Everything about glow plugs for diesel engines

Purpose, principle of operation

So, glow plugs are designed to heat diesel fuel sprayed into the combustion chamber to the evaporation temperature, after which it mixes with air and ignites. This is only necessary at the very beginning of the movement (start and another 2-3 minutes), then the car warms up and the spark plugs turn off, because there is no longer any need for them.

The candle is placed in such a way as to fall into the flow of sprayed diesel fuel. The working part (a heating coil with or without a casing) protrudes into the combustion chamber and not only heats the incoming fuel to the desired temperature, but also creates additional turbulence in the vapor, which means it helps its distribution and combustion more evenly.

In most cars, glow plugs are turned on at any time of the year, and even in summer they make engine starting easier. In the newest models, the automatic system detects the engine temperature, and if it is already warmed up (coolant temperature 60°C or more), the spark plugs do not turn on.

Design

Basic design of a glow plug

Modern glow plugs are designed with one or two internal coils. The heating coil is made of metal with specified resistance values ​​and heats up depending on the current strength. The second spiral - the adjusting one - performs the function of automatically adjusting the current strength: the higher the temperature of the spiral, the higher the resistance value and the less current it passes to the heating coil. That is, with an increase in the temperature of the working part, the heating of the candle is automatically adjusted.

When the ignition is turned on, current is supplied to the terminal and from it to the central electrode. Next, the voltage is supplied to the adjusting and heating coils. The latter heats up, heating the tip of the candle to 1000°C in a few seconds. 3 minutes after starting the engine, the relay turns off the current supply to the spark plugs, and the engine runs as normal.

When the engine starts, the spark plug icon lights up on the instrument panel. While it is burning, the candle is warming up; when it goes out, you can go.

The shape and size of the spark plug depend on the engine model: in older cars with two-valve cylinders, there is enough space for the spark plug, which means it can be quite short and thick. Modern common rail engines with a four-valve design require different design solutions: the spark plug must be long and thin to take up less space.

Options for placing spark plugs in a diesel engine

Manufacturers offer the latest models of glow plugs with a working part diameter of only 3 mm. But along with the change in the shape of the candle, its strength also changes: long candles require extremely careful handling when removing and installing, since they break very easily.

And if... the glow plugs are faulty - autocenter.ua

One of the significant differences between diesel and gasoline engines is the difficult starting conditions 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.

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, the working part of which is located in the combustion chamber to heat the air.

The task of the glow plug is to reach operating temperature as quickly as possible after turning the ignition key to the first position in order 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 a heating element mounted in a housing and covered with a casing. In the simplest case, it is a spiral of refractory metal. More complex candles have two spirals made of different materials. By changing their resistance depending on the degree of heating, they provide automatic temperature maintenance 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 likely reason for 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.

Technical characteristics, design features

Glow plugs are constantly being improved: manufacturers are introducing new materials to reduce heating time and extend service life. As a result, from a fairly simple part with an open spiral, candles have turned into high-tech devices that meet the highest modern standards.

• Open and closed

Glow plugs were originally designed with an open coil, and such designs can still be found on some older vehicles. All modern candles are made closed: the spiral (one or two) is closed with a protective cap that protects them from burning out too quickly. Between the spiral and the body there is a heat-conducting powder, which allows heat to be transferred from the hot spiral to the tip in a short time.

Glow plug of open (a) and closed (b) type

• Number of poles

The candle can have one or two connection poles.

With a single-pole connection, the “plus” is supplied to the spark plug, and the “ground” is output to the housing.

Bipolar spark plugs have separate contacts at the top for “plus” and “minus”.

• Performance

Older spark plug models heat up to operating temperatures in 25-60 seconds. Modern fast-acting candles heat up in 10 seconds, and self-regulating ones - in 2-5 seconds. Achieving such a heating rate was made possible by the use of a regulating spiral, thanks to which the issue of burning out the heating element is eliminated, which means that more current can be used for instant heating.

• Material of manufacture

Glow plugs differ in the material used to make the working part.

Pin spark plugs have a metal shell made of a resistant alloy of iron, chromium and nickel. The heating coil is insulated from the body with heat-conducting powder (magnesium oxide), which, in addition to its insulating properties, also protects the coil from vibrations.

In ceramic candles, the heater is made of a refractory ceramic alloy that can withstand heating to maximum temperatures for a long time. The protective shell is made of silicon nitrite, a ceramic material with the highest thermal conductivity. Thanks to the design, the ceramic spark plug heats up to operating temperatures in a record time of 2 seconds, which allows you to start the engine immediately without waiting for warm-up time.

To comply with Euro-5 and Euro-6 standards, only ceramic spark plugs are suitable, which ensure optimal fuel combustion from the first second of start-up.

• Voltage consumption

Different manufacturers produce glow plugs designed for certain parameters of the vehicle's electrical system. As a result, the rated voltage may differ: from 6 to 24 V. Spark plugs with an afterglow function are installed complete with additional resistance: before starting the engine, heating occurs at maximum power, after starting the engine, the power is reduced to reduce the load on the adjusting spiral.

• Resistance

The resistance of the heating coil is 0.5-1.8 Ohm, depending on the type of candle (ceramic ones have less resistance, metal ones have more).

• Temperature and heating rate

The heating temperature of the working part is 1000-1350°C. For ceramic candles, this figure will always be higher, since the material of the heating coil suffers less from overheating.

The heating rate depends on the type of spark plug and the starting system.

Auto Glow and Self-Regulating Glow system - one relay that regulates pre-heating and warm-up after engine start depending on the coolant temperature. The candle heating speed is from 4 (metal) to 11 seconds (ceramic candles).

Super Quick Giow system - two relays, one for quickly heating the spark plugs before starting the engine (2-5 seconds, you can start the engine almost immediately), the second for constantly heating the spark plugs after starting.

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. Even if they are installed for an additional fee, but paired with a timer, such a heater works wonders - the car “comes to life”, as if an alarm clock is ringing. 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.

Resource and replacement

Glow plugs, unlike spark plugs for gasoline engines, do not have a clear replacement schedule. They are changed as they fail, on average once every 1-2 years. It is better to check and replace spark plugs in the fall, so as not to get an unpleasant surprise in the first frost.

The breakdown of one spark plug will have virtually no effect on the operation of the engine: it will start with the remaining three, and it will even start more or less normally with two non-working spark plugs, but only in the warm season.

The service life of the simplest spark plugs with a metal spiral is 50-80 thousand km, ceramic ones will last much longer - up to 160 thousand km, and some models of Japanese-made spark plugs - up to 240 thousand km.

Even if the check reveals that only one spark plug has failed, it is better to replace the entire set so that the service life of all spark plugs is exhausted evenly.

How to check glow plugs on a diesel engine? There's an answer!

Glow plugs are a very useful and necessary invention for owners of diesel engines.
Thanks to these heating devices, starting a diesel engine in winter occurs without any problems. However, even this, at first glance, “frost-resistant” invention often malfunctions or breaks down. Today in the “Useful Tips” section - glow plugs. In this article you will learn how to test glow plugs in three different ways.

Glow or glow plugs, or glow plugs, whichever suits you, are, as I already said, a very important invention. Thanks to these “miracle spark plugs”, starting a diesel engine in winter occurs without much difficulty, so to speak, “with a bang”

The task of the candles is quite banal and simple - heating the combustion chamber to facilitate the first start of the engine. Modern glow plugs are significantly different from their “ancestors”. The first glow plugs were activated every time the engine was started; modern analogues are able to analyze the ambient temperature and do not turn on unnecessarily (in summer, for example). Before checking the glow plugs, you need to clearly know the principle of operation of the spark plugs in your car, so that God forbid, working plugs are not “recorded” as non-working. As a rule, the inclusion of glow plugs is signaled by a special indicator in the form of a spiral on the instrument panel.

Methods for checking glow plugs1. Checking glow plugs using the battery.

This test method allows you to understand the cause of the malfunction of the heating elements. The principle is as follows: each glow plug is unscrewed and checked separately, and its external technical condition is analyzed, as well as its performance. The disadvantages include the need to unscrew the glow plugs; for some car models this is quite a big problem.

So, to check you will need a battery and a piece of wire half a meter long.

We take the glow plug, turn it over with the heating element facing up, then connect the central electrode of the spark plug to the “+” battery, and connect a piece of wire to the body of the spark plug and the “-” battery. If at the same time you see that the candle heats up quite quickly and evenly by more than half, you can conclude that the glow plug is in order. If the spark plug heats up slowly, or only the tip heats up, the spark plug is most likely faulty.

Video - how to check glow plugs on a diesel engine

https://youtube.com/watch?v=ixLCDINEwj0

2. The second method will require a multimeter or ohmmeter.

Turn on the device in the resistance testing position (ohmmeter). Disconnect the power supply to the glow plug. We connect the positive electrode of the multimeter to the central electrode of the glow plug, and connect the second negative electrode to the body of the glow plug. Let's look at what the device shows: if the needle moves and has not deviated from the zero mark by a single division, most likely there is a breakdown in the heating element. Such a breakdown can be treated by replacing the glow plug. The disadvantage of this testing method is that it allows you to detect only a completely “dead” glow plug; it will not be possible to detect a weak glow of the heating element using this method.

3. The third method is to check the “spark” of the glow plug or check for spark formation.

Yes, that’s not a typo, these spark plugs are also tested for spark. The method is old, but very effective, because it allows you to check the degree of sparking of glow plugs. To check, you need to have a piece of wire (half a meter to a meter), the ends of which will be stripped on both sides (remove 2-3 cm of insulation on each side). We remove the glow plugs and turn off the power. After this, we connect one end of the wire to the “+” of the battery, and with the other end we quickly make a tangential movement along the central electrode of the glow plug. In short, touch should be similar to striking matches on a matchbox. During the test, a working heating element should exhibit a strong spark. If the spark is weak, the glow plug heats up slightly and may soon fail completely. A completely “dead” glow plug will not produce any spark at all. The disadvantage of this test is that on new cars “stuffed” with electronics, this method can damage the ECU. Therefore, before checking the glow plugs for a spark, make sure that this method will not harm your car.

Video - how to check glow plugs for spark

https://youtube.com/watch?v=PP4aCPuPg44

Possible problems when replacing glow plugs

The origins of the problem lie in the geometry of the spark plug itself: a long and thin rod is easy to break, especially considering the tight fit of the spark plug in the spark plug well, where the gap between it and the spark plug is filled with combustion products and oxides. Masters call this situation “the candle is stuck.” Unscrewing a stuck spark plug is a task for an experienced technician, and even then there is a risk of breaking the spark plug if too much force is applied.

Unlike spark plugs, it is best to entrust the replacement to a good service station: in addition to tools and special materials (penetrating lubricant, for example), experience in such work is required. For comparison: replacing glow plugs will cost about 400 hryvnia, drilling out a broken spark plug will cost from 1500 and above (to infinity), depending on the complexity of the work.

Spark plug damage due to improper installation

When replacing spark plugs yourself, you need to consider several points:

• Replacing spark plugs must be carried out only on a warm engine and in a warm room (or during the warm season) so that the engine does not have time to cool down during operation. Accordingly, you only need to work with gloves to avoid burns;
• You need to unscrew a used spark plug just as carefully as screwing in a new one, taking your time and observing the torque. To facilitate the process, a special penetrating lubricant or synthetic motor oil is used;
• When unscrewing the spark plugs, try unscrewing each one one at a time. After all the attempts to increase the force on the key and again try to unscrew all the spark plugs one by one;
• Before installing new spark plugs, their seats are cleaned of carbon deposits;
• When installing, the spark plugs are not screwed in all the way! The tightening torque recommended by the manufacturer must be strictly observed.

What shortens the life of spark plugs?

Since there are no replacement regulations for glow plugs, their service life will largely depend on operating conditions. What shortens the “life” of candles:

• Incorrect installation. You need to be able to install a glow plug normally, and the slightest failure to comply with the technology (for example, working on a cold engine or incorrectly applying force to the key) can damage the glow plug even at the installation stage;
• Faulty or clogged fuel injector. Under normal conditions, the fuel is sprayed into a fine mist, with only a portion of it making contact with the spark plug tip. If the injector holes are clogged, diesel fuel will spray out, often directly onto the spark plug. Because of this, the tip quickly burns out and the spark plug fails;
• Installing an unsuitable spark plug (not designed for this type of engine or on-board voltage);
• Malfunction of adjacent components of the car, for example, engine oil getting on the spark plug due to engine wear, malfunction of the injection control system, malfunction of the computer;
• Carbon deposits around the spark plug can create a short to ground, which quickly damages the spark plug. To avoid short-circuiting on new spark plugs, before installing them, technicians clean the spark plug socket from carbon deposits using a special reamer.

When replacing spark plugs, you need to pay attention to the condition of the used ones: their condition may indicate problems in the engine operating system:

• A swollen tip usually indicates overheating due to excessive tension on the heating coil or engine oil getting on the spark plug;
• A damaged or broken tip indicates a malfunction of the fuel injection system (clogged injectors or poor synchronization of the system);
• Damage to the contact rod (at the top) and movement of the tip relative to the body indicate incorrect installation (tightening too tightly).

Checking the glow plugs

The main damage to the candle itself is damage to the heating coil. You can check the performance of the spark plugs yourself, without even removing them from the engine. To do this, you will need a tester that will measure the resistance of the spiral.

You must first disconnect the battery from the on-board power supply. Then set the tester to ohmmeter mode, touch the spark plug terminal with the positive contact, and touch the vehicle ground with the negative contact. The resistance indicator on a working spark plug is very small, and the tester does not always detect it. But resistance close to infinity indicates a broken spark plug (no contact).

Tester connection diagram: 1, 2 – for a single-pole spark plug, 3 – for a double-pole spark plug.

If an almost new spark plug fails, this indicates a malfunction in the fuel system or electronic control and requires professional diagnostics.

How is the glow plug checked in a diesel engine?

Which spark plugs are best for a VAZ 2107 carburetor with BSZ?

There are several ways to check the working condition of the elements. This can be done through the engine or separately from it. In order to check the performance of glow plugs outside the engine, that is, without screwing them in, you need an ohmmeter or voltmeter. These devices are used to check the voltage status. If one or the other is missing, you can check in the following way: connect the spark plug to the battery, connect the plus to the terminal, and connect the minus to the body of the element being measured.

After a few seconds, the spiral of a working spark plug will heat up, then it will begin to glow, this will indicate its functionality. If no reaction occurs, the incandescent element must be replaced. Another way to check their performance is to use a tire. To do this, install inverted candles on it, the ends of which should be directed upward. Then, using wires with a relatively large cross-section, the “ground” is closed, attaching the conductors to the body of each spark plug.

Some engine repair instructions describe a method for checking the operation of glow elements through the holes provided for the injectors. Having previously unscrewed them, observe how the pins glow, red-hot from heating. If one or more elements light up less brightly than the others, or do not light up at all, you need to check their electrical connections and then check the resistance value.

Additional "chips"

To improve the functionality of candles, manufacturers are constantly improving them: even small “pluses” can significantly improve operation.

A pressure sensor in the combustion chamber is an additional functionality that reduces NOx emissions. The sensor transmits information about the pressure in the combustion chamber to the ECU, which, in turn, adjusts the fuel supply.

One of the “weak points” is the heater rod, which breaks if installed incorrectly (at the wrong angle). Leading manufacturers produce spark plugs with a flexible axial shaft that can bend rather than break. The second solution to the same problem is a movably fixed central rod that compensates for excess pressure when tightening the spark plug.

The spark plug body is coated with zinc, which has anti-corrosion properties. This makes it easier to replace and extends its service life.

Standardization

Modern glow plugs are standardized according to ISO, which allows you to select plugs according to strictly defined technical parameters:

• Diameter and pitch of fastening thread: from M10x1.0 to M18x1.5;
• Wrench size: 12, 14, 17, 21 mm;
• Cone slope: 63, 93, 123°;
• Total length: 58-137 mm;
• Working part length: 17.35 mm;
• Working part diameter: 4-6 mm.

Glow plugs do not require special attention and frequent replacement. The only condition is a competent choice and installation, after which this issue will be closed for a long time.

To learn how to choose new glow plugs and which brands are the best on the market, read our Buyer's Guide.

How to check glow plugs on a diesel engine at home?

In winter, owners of diesel cars rely on glow plugs, which help start a cool engine. But situations often occur when even these “assistants” do NOT cope with the task assigned to them, and starting a cool engine on a frosty winter morning becomes simply impossible. Now I will talk about why this happens, how to deal with it, and also the most important thing. how to check glow plugs on a diesel engine at home, using 3 different methods.

As you understand, glow plugs. are very important for a diesel engine, especially when the temperature drops below 0 ° C. This invention makes heating the combustion chamber essential, so ignition of the fuel mixture in the cylinders becomes possible even at very low temperatures.

Modern diesel engines have more advanced heating systems, which cannot be said about old diesel engines. Once upon a time, diesel engines used glow plugs almost every time they started, despite the fact that there was no particular need for this, especially in the summer. For example, modern diesel engines start successfully even without glow plugs.

The glow plugs must be turned on at a certain temperature, and the corresponding indicator lights up on the device panel. What to do when this doesn't happen? Of course, inspect what's going on. How to check glow plugs.