in cold weather, a “tired” engine with similar problems will be especially difficult to launch. Even good battery and a working starter will not guarantee a good start in the morning in cold weather. If before warming up the internal combustion engine smokes, does not develop any thrust, operates unstably or even stalls, and then the symptoms disappear when hot, pay attention to the “compression” item. Special attention. Please note that hot worn diesel internal combustion engine will start without problems.

Since the usual measurement with a compression meter is influenced by many accompanying factors (the same starter), it is better to check the condition of the cylinder-piston group with a pneumatic tester. A leak test will provide the most accurate information about the condition of the internal combustion engine.

Starting system

Charging mode with a working generator

Since diesel fuel must be compressed quite strongly to start, diesel a priori has a reinforced starter. To start in cold winter, the starter requires much longer endurance from the battery. Of course, sufficient current is required for starting. If the starter on your car is working properly, the problem of poor starting in cold weather may be insufficient starting current.

For diagnostics:

• check the degree of charge in each section of the battery (the value for a working battery, approximately 80% charged, is not lower than 12.4) and the electrolyte density value (respectively, 1.233);
• oxidation of contacts on the starter, battery terminals or ground will not be able to pass sufficient current to the starter.

ECU Common systems Rail will not even give a command to open the injectors if the starter cannot provide the threshold fuel pressure in the fuel rail.

You can measure the pressure in the rail using a computer diagnostic equipment and related software.

Air

A diesel engine cannot function properly if there is air in the fuel line. Due to air after inactivity, the pressure in the fuel line drops. Before starting the internal combustion engine, the starter will spin, building up pressure in the line. The main symptom of such a malfunction will be difficult starting after inactivity. Subsequent launches and general work the engine may not undergo any changes.

A manual fuel pump will make it much easier to vent the system.

Diagnostics:

• It is necessary to insert a short transparent tube into the low pressure fuel line (preferably in front of the injection pump). This will help you detect any air bubbles;
• Use a compressor to pump about 2 atm of pressure into the tank. All areas of damage to the hose, suction in places of seals will begin to “sweat”.
• When starting, look at the exhaust. If the engine does not start, but at least smokes (black smoke is the remains of unburned fuel), the problem is most likely not in the system.

To the most common reasons air leaks include damage to the fuel line hoses (supply and return), loss of elasticity sealing rubber bands, rings, seals (for example, fuel filter, drive shaft or fuel injection pump covers). The last problem most typical in cold weather, when rubber products are deformed under the influence of temperature.

If a diesel engine starts after being idle, but stalls after a while, the reason may also be hidden in the air. It’s just that the design of the fuel injection pump ensures a small amount of diesel remains, even if all the fuel has escaped from the return line back into the tank.

If the engine stalls after sharp pressing on the pedal, and then immediately releasing the gas, 99% the problem is suction.

Glow plugs

If the engine starts poorly in cold weather, especially in the cold in winter, but does not stall, the first step is to check the glow plugs and the pre-heating system as a whole. Starting from +5, even a generally serviceable diesel engine with an inoperative air heating system in the combustion chamber will have difficulty starting. The system includes:

• glow plugs;
• heating relay;
• a bus that connects all spark plugs into a single circuit.

The check should begin with the glow plugs. I can assure you that the popular test method of measuring resistance with a multimeter is a largely ineffective test. It is designed to detect a rupture of the heating element (in this case there will be no resistance). All spark plugs may have resistance, but the cause of poor starting is cold winter will be in them. At high temperature overboard or when hot, a serviceable diesel engine can be started without glow plugs at all.

In severe frost, the purpose of the system is preheating not only in making it easier to start, but also in helping during the first seconds of warming up. After the “spiral” fades to dashboard, the candles continue to work for some time. If you managed to start the internal combustion engine on a frosty morning, albeit off the air, but the engine continues to run unstably for some time, be sure to pay attention to diagnosing the glow plugs.

How to check

Only such a system will ensure proper starting in cold weather. Only the tip of the spark plug is in the combustion chamber. Therefore, a spark plug that shows resistance when tested may not be hot at the base and cause poor starting in winter.

All candles should heat up at approximately the same rate. If the engine does not start well after cooling, and after starting it smokes for a few seconds and runs unstably, you can safely start diagnostics with spark plugs.

It's also worth checking the relay. Perhaps due to oxidation of the contacts, it is not possible to transmit sufficient current for heating. Be aware of the possibility of a blown fuse or damaged tire. The warm-up time before starting depends on the coolant temperature. IN extreme cases causes incorrect operation systems can be hidden in the corresponding sensor.

Fuel

Domestic fuel at many gas stations is getting better. Especially in cold weather, when waxing the fuel immobilizes diesel engines. For your own good, we will ask gas station employees to present a fuel quality certificate. If, after refueling at an untested gas station, the engine is difficult to start, it stalls, smokes or runs erratically - most likely there is a problem with the fuel. Only after self-check you can be sure not only that the engine will start after an overnight stay and will not freeze when driving along the highway in severe frost.

Pressure, fuel portion and injection time

Part of the low-pressure circuit is the booster section in the fuel injection pump housing (an analogue of a gasoline fuel pump in the tank can additionally be installed). A malfunction of the booster system will result in the starter being forced to build up pressure each time.

The cause of poor starting, the fact that the internal combustion engine stalls, may be the fuel injection pump regulator.

Incorrect OZ leads to uneven operation, poor starting, the engine smokes or even stalls in some operating ranges. Symptoms can appear both when hot and before reaching operating temperature.

Injectors

The shamelessly “pouring” injectors add to the reasons for poor cold starting. Diagnostics:

• disconnect the return hoses. Attach hoses instead equal length, at the end of which attach ordinary syringes;
• start the internal combustion engine. Serviceable injectors should discharge an equal amount of fuel into the return line. If there is a significant scatter among the injectors, a bench test and replacement are necessary. faulty elements. Perhaps you'll get away with just sprays.

At the same time, on hot engine It starts normally, does not stall, but smokes more than usual due to the over-enrichment of the mixture. On the cold side, smoke will come out of the exhaust pipe (fuel droplets that have not turned into “fog”, which therefore did not burn).

Hot problems

If a heated diesel engine smokes and sometimes stalls, the owner should be mentally prepared for expensive repairs.

The primary cause may be the plunger. When hot, the fuel becomes “thinner”, which makes it difficult to build up pressure. If you notice that a warm engine loses traction and also has difficulty starting, you may not be able to solve the problem yourself.

Any owner of a car with a diesel engine may encounter the problem that the engine will not start. Or it starts, but immediately stalls. Or it clearly does not work in the mode in which it should function. The reasons for such problems with a diesel engine can be very different.

Understanding why a diesel engine does not start and eliminating the reasons for this engine behavior is sometimes quite difficult without the proper qualifications and experience. But today we will try to answer the question of why a diesel engine does not start.

How does a diesel engine work?

Unlike gasoline engines, where a ready-made mixture of gasoline and air enters the cylinders, in diesel engines the fuel is supplied separately and the air separately. Fuel entering the cylinders of a diesel engine ignites as a result high blood pressure, which is the main cause of the outbreak diesel fuel.

Fuel is supplied inside the cylinder through nozzles that spray the fuel into fine dust. And thanks to this, uniform combustion of the fuel occurs.

In addition, the fuel entering the cylinders is additionally heated by the glow plugs that diesel engines are equipped with.

However, it should be understood that under certain conditions the diesel engine may start even when faulty spark plugs glow or failure of the relay that controls the heating of the spark plugs. Plugs essentially make it easier to start the engine, and in some diesel models they continue to heat the fuel until the coolant temperature reaches a certain level.

Thus, it is clear that diesel engines have a lot various systems, and the reasons why a diesel engine does not start are quite varied.

Reasons why a diesel engine may not start

Compression in cylinders

The most common reason for a diesel engine not to start is a drop in compression in the engine cylinders. In this case, the fuel mixture does not heat up enough and it does not ignite.

In some cases, the reason for the lack of the required compression in the cylinders is wear of the cylinders and o-rings on cylinders. Such a breakdown can only be eliminated as a result of overhaul engine.

Sometimes problems occur in only one cylinder. In this case, the engine can start, but after this shock loads and shaking of the engine and the entire car begin. Those. one cylinder either does not work at all or flashes inside the cylinder occur irregularly.

Glow plugs

The next reason why a diesel engine does not start may lie in certain breakdowns in the glow plug system. Moreover, what’s interesting is that if the engine is warm, or the weather is warm outside, the problem with the glow plugs may go unnoticed. If the spark plugs do not work, then the internal space in the cylinder does not heat up.

If the engine does start when the spark plugs are not working, then problems may appear further, as the engine will run intermittently. It becomes more difficult if two or more glow plugs fail at once. There is practically no chance of starting the engine.

But the matter may not only be directly in the candles. A problem may also arise with the spark plug relay. If the relay works normally, then characteristic clicks are heard when starting, if, of course, you listen. It may fail and the electronic unit candle control. In this case, clicks are not heard. But if the engine is warm, it can still start. But if the air temperature outside is low, if there are problems with the glow plugs or with other components of this system, there can be no talk of any starting.

Fuel system

Another problem when starting a diesel engine can occur if there is a problem in the fuel system. For example, the fuel injectors are clogged. However, if during startup the starter rotates all the parts, but blue smoke appears from the exhaust pipe, this should mean that there is fuel supply to the cylinders. But the fuel ignition does not occur due to compression problems or due to problems with the spark plugs.

You can try to correct the compression by pouring a little oil into the cylinders. But this is just a temporary measure. And as soon as the oil is squeezed out or burned, the problem will appear with new strength.

Checking the injectors for clogging is a procedure that requires unscrewing all the injectors and then checking them on a bench. It may happen that the injector is not completely clogged and partially sprays fuel. In this case, the engine may sneeze and puff when starting. And in the exhaust it will be observed dark smoke from unburned fuel. Those. It turns out that the fuel is atomized incorrectly and some of the fuel simply does not burn.

If the starter turns, but there are no flashes in the engine, i.e. the engine is missing and no blue smoke, this means that no fuel is entering the cylinders. And here you need to check the entire fuel supply system, starting from the high-pressure fuel pump to each injector individually. However, the belt from the injection pump drive may simply fall off or simply break.

Problems in cold weather

If a diesel engine does not start in cold weather, then reasons related to the waxing of diesel fuel may be at play. Paraffins, which are contained in diesel fuel in a dissolved state, begin to thicken under the influence of low temperatures and clog the fuel filter. As a result, the fuel supply is completely stopped.

Other reasons

In addition, a problem with fuel supply can be caused by problems with the fuel line. Not only can it freeze in cold weather, but it can also lose its seal somewhere at the joints. Or a crack forms in the fuel lines.

One point should be understood - there is any smoke from the exhaust pipe at the time of start-up, which means fuel is being supplied. No smoke - a problem with the supply of fuel to the cylinders. Even this fact makes it possible to determine at least the direction of searching for engine failure.

In addition, there may be problems with the starter, which are manifested by characteristic silence after turning the key in the starter. Or just the clicking of a relay. So there are a lot of possible breakdowns.