One of the significant differences between diesel engines and gasoline engines is difficult conditions launch at low temperatures, due to the principle of its operation. Glow plugs should ensure a confident start of the engine, but if they fail, the driver will face serious problems.
Purpose and design
The fuel-air mixture in the cylinders of a diesel engine ignites at a temperature of 800-850 degrees. But in a cold diesel engine (less than 50-60 degrees), such a temperature cannot be achieved by air compression by pistons alone. That is why glow plugs were introduced into the design of this type of engine, working part which are located in the combustion chamber to heat the air.
The main task of the glow plug is to achieve, after turning the ignition key to the first position, as quickly as possible operating temperature to heat the air in the combustion chamber. The plugs heat up to 850-1300 degrees within 2-30 seconds and on average consume a current of 8-16 amperes (i.e. 96-192 W) each. The duration of the current supply to the spark plug and the voltage level are controlled by a relay or a special electronic unit. Having “turned off” the light on the dashboard, which prohibits the driver from turning on the starter, the relay continues to heat the spark plugs for some time - up to 3 minutes - with the engine running. However, some modern spark plugs are disconnected from the network immediately after the starter is turned off, since they remain hot for the time required to warm up the engine. In the most advanced designs, the electronics monitor the engine temperature, and if it recognizes it as warm enough, it does not turn on the spark plugs at all.
A glow plug is reinforced in a housing and covered with a casing a heating element. In the simplest case, it is a spiral of refractory metal. More complex candles have two spirals of different materials. By changing their resistance depending on the degree of heating, they provide automatic maintenance temperature and avoid overheating without the help of an external relay.
Symptoms of the problem
In a modern diesel engine, a working spark plug with a normally functioning control unit warms up to operating temperature in a few seconds.
Lack of heating of the internal volume of the cylinders is the most probable cause Difficulty starting a diesel engine. A working engine should start immediately after turning on the starter, from the first revolutions of the crankshaft. In warm weather, the failure of one spark plug is not always noticeable at start-up, but in the first minutes after start-up, some engines (depending on the model and condition) will run unevenly, since the combustion process in a cold cylinder is disrupted. Two problem spark plugs already seriously complicate starting. Failure of three or four spark plugs at once is unlikely, so if the engine does not start, the reason may lie in the control relay or wiring. There are cars in which a lamp on the dashboard indicates a faulty spark plug.
With faulty spark plugs, a warm (60 degrees and above) diesel starts without problems.
Causes of problems
The nozzle should not “pour” diesel fuel in one stream directly onto the spark plug.
The spark plug fails for two reasons: the life of the spiral is exhausted (approximately after 50-75 thousand kilometers), or the fuel equipment is faulty. If one spark plug fails on an old car, the others also need to be changed - they will soon fail anyway.
The life of a spark plug is shortened by faulty fuel equipment, for example, a dirty or worn nozzle that directs a powerful jet of fuel directly to the working element of the heater. This causes a hole to form in the heater shell, and the spiral is destroyed. Finally, the spark plug is easy to break if installed improperly. Long candles Many modern engines break during dismantling because they stick to the block head.
A faulty control relay can cause the spark plugs to overheat - their shell is deformed, melts, and the spiral burns out. The relay itself can also “burn out”, and the wires coming from it can break or fray due to improper installation after repair.
Diagnostics
An extinguished warning light will indicate that the spark plug is warmed up and you can turn on the starter.
The simplest diagnosis of glow plugs is to check their electrical conductivity. The spiral must conduct current, its resistance in a cold state is in the range of 0.6-4.0 Ohms. If you have access to the candles, you can “ring” them yourself: not every household tester is able to measure such a low resistance, but any device will show the presence of a heater break (the resistance is infinity).
More accurate diagnostics, tracking the characteristics of each spiral, are carried out by specialists. If you have a non-contact (induction) ammeter, you can do without removing the spark plug from the engine. But it is often necessary to check the unit on a special stand and visually inspect the working part, which may show signs of overheating - melting, deformation of the tip, even to the point of its destruction.
In some cases - including if all spark plugs fail at once - it may be necessary to check the vehicle's electrical equipment. Namely, the spark plug control relay and its circuits.
Igor Shirokun
Photo Bosch, Beru
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Owners diesel cars Information on how to check glow plugs will be very useful, since they are an integral element of a diesel engine, and any failure in their operation will create discomfort or even force you to switch to public transport.
Replacing glow plugs - is it so important to do it on time?
The main function of these parts is to start the engine, because, as you know, its operating principle is somewhat different from gasoline, since the fuel in this case is ignited not by a spark, but by compression. And high temperature promotes more efficient ignition, which is what glow plugs provide. Modern cars are equipped with types that heat the fuel not only before starting, but also for several minutes afterwards, thanks to this the engine operates at idle speed becomes more stable, and the emission harmful substances reaches a minimum due to more efficient fuel combustion.
Undoubtedly, in the warm season there is practically no need for them, but as soon as the temperature environment reaches +5 °C, it becomes almost impossible to start a car without this element. Therefore, it is very important to monitor their condition, especially with the onset of cold weather, and for this you need to know how to check the glow plug. But first, let’s take a closer look at their connection diagram in order to understand at what point you need to sound the alarm.
Glow plug connection diagram and signs of malfunction
In principle, they can be compared to an electric heater. The spark plug rod is located in the pre-chamber in such a way that its tip is located directly on the border of the vortex of the working mixture created by the nozzle. The glow plug connection diagram ensures automatic supply electric current, immediately after turning the ignition key to the operating position. They heat up very hot high temperature and, accordingly, warm up the combustion chamber, as well as the air entering it.
The glow plug control unit is responsible for their proper functioning. The algorithm for its operation is as follows: after turning the key, the spark plugs are connected directly to the battery, at the same time the corresponding light on the instrument panel lights up, after some preheating time this light goes out, which indicates that the engine is completely ready to start.
The first sign that there is a failure in the electric heating system is a non-working indicator. This may indicate a failed fuse or temperature sensor. If the indicator burns for a long time, it indicates the need to replace the thermal switch, and if this is ignored, the thermal pin may burn out, and then the incandescent will be needed. True, the indicator sometimes may not signal a possible breakdown.
Also a clear sign The fact that some spark plug starts to “become naughty” means that the engine is starting to be problematic. And in this case, checking the glow plugs is urgently necessary.
How to check glow plugs yourself?
You can do the diagnostics either at a service station or on your own; for this you only need a clamp-on ammeter. You must proceed as follows. The first to be disconnected is the supply drive going to the positive contact of a particular spark plug; this drive must be connected to the “plus” of the ammeter. The second pole of the ammeter is connected to the positive contact of the spark plugs themselves. The system turns on and the current strength is determined. Since each participant in the motor operation consumes approximately 12 A, therefore the total should be 48 A; if this value is less, then there is a malfunction.
There is another way to check the glow plugs in an inverted state. The removed spark plugs should be installed on a common bus, ends up, and using wires large section of the housing, each of them is connected to ground. Then, their condition is visually determined (a spark that appears will indicate a malfunction). Using a multimeter or other specialized instruments, you can check the resistance of the glow plugs; it should be less than 5 ohms, but if its value approaches infinity, then the heating coil is faulty.
Almost every driver knows that a diesel engine does not have an ignition system like a gasoline internal combustion engine. Then the question arises of how a diesel engine starts. The answer to this question is quite simple. In order to ignite a diesel fuel mixture, it requires compression, not a spark.
The principle of operation is based on the fact that the air is heated due to strong compression, and when fuel enters it, it ignites. The problem with such a motor is that in the cold season, in order to heat the air in the cylinders, external heat is also required. It is worth noting that in diesel engine there are no spark plugs, but there are glow plugs.
Chamber heating
As everyone already knows, a gasoline engine has spark plugs. The ignition process is simple. The spark plug produces a spark that ignites the gasoline. Solara ( diesel fuel) does not ignite from a light spark, so it was invented so that the diesel would go straight into hot air and ignited.
The main work of a glow plug occurs in the cold season. The fact is that it heats up both the fuel and the air that enters the cylinders for compression. It really helps to start a diesel engine in the cold season.
There are two types of glow plugs.
- The first type is a body with a monolithic spiral. This system is simpler and more profitable for the buyer. This system is installed on most diesel vehicles. This type of spark plug is much easier to adjust than a double coil plug.
- There is also a second type - the double helix. This type allows you to more carefully select optimal level and temperature, however, it is worth noting that for correct adjustment it is necessary to choose a high-quality spiral material, because if the spiral is made of low-quality material, it will quickly deteriorate.
Location
Almost everyone knows where the spark plugs are located, but the glow plugs are located depending on what brand of engine it is.
If a diesel engine consists of one auxiliary combustion chamber, then it is installed directly in this combustion chamber. If it is divided into cylinders, then it is installed in a pre-chamber or vortex chamber.
Modern engines have direct fuel injection, which means that swirl chambers are no longer installed. The glow plugs heat the cylinder itself directly.
Principle of operation
Unlike conventional spark plugs, it ignites the fuel not with a spark, but with the help of a heating coil. The glow plug is started by turning the ignition key. At this time on dashboard All relevant indicators about its operation light up. They start only to warm up to operating temperature, which happens in less than 4 seconds.
It is worth noting the fact that if the glow plugs are faulty, then it will be possible to start a diesel car only with a properly functioning starter. After the engine has been successfully started, electricity is still supplied to the glow plug for some time. This is necessary so that the diesel engine burns out completely without any residue. Complete combustion of the fuel ensures a quiet start of the engine, and also reduces the amount of harmful emissions into the atmosphere.
Advantages and disadvantages
A diesel engine, like any other, has its drawbacks.
- The main one is that in winter the car takes a long time to warm up, which is why the speed qualities of the car are lost.
- The second disadvantage is the difficulty of starting the engine in winter. That's where the cons end.
- One of the disadvantages is the fact that in order to refuel the car’s tank, you will need to choose the “right” fuel, especially in winter. The fact is that diesel can be used in summer, winter and off-season.
It is worth noting that all the disadvantages of diesel appear only in winter time, since without glow, many diesel engines will not start.
- Positive aspects include low fuel consumption, which is already cheaper than gasoline.
- The second advantage is the durability and endurance of the diesel engine.
- There is one more plus, but buyers rarely pay attention to it. This means that a diesel engine is environmentally cleaner than its gasoline counterpart.
Controversy
Drivers who drive gasoline and diesel constantly argue among themselves. The fact is that each engine has its own positive and negative sides. Every driver is firmly convinced that his engine is better. But in order to determine which engine is better for each driver separately, you can only drive both.
Summary
Each interested person, after reading this article, will be able to draw several conclusions for himself: important facts. Many people did not know that a diesel engine does not have an ignition system, and now they understand why owners of diesel cars often tinker with the hood of their cars in winter.
The article also describes the pros and cons of such an engine, and how such a low level of environmental pollution is achieved.
A glow plug is a special element of a diesel engine designed to bring the injected fuel to desired temperature at . In addition, they are used in the engine pre-heating system in carburetor engines and to start autonomous heating of the car interior.
According to the principle of operation, they are completely different from, since they do not create a spark during operation, and bringing the fuel to the required temperature is ensured by heating the glow plug relay.
Since combustion is achieved by providing a certain pressure, glow plugs are part of the pre-start device. In fact, their operation is limited to cold diesel starts at temperatures below 5°C. As a result, many modern types engines without prechambers do without this part altogether.
Another method to get rid of spark plug installations is widely used by Cummins. They build special heating grids into their diesel engines. However, the use of these parts is unlikely to be limited in the near future, as in the future it is planned to increasingly drive motors with low level compression, and their cold start without special means practically impossible.
Where are these spark plugs installed?
The installation locations of glow plugs directly depend on the design of a particular engine.
With a separate combustion chamber, they are located in a vortex chamber or prechamber. If a diesel engine uses an undivided combustion chamber, then they are installed in it.
Glow plug installation locations
Glow plug design
Structurally, the glow plug is an electric heater with a spiral relay immersed in containment. Based on the materials, they are divided into two types: metal and ceramic.
Glow plug device
In addition, there are so-called turbo spark plugs. They have a different body shape with a conical tip. Due to this, it is possible to reduce leaks. These spark plugs are mainly used in racing cars.
By design, glow plugs are distinguished between mono-spiral and double-helix. The former are easier to manufacture and are installed on most modern cars. Due to the use of only one spiral, they are easier to configure for self-regulation and the required temperature. This design is more reliable and stable over time.
On the other hand, double-coil glow plugs allow you to better regulate the optimal temperature balance. True, to create them, you need to carefully approach the process of selecting materials, since if the material is not suitable, they can work unstably and collapse. The double helix is now just being introduced into mass use, but it is the future.
Principle of operation
The glow plug block comes into operation automatically when the ignition key is turned before the starter starts. At the same time, special indicators light up on the instrument panel in the cabin, signaling its operation.
Working principle of a glow plug
After the operating temperature has been established, the indicators in the cabin go out, but the voltage is still supplied for some time.
The main function of glow plugs is to warm up the injected diesel fuel during engine starting. If they are faulty, ignition of the fuel is difficult and is possible only after prolonged rotation of the starter. In fact, they allow you to start a diesel engine in frosty weather with the same success as in hot weather.
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In modern engines, glow plugs perform another important function. They continue to be supplied with electricity for several minutes after a successful start to stabilize operation and ensure complete combustion of the fuel in the chambers.
Thus, the amount of harmful emissions into the atmosphere from incompletely burned diesel is limited. In addition, by ensuring complete combustion of fuel, the noise level when starting the engine is reduced.
A diesel engine has some differences from the operation of a gasoline engine. After all, the explosion of the mixture there occurs not from a spark, but from compression of the air-fuel mixture. However, there are still spark plugs in a diesel engine, but they are intended to heat the combustion chamber in winter period. We will analyze the malfunctions of glow plugs, their diagnosis, and also tell you how to replace them.
Working principle of glow plugs
The principle of operation of glow plugs is that they heat the air in the combustion chamber to a temperature of 1000 degrees Celsius. Warming up is carried out until it reaches 70-80 degrees. All glow plugs are divided into two types - ceramic and pin.
Any glow plug consists of a small number of elements. This is the head unit (housing) and the filament, which consists of two special resistors. The first resistor is constant and has a constant resistance, and the second is a resistance with an adjustable temperature coefficient. As the engine temperature increases, the temperature of the spark plug also changes, which makes heating more efficient and economical in relation to the battery.
Diagnostics of spark plugs on diesel engines
Glow plugs must be checked in a timely manner and, if necessary, replaced with new ones, since if at least one element fails, it will be impossible to start the engine. The frequency of replacement is always indicated by the engine manufacturer, but the spark plugs must be checked before each winter and, if faults are detected, the entire set must be changed.
There are only two ways to determine the health of glow plugs. The first involves the participation of two people.
Allows for self-diagnosis of elements. If one of the spark plugs breaks, the corresponding indicator on the dashboard will light up.
Video - How to check spark plugs with one wiring
Signs and causes of malfunctions
During the cold season, the fault can be determined directly. Firstly, with faulty spark plugs, the engine starts with great difficulty, and its operation is unstable. The second sign can be considered. Once you notice all of the above symptoms, you need to check the spark plugs. As a rule, if the engine does start, only one spark plug is faulty. In other cases - two or more.
Faulty spark plugs may be caused by improper operation of the fuel system, electrical wiring or control equipment. A separate case is when a candle has simply exhausted its service life and become unsuitable for use. If this happens ahead of schedule, you should look for and eliminate the cause before replacing the spark plug set.
Replacing glow plugs
Replacing glow plugs is not difficult.
Before starting work, open the hood and let the engine cool. Carrying out work on a warm engine is strictly prohibited.
Video - Removing spark plugs from diesel engines
Then a new one is installed in its place and screwed until it stops with little effort. This must be done with extreme caution, since the metal of the candles is quite fragile, and it can easily break. If this does happen, you will have to remove the cylinder head and drill a threaded hole for a new spark plug in the metal of the old one.
After this, reinstall the cable and try to pull it in different directions. If it doesn't fit securely enough, you haven't installed it correctly. Check the fastening and try again. The cable should fit tightly.
Do the same operations for the remaining glow plugs and connect the negative terminal of the battery. After checking the spark plugs, replace the insulation and close the hood. This completes the replacement of glow plugs. As you can see, it was quite easy.