Diesel glow plug test. Replacing glow plugs on a diesel engine

Function of glow plugs

A diesel engine differs from a carburetor engine in that it ignites automatically. Due to compression, the intake air is heated in the cylinders to a temperature of 700-900°C, which leads to self-ignition when fuel is injected. At the same time, a diesel engine requires higher compression (compression ratio 20-24) and, accordingly, a more durable structure than a carburetor engine. To ensure that the required temperature is achieved under unfavorable operating conditions, such as cold starts or frost, it is necessary to provide additional heating in the combustion chamber.

In this case, glow plugs fundamentally function as an immersion electric heater: electrical energy passes through a spiral resistor, which becomes very hot (up to 1000°C).

This simple principle, however, causes some difficulties in practice in terms of service life, protection against overheating and power consumption. In the 60s the startup process lasted up to 30 seconds. In the 80s The startup time has already decreased to 3-5 seconds. With the advent of turbocharged diesel engines, at ambient temperatures above 0°C there is practically no difference compared to a carburetor engine. Only at temperatures below 0°C is heating still required.

However, this is by no means the end of the development. Residual glow plugs are required. The glow plugs must come into action not only during the starting process, but also depending on the temperature for up to three minutes during the warm-up phase of the engine at idle speed. This is the only way to guarantee a high driving culture and low emissions from the very beginning. This inevitably places increased demands on the service life of glow plugs.

In addition, in the future, low-compression diesel engines will be used, which, due to high boost, provide high power with low emissions. However, this kind of concept has poor starting behavior due to its design. Here, some benefit can be obtained from high-temperature ceramic glow plugs, since they are significantly hotter than metal glow plugs and, in addition, have a longer service life.

Older types of engines are usually equipped with systems without additional glow after starting the engine. Modern types of engines are equipped with glow systems with additional glow after starting the engine.

Additional glow after engine starting has a direct effect on reducing the amount of smoke emitted by the engine, and also helps to comply with the strict EURO 2 and EURO 3 emission limits. The design of glow plugs with glow cores with improved self-regulating ability prevents thermal and current overloads of the glow plugs after engine starting, when the voltage in the vehicle network reaches almost 16 V, and also helps to extend the life of the glow plugs.

The use of the most optimal material for the filament spiral and, above all, the adjusting spiral, as well as the optimal shape of the working part of the filament core, makes it possible to quickly reach the operating temperature with a low level of power consumption throughout the entire filament time, as well as to eliminate the “peak” state of the electric current at the beginning of the process incandescent

Glow plugs with monocoil

They are designed for use with a single coil that provides both the glow and the self-regulating required to quickly reach the glow plug temperature and limit the maximum temperature while maintaining the required service life.

For most engines currently in service, this design meets the speed and reliability requirements of filament.

Due to engine innovations, mono-coil glow plugs are gradually being replaced by double-coil glow plugs, which have even better temperature control.

Only the design of a glow plug with a double spiral, when using optimal materials for the manufacture of the glow plug and adjustment, makes it possible to achieve the optimal temperature of the working part of the glow core in all modes of the engine starting phase, i.e. before starting the engine, during starting and shortly after starting the engine.

1. Regulating spiral. 2. Filament coil with self-regulating action. 3. Filament coil.

The working part of these glow plugs consists of an incandescent coil made of resistive material. When used for heavy fuel compression self-ignition engines with a swirl chamber or pre-chamber, they are positioned and operate in the same way as glow plugs with a filament core. Currently, they are mainly used to facilitate the start of various types of heating units or to heat the air in the engine suction pipe.

Examples of glow plug placement in an engine

Checking the glow plugs

For a diesel engine, winter begins when the thermometer drops to + 5°C. Only up to this air temperature is it possible to somehow start a diesel engine with non-working glow plugs. At lower temperatures this is impossible, even if only one spark plug is acting up.

So, glow plugs must provide the combustion chamber with the temperature necessary for normal mixture formation and self-ignition. It must be said that the spark plugs cope with their task quite effectively, especially on vortex and pre-chamber diesel engines.

The operation of the glow plugs is “signaled” by an indicator on the instrument panel, which should light up and go out after a while, as if indicating that the air in the combustion chamber is ready to receive a portion of diesel fuel. Experience shows that you should not trust this indicator. It can light up even if the fuse has blown and the spark plug control unit relay has not activated.

You can check the spark plug without removing it from the engine using a conventional tester:
To do this, you need to set the tester to resistance measurement mode;
Connect one terminal of the tester to the vehicle ground, the second to the spark plug terminal.
Lack of contact means the spark plug is faulty. It should be replaced.

Checking the removed spark plug:
Apply voltage from the battery positive to the spark plug terminal, and the spark plug body to ground.
With a working spark plug, the glow tube heats up immediately. After 10 seconds it becomes hot and begins to glow, otherwise the candle should be replaced.

While glow plugs on passenger diesel engines are found everywhere, more efficient pre-heaters that are so necessary in winter are extremely rare. And this is understandable, because most diesel foreign cars are designed for the climate of Central Europe and are absolutely not adapted to our winters. Cars from Scandinavia, as well as German and French ones, aimed at our market, are much better prepared for operation in winter conditions and have a number of “highlights” in their design in this regard, including pre-heaters. They may be installed at an additional cost, but when paired with a timer, such a heater works wonders - the car “comes to life” as if an alarm clock rings. When the owner arrives, everything is ready for the trip: the engine is warm, the interior is warm, there is no need to scrape ice off the windows, etc.

Spark plugs in a diesel engine ensure guaranteed starting of the power unit when cold. The principle of their operation is to bring fuel under high pressure to the required temperature using a special relay. A diesel engine has as many spark plugs as there are cylinders in it. There is one spark plug for each engine cylinder.

The principle of switching on a diesel engine

The fuel-air mixture, which is under pressure in the cylinder, is heated to 900°C. To ensure fire conditions, the structure is highly durable. The combustible mixture is ignited by the compression ratio, and not by the spark plug. At ambient temperatures below plus 5°C, down to severe frosts, the combustion chamber requires forced heating using ceramic or pin glow plugs.

The glow plug in a diesel engine is capable of heating the injection zone to 1000°C in a matter of seconds. When the diesel engine is turned on, these devices operate until the coolant temperature reaches plus 75°C.

Due to the increased demands of environmentalists, thanks to their unique properties, spark plugs begin to function at idle speed. The design of these parts helps reduce the amount of harmful emissions from a diesel engine into the atmosphere.

Design features of various types of candles

These structures can be made of either closed ceramics or open metal. The heating element is made in the form of a spiral.

Metal pin structures have spirals: heating and adjustment. Thanks to the first, rapid heating occurs, the second serves to protect the structure from overheating.

The composition of ceramic parts is more complex:

Metal body.
Heating tube.
Connecting bolt and nut.
Adjustment spiral.
Ceramic filling.
Central electrode.
Threaded part.

Ceramic parts are preferred due to their ability to produce heat quickly and provide very high temperatures.

Under the influence of electric current, the coil heats up. The high temperature in the motor prevents the element from heating above 850°C; heating lasts for a short time: from 4 seconds to 2 minutes. The duration of heating is monitored by an electronic control unit, which monitors the temperature of the coolant through special sensors.

While heating continues, the control light located on the instrument panel lights up. Turning off the lamp indicates that the engine is completely ready to start.

The glow plugs continue to work after the engine is turned on, continuing to warm up and ensuring the most complete combustion of the air-fuel mixture, reducing harmful emissions.

Methods for checking spark plugs

You can check the voltage in the elements using a multimeter or car battery.

In order not to dismantle the device, just connect it to the battery. The connection diagram is as follows: the minus is connected to the spark plug body, and the plus to the terminal, respectively. In a working unit, the coil heats up within a few seconds. The absence of heat indicates the need to replace the device.

When checking the spark plugs in the injectors, you need to unscrew the elements and examine the glow of the pins, which should glow. A difference in the glow intensity of at least one element indicates the need for additional verification by measuring its resistance. In order to avoid rapid failure of the remaining elements, the entire set is replaced at once, regardless of how many parts turned out to be defective.

It rarely happens that more than two devices fail, in which case it is necessary to check the electrical wiring or electronic control unit.

Using a multimeter, the performance of a dismantled spark plug is determined by the “diagnosis” method.

In modern cars, these components can be checked through self-diagnosis, additionally using an indicator located on the instrument panel, which gives a signal when a spark plug breaks.

Description of signs of malfunctions of incandescent elements

Failures of glow plugs are manifested by the following defects:

The engine does not want to start.
Uneven operation of a cold engine.
The appearance of white exhaust gases.

If the car owner has recently replaced all the spark plugs, then the reason may lie in a malfunction of the element due to the fault of the manufacturer. The defective part must be unscrewed and replaced with a new copy. Malfunctions of incandescent elements are most noticeable in winter. A decrease in ambient temperature causes more signs of faulty filament elements to appear.

To facilitate the dismantling process, a special diesel engine glow plug puller is used. It must be used in conjunction with a tool adapted for a square or hexagonal head.

Why do spark plugs fail?

The service life of modern diesel glow plugs is 60 thousand kilometers, subject to operating conditions. If damage to the shell of the spiral occurs, the entire device will fail earlier, because dirt and moisture penetrate into the resulting crack, and the spiral closes to the housing. The shell may fail for the following reasons:

failure to observe thoroughness and accuracy when installing the glow element into the motor;
the appearance of electrochemical corrosion over a long period of time;
installation of spark plugs that do not correspond to the models of this type of diesel engine.

These devices are very important - they ensure both uninterrupted starting of a diesel engine at sub-zero ambient temperatures and significantly reduce the amount of exhaust harmful gases.

Many car enthusiasts are interested in the question of how to check glow plugs in a diesel engine, since it is not always possible to start the car in cold weather. And there are some nuances here. The fact is that with several faulty spark plugs, a diesel engine can still be started, but only at an outside temperature of +5 °C. If this indicator is lower, then the car will not start even with one faulty spark plug.

Often, because the car is not started, many drivers postpone planned activities or switch to public transport. Only in reality it is possible to check the performance of the candles without resorting to the help of specialists. There are three methods that have already been time-tested and will provide answers to many questions. But first, a little theory regarding the operating principle of these elements will not hurt.

How do glow plugs work?

To find out how to check the glow plugs in a diesel engine without removing them, you need to familiarize yourself with the operating principle of these elements. And they, unlike their analogues for gasoline engines, function somewhat differently. The same can be said about their appearance - nothing in common. And if in units running on gasoline, a spark from a spark plug ignites the working mixture, then in diesel engines the fuel ignites due to pressure.

But there is also one nuance here: if it’s cold outside, then what contributes to the entry of cold air into the working chamber. In this case, starting is difficult and the car needs to be warmed up. On older cars, the glow plugs come on every time the engine is started. In modern models they are not always activated, but only at negative temperatures.

The maximum temperature of the spark plug tip is 1350°C. There are two spirals inside it:

heating;
regulating.

With the first, everything is clear - it provides heating. The function of the latter is protective in nature, since it protects the spark plug from overheating as the temperature rises. This is done by increasing electrical resistance.

Varieties of candles

When deciding how to check the performance of glow plugs on a diesel engine, you need to know what types of them exist. they are available in two types:

ceramic;
pin.

The former have a tip made of ceramic, which withstands temperature changes. The protective shell is made of silicone nitrite. The heating of such a spark plug reaches 1000°C, and the engine starts without problems. Such parts are highly efficient and have a long service life.

For pin candles, the heating element is made of an alloy of iron, chromium and nickel, and the internal cavity is filled with magnesium oxide. This candle works at intervals from 4 seconds to 2 minutes.

Without a relay, nowhere

As you know, diesel fuel ignites under pressure as a result of strong compression in the combustion chamber. The relay supplies the required current, which heats the tip. The resulting heat heats the intake manifold, engine cylinders and working mixture to the desired temperature. Now it is easier for the fuel to ignite when under high pressure.

But before moving on to the question of how to check the glow plugs on a Nissan Pathfinder (diesel) or any other brand, it’s worth considering one more point. Often the mixture ignites before it even enters the cylinder. The result of this is that the efficiency of the engine decreases or it refuses to start at all. In order to ensure the required heating mode, a glow plug relay is used. Thanks to it, the electrical circuit closes and opens as needed. This ensures the optimal degree of heating of the working mixture.

The relay itself, of course, does not regulate the heating operation, since this is the prerogative of the ECU, which relies on the readings of the OX and crankshaft sensors. Thanks to commands from the block, the circuit is closed and opened.

Modern diesel engines have the option of additional heating when the engine is already running. This allows you to reduce the noise level during operation of the power unit, as well as minimize the amount of harmful emissions into the environment.

Characteristic symptoms

You should think about how to check glow plugs in a diesel engine if there are the following characteristic signs:

The engine can be started with great difficulty.
At idle speed, the power unit operates unevenly.
There is a white tint in the exhaust.

If the spark plugs were changed not so long ago, this may indicate a defect on the part of the manufacturer. Otherwise, you can be sure that one of the elements is faulty. In any case, it is necessary to carry out diagnostics by visiting a service station or doing everything yourself.

It is worth considering that problems with spark plugs manifest themselves well in the cold season (autumn or winter), while in summer it is quite difficult to determine the malfunction.

Diagnostic methods

Y is the weak link. It is this part that most often fails, and this can happen at the most inopportune moment. The consequences of such a malfunction will not take long to appear, especially in winter. In this case, you will not be able to start the car.

How to properly check glow plugs on a diesel engine? There are several ways:

Checking for spark.
Diagnostics with a multimeter.
A good method with a light bulb.

It is worth considering them in detail, which will allow you to determine what related tools may be needed.

Checking for spark

Diagnosing a glow plug using a battery will provide more accurate information regarding the performance of the element. Moreover, each detail is checked individually.

There is only one nuance here, which for some drivers may be a significant drawback. The point is that you need to unscrew all the spark plugs. This will take a lot of time, especially if you need to dismantle individual parts that block access to the spark plugs. Otherwise, there are no difficulties in solving the problem of how to check glow plugs in a diesel engine.

For diagnostics you will need an insulated wire 0.5-1.0 m long. The whole procedure is as follows:

One end of the wire is wound to the electrode of the spark plug (you must first remove part of the insulation from it).
The other end of the wire is applied to the negative terminal of the battery.
The spark plug body is connected to the positive contact of the battery.

The whole picture will become clear here: if the tip turns red by more than half, then this indicates the serviceability of the glow plug. Otherwise, there will be no heating at all or only the tip will turn red. This already means that the part can only be replaced.

Diagnostics with a multimeter

This method is good because there is no need to remove candles and other parts, since the necessary manipulations can be easily done on the spot. All you need is the testing device itself. In this case, you can check each spark plug separately or all at the same time, having previously connected them via a common bus.

How to check glow plugs on a diesel engine with a multimeter? The entire procedure can be carried out in one of three modes:

dialing;
resistance measurement;
current measurement.

To make a call you need:

Move the device regulator to the appropriate position, and place the device itself in a convenient place.
Disconnect the wire from the spark plug.
One probe of the device is applied to the spark plug body, and the other to its electrode.

The presence or absence of a break can be determined by the sound signal. If it is there, then everything is in order (there is no break). If there is no sound signal, then this indicates the presence of a break.

Resistance measurement

With this method, you can only identify a completely non-functioning spark plug. However, it is impossible to determine how well the heating element itself works. In this case, you can measure the resistance value with the same multimeter, you just need to know the rating of a specific spark plug. As a rule, if the part is intact, then the resistance should be 0.7-1.8 ohms. This is also an effective method of checking the glow plug in a diesel engine with a tester.

Often spark plugs fire with a high resistance value, which leads to a decrease in current consumption. In this case, the computer “thinks” that these elements have warmed up and turns them off.

Current measurement

A more reliable result can be obtained by measuring the current, and it is also not necessary to unscrew the spark plug. First you need to unfasten the power wire and connect the probe of the device. Fix the second probe with the spark plug electrode. Now all that remains is to turn on the ignition and observe the readings. If the part is working properly, then the display should show numbers in the range of 5-18 A.

It is worth noting that in the first second the values will jump to the limit, and after 3-4 seconds the current will stabilize. In this case, the reduction in data should be gradual, without sudden jerks.

All spark plugs are checked in this way; their readings should be identical. Otherwise, if the readings of one of the spark plugs are excellent, it is worth unscrewing it and assessing its condition visually.

Good method with a light bulb

How to check the glow plug in a diesel engine with a light bulb? Yes, and with its help you can also detect a malfunction. Any 21 W light source (side lights or brake lights) is suitable for this. Two pieces of wire are soldered to it (the length is chosen arbitrarily). After this, you can proceed directly to the diagnostic procedure.

First disconnect the power wire from the spark plug. Then touch one end of the lamp wire to the spark plug electrode, and connect the other end to the positive contact of the battery. The glow of the light bulb will indicate that there is no break. Thus, you need to check all the candles one by one.

If the light bulb lights up dimly or there is no light at all, then it is better to replace such a candle. This method also does not provide reliable diagnostics, since it is impossible to determine the degree of heating of the working rod.

Features of checking the spark plug relay

Many car enthusiasts are interested in one important point: how to check the glow plug relay on a diesel engine? The question is interesting and requires deserved attention.

Typically, such a device is triggered after each engine start. At the same time, you can hear a clearly audible click - this is how it turns on. If there are no sounds, you should think about diagnosing this element. However, it is worth finding it first.

This device looks like a box that is attached to the body of a car. The area of its fixation is usually called mass. To find the relay, just follow the wires coming from the glow plugs.

Each such device has several pairs of contacts. Single-component relays have 4, and two-component relays have 8. Two of them are removed from the coil winding, and the rest are control ones, which close when they receive a signal.

So how to check the glow plug relay on a diesel engine? In each car, the contacts are designated differently, but in most cases they are numbered as 85 and 86, and the control ones - 87, 30. To check, you can use a light bulb, which is connected to the winding contacts, after which voltage is applied to the relay. The serviceability of the device will be confirmed by the glow of the lamp.

Visual inspection of spark plugs

If diagnostic methods do not reveal the desired results or there are some doubts, a visual examination can be performed. This will allow you to determine the technical condition of the fuel system (including the piston group), as well as determine how correctly the electronic control works.

Therefore, each of the listed methods regarding how to check glow plugs in a diesel engine can, if necessary, be supported by a visual inspection. Obvious signs of a malfunction may include:

Tip melting.
A thick deposit is visible near the body.
The glow tube is swollen.

The presence of certain defects may indicate a number of factors. For example, cracks or swelling sometimes indicate that the voltage supplied to the spark plug is too high. In other cases, the element simply remains on for a long time.

As for melting, it can occur due to one of the reasons:

premature fuel injection;
nozzle contamination;
overheating, which, in turn, occurs due to late heating and weak compression;
Pressure valve malfunction.

During a visual inspection, you need to pay attention to the thin part of the candle. If there are melted areas on it, then it must be replaced, even if it is still working.

The considered methods of how to check the serviceability of glow plugs on a diesel engine can be applied both individually and in combination, which will even increase the chances of detecting a faulty product.

Allows you to raise the temperature in the cylinders before starting the power unit. In other words, due to the incandescent elements, the combustion chamber is preheated after turning the ignition key, as well as further maintaining the temperature until a certain warm-up of the engine. This is necessary due to the peculiarities of ignition of the fuel-air mixture in a diesel engine. In such engines, the mixture of air and diesel fuel ignites independently, and not from an external source (spark plug spark in gasoline analogues). Diesel fuel burns from heat due to strong compression.

We also recommend reading the article about. From this article you will learn about the features and criteria for selecting a battery for engines of this type, as well as why there are special requirements for a diesel battery compared to the selection of a battery for gasoline analogues.

For this reason, the ease of starting a diesel engine depends on the serviceability of the parts responsible for heating. Let us add that malfunction of glow plugs most often manifests itself at subzero temperatures. Next, we will look at simple and affordable methods that allow you to quickly check the glow plugs on a diesel engine with your own hands and determine the cause of difficulty starting a diesel engine.

Read in this article

Self-check of diesel engine glow plugs

As already mentioned, glow plugs ensure reliable starting of a diesel engine, which is especially necessary in cold weather. Conventionally, such a solution can be considered a kind of heater. On different models of diesel cars, such solutions may differ in the operating algorithm and general implementation scheme. One thing they have in common is the presence of a glow plug screwed into the block.

Early developments involve constant switching on of the glow plugs on a diesel engine in parallel with the ignition being turned on, that is, every time you try to start a diesel engine, the glow plugs heat up regardless of the current temperature. As for more “fresh” diesel engines, the glow may not be activated by the system if the engine is already warmed up or the ambient temperature is positive.

These features must be taken into account separately before checking the glow plugs. It will be necessary to separately find out under what conditions the elements for heating the combustion chamber are used on a specific diesel engine model. The inclusion of glow plugs is accompanied by the lighting of a separate indicator lamp, which displays a spiral pictogram on the dashboard inside the car. At the end of this solution for warming up the chamber on a diesel engine, the indicated light goes out.

It should be added that in the event of a malfunction of one or even a pair of glow plugs, the engine can start normally provided the temperatures outside are above zero. In other words, the warrior simply does not notice the malfunction. In winter, the situation changes, since starting a diesel engine with faulty glow plugs in cold weather becomes very difficult or even impossible.

In such situations, when the diesel engine does not start, the first thing you need to do is check the quality of the heating and combustion gauges. Glow plugs can be checked in the following ways:

connect glow plugs directly to the battery ();
evaluate the quality of spark formation on glow plugs;
check the glow plugs with a multimeter tester;

Checking glow plugs directly from the battery

To check the glow plugs by connecting them to the battery, they should be unscrewed from the engine. Note that for accurate diagnostics it becomes necessary to unscrew all installed elements. Also, in some cases, it will be necessary to dismantle certain components on the engine itself that do not allow easy access to the spark plugs. These nuances are a significant drawback of this verification method. Additionally, you will need a special tool, certain skills and free time.

Remember, you need to be very careful when unscrewing and tightening the glow plugs, as there is a risk of breaking off the glow plug. If the glow plug has broken off, then more serious repairs will be required to remove the remainder from the diesel engine block head.

The advantages of testing from a battery include the accuracy that this method provides. The condition and performance of the heating element are assessed separately and visually. This eliminates the possibility of installing parts that work but do not provide the proper degree of incandescence.

To diagnose the glow plug from the battery, you should take a wire with insulation about 50-60 cm long. Then the glow plug removed from the engine must be turned over so that the part on which heating occurs looks up. Afterwards, the glow plug is powered by the central electrode on the “plus” of the battery. Next, a piece of pre-prepared negative wire connects the battery to the side of the spark plug housing. The next step is to check the heating rate and its efficiency. Fast and full heating of the heating element is a sign of performance. Slow heating and/or partial heating of only the tip indicates the need for replacement.

Diagnosis of a glow plug based on the intensity of spark formation

Another way to check glow plugs on a diesel engine is to evaluate the intensity of spark formation after power is supplied from the battery. For such a test, an insulated wire is required (similar to the feather method). Then at the ends it is necessary to remove the insulator so as to expose 100-150 mm. wires.

Next, the power wires are removed from the glow plugs, after which the wire, stripped at the ends, is attached with one side to the positive terminal of the battery for testing. The other end must be passed over the central electrode of the element being tested to heat it up. Next you should pay attention to the following signs:

if the part is faulty, then there will be no sparking;
partial performance and low heat appear in the form of a weak spark;
on a fully operational element, the spark is strong, the sparking process is quite intense;

Checking the resistance of glow plugs with a multimeter tester

You can also check the glow plugs with a multimeter. This method requires less time and is the simplest. For diagnostics, you do not need to unscrew the glow plugs from the head. It is enough to disconnect the power wire from the central electrode of the spark plug being tested. Let us add that, structurally, the glow elements on a diesel engine can either have separate wires for each spark plug or be connected by one circuit.

It should also be noted that it will not be possible to simultaneously check the heating efficiency with a tester, which is considered a definite disadvantage. The fact is that a multimeter can show the serviceability of the element, but the combustion chamber will still be poorly heated.

To check glow plugs with a multimeter, switch the device to the “ohmmeter” operating mode. This is necessary to measure the resistance of the filament elements. To do this, the “+” tester probe is applied to the central electrode of the spark plug, and the negative terminal touches the side of the housing. The absence of readings on the device will indicate that the glow plug is faulty and requires replacement.

Before the onset of the cold season, the glow elements should be checked regardless of whether they are good or not.
Checking on a diesel engine by assessing the spark is recommended only for older cars. You should not test glow solutions using this method on a “fresh” model, which is equipped with a complex
If a malfunction is detected, it is optimal to replace the entire set, rather than one or two failed elements.
Try to purchase products from well-known manufacturers, since cheap solutions have a noticeably shorter service life and often demonstrate low efficiency of the heating element.

Finally, we would like to add that in order to reliably start a diesel engine in winter, it is necessary to select the right diesel fuel, fill it with high-quality diesel fuel according to the season, and, if necessary, use it. Also, in the case of diesel engines, it is advisable to install a diesel fuel pre-heater or.

Purpose of spark plugs in a diesel engine

So, the glow plug first heats the air in the cylinders until starting. Thus, it is almost impossible to start a diesel unit if the outside temperature is below 5 degrees above zero. These parts greatly increase the life of the motors. The engine does not bear such loads in the cold season.

But, after the engine starts and is sufficiently warmed up, the glow plugs for a diesel engine change their role. Now they help in fuel atomization processes. The whole point here is that diesel fuel, which is supplied to the cylinders through the injectors, directly collides with the spark plug. Thus, a vortex process is formed in the cylinder. Thanks to this, the formation of the fuel mixture is significantly improved.

Varieties and device

A diesel glow plug may be somewhat similar in appearance to a spark plug for gasoline engines. But at the same time, diesel analogues do not produce a spark. This part is equipped with a spiral metal or ceramic heating element.

The tip of the part, made of metal, can consist of several spirals. There are two of them. One of them is heating, the second is adjusting. The first spiral is necessary in order to ensure the fastest possible heating of the tip. The second, adjustment, is protection against overheating. The system works due to the resistance of the spiral, which increases with increasing temperature. This is a typical glow plug circuit.

There is space between the spirals. It must be filled with a special filler. It has good insulating properties. Here this filler performs several functions. This protects the coil from various influences, as well as more efficient heat transfer. A glow plug equipped with metal spirals can easily heat up to 1000 degrees.

Candles with ceramic heater

Such parts are similar in their operating principle. The difference in its design is that the spiral is enclosed in a shell made of ceramic materials. So, heating is carried out even faster, and the power will be even higher. For the part to heat up to a maximum temperature of 1350 degrees, one second is enough.

Glow plugs for diesel with one spiral

A part with this design is equipped with one spiral, which performs the heating and adjustment function, which is very necessary for almost instantaneous heating to operating temperatures.

In most diesel engines, this design fully meets all requirements, the part heats up quickly, and its service life is quite long.

The development of technology is gradually replacing such parts and replacing them with double-spiral structures. This is due to the fact that the double-spiral glow plug has better and more flexible temperature control capabilities.

Operating principle

Heating elements are located directly in the cylinders of diesel engines. They are located exactly where the turbulence of the fuel mixture takes place. When the driver of the car turns the key, voltage is applied to the spark plug. At this point it heats up very efficiently. The driver will see an indicator light on the dashboard of the car. It will take about 5 seconds for the heating element to heat up to operating temperatures. Naturally, this time depends on what the current air temperature is.

Next, the glow plug has already warmed up enough and works in order to sufficiently warm the cylinders themselves and the air in them. But this time is not enough to effectively warm up the cold cylinders. In addition, the air is constantly updated to the cold outside.

the main objective

The main purpose of this part is to heat the fuel to the evaporation temperature. Then the fuel will mix well with the air and immediately ignite, but from compression. After the corresponding indicator on the dashboard goes out, you can proceed to start the engine.

Glow plug relay

Naturally, these devices need to be managed. For this purpose, diesel cars have a special relay or a separate control unit. Both devices are necessary in order to regulate the voltage that will be supplied to the spark plugs. They also serve to regulate the temperature and duration of heating. The operation of this relay depends on the readings of the coolant temperature sensor and the crankshaft speed sensor. This is how the glow plugs in diesel engines are controlled.

Modern diesel units provide, in addition to warming up before starting, additional heating after the engine has been started. This function helps reduce noise when the diesel engine is running, and also allows you to significantly reduce harmful emissions into the atmosphere. Direct heating takes a few minutes. And it will stop if the coolant temperature reaches 30 degrees. Thus, the glow plug block affects the quality of operation and engine starting in cold weather and the service life.

Checking the operation of spark plugs on a diesel engine

Sometimes these parts can fail. In order to check the serviceability of spark plugs, there are several ways. This is done either with the direct help of a motor or without a motor at all.

To check without a motor, you will need some instruments. This is an ohmmeter or voltmeter. This way you can check the voltage status. If there are no devices, then you should use another method. For example, the spark plug being tested must be connected to the battery positive, and the negative to the cell body.

In a working candle, literally in a couple of seconds the spiral will heat up, and it itself will glow. If this does not happen, then the glow plugs need to be replaced.

Another way is to use a tire. To do this, you need to install the unscrewed parts on it. The ends of the candles must be directed upward. Next, using wires with a large cross-section, you need to close the mass by connecting the body of each spark plug.

Many instructions for repair and maintenance of motors write about a method for checking functionality through the holes for the injectors. Having unscrewed the nozzles, we observe the glow of the pins due to heating. If some don't light up as brightly as others or don't light up at all, then you can check the connections and resistance readings.

Relay test

How to check the glow plug relay? For this you will need a tester. To start checking you need to disable it. Now let's connect the tester to the terminals on the motor, as well as to ground. If there is no voltage, check the voltage supply from the battery.

Next, connect the tester to the opposite terminal. After that we start the car. Now we do the same as in the first case. If there is no voltage, then you need to check the high-voltage wire. Here the wire must be connected to the spark plugs. If everything works, then the relay needs to be replaced.

In addition, there is a way to test the relay using an ohmmeter. So. We check the resistance between terminals 30 and 87. Next, we apply voltage to terminals 85 and 86. If the relay does not work and the resistance is not zero, then the relay needs to be replaced.

The main reasons for spark plug failure

Typically, these parts can fail for two reasons. Either this is the end of its service life, or there is a problem with the car’s fuel system. It is worth knowing that if at least one spark plug fails, it is recommended to replace all of them completely.

As for fuel system malfunctions, if the injectors are worn or dirty, diesel fuel enters the heater. Then a hole is formed on the heater body and the spiral is destroyed. In addition, this part can be damaged during installation.

If all the spark plugs fail at once, then you need to diagnose the entire electrical part of the machine.

How to replace glow plugs?

These parts are located in the upper parts of the cylinder head. To replace, you need to disconnect the wires that are located under the head cover. Remove the wires connected directly to the spark plugs.

Then use a wrench to unscrew all the parts. You need to work carefully. After this, thoroughly clean the contacts, battery terminals, and spark plug wires. The holes into which the candles were screwed also need to be cleaned. You can use a scan for this.

After replacement, you should tighten the spark plugs, but not too much. If the tightening is tighter than necessary, the part may break during the next replacement. And this is already an expensive repair. But you shouldn’t tighten the part too loosely, as there is a risk that it will simply unscrew while moving. Now all that remains is to connect all the wires back. That's it, the replacement of diesel glow plugs has been successfully completed.

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