How to determine the condition of spark plugs by appearance

Diagnostics of engine operation based on the condition of spark plugs

Photo No. 1 shows a spark plug removed from an engine whose performance can be considered excellent. The skirt of the central electrode is light brown in color, soot and deposits are minimal. Complete absence of oil traces. The owner of this engine can only be envied, and there is something to be said for its economical fuel consumption and the absence of the need to add oil from replacement to replacement.

Photo No. 2 shows a typical example of a spark plug from an engine with high fuel consumption. The central electrode is covered with velvety black soot. There are several reasons for this: a rich air-fuel mixture (incorrect carburetor adjustment or injector malfunction), clogged air filter.

The third photo, on the contrary, is an example of an excessively lean air-fuel mixture. The color of the electrode is from light gray to white. There is cause for concern here. Driving with a too lean mixture and under increased loads can cause significant overheating of both the spark plug itself and the combustion chamber, and overheating of the combustion chamber is a direct path to burnout of the exhaust valves. Skirt of the central electrode of the spark plug shown in the photo

№4 has a characteristic reddish tint, this color can be compared to the color of red brick. This redness is caused by the engine running on fuel containing an excessive amount of metal additives. Long-term use of such fuel will cause metal deposits to form a conductive coating on the insulation surface, through which it will be easier for current to pass than between the electrodes of the spark plug, and the spark plug will stop working.

Photo No. 5. The candle has pronounced traces of oil, especially in the threaded part. An engine with such spark plugs after a long period of parking tends to “triple” for some time after starting, and as it warms up the operation stabilizes. The reason for this is the unsatisfactory condition of the oil seals. There is increased oil consumption. In the first minutes of engine operation, at the moment of warming up, there is a characteristic white and blue exhaust.

The spark plug in photo No. 6 was removed from a non-functioning cylinder. The central electrode and its skirt are covered with a dense layer of oil mixed with drops of unburnt fuel and small particles from the destruction that occurred in this cylinder. The reason for this is the destruction of one of the valves or the breakage of the partitions between the piston rings with metal particles getting between the valve and its seat. In this case, the engine “troubles” incessantly, a significant loss of power is noticeable, fuel consumption increases by one and a half, two times. There is only one way out - repair.

Photo No. 7 is a complete destruction of the central electrode with its ceramic skirt. The cause of this destruction could be one of the following factors: prolonged operation of the engine with detonation, the use of low octane fuel, very early ignition, and simply a defective spark plug. The engine operating symptoms are the same as in the previous case. The only thing you can hope for is that the particles of the central electrode managed to slip into the exhaust system without getting stuck under the exhaust valve, otherwise repairing the cylinder head cannot be avoided. But it depends on the person, whether he is sinful or not (just kidding). If we talk about this particular candle, then God had mercy on its owner.

Photo No. 8 is the last one in this review. The spark plug electrode is overgrown with ash deposits; the color does not play a decisive role, it only indicates the operation of the fuel system. The reason for this build-up is the combustion of oil due to wear out or jamming of the oil scraper piston rings. The engine has increased oil consumption, when over-gasping, there is strong blue smoke from the exhaust pipe, and the smell of the exhaust is similar to that of a motorcycle. If you want to have fewer problems with the operation of your engine, do not think about spark plugs only when the engine refuses to work. The manufacturer guarantees trouble-free operation of the spark plug on a working engine for 30 thousand kilometers. But you, in turn, do not forget to check the condition of the spark plugs with every oil change or on average every 10 thousand kilometers. First of all, this is adjusting the gap to the required value and removing carbon deposits. It is better to remove carbon deposits with a metal brush; sandblasting destroys the ceramics of the central electrode, and you risk getting a copy of photo No. 7. I would also recommend swapping spark plugs, this is due to different temperature conditions of the cylinders.

1. Normal spark plug Brown or grayish-yellowish color and slight wear on the electrodes. Exact matching of the spark plug thermal value for the engine and operating conditions.

HELPFUL ADVICE! When replacing spark plugs with new ones, install spark plugs with the same characteristics recommended by the manufacturer.

2. Soot deposits

Dry soot deposits indicate a rich air/fuel mixture or late ignition. Causes misfire, difficult engine starting and unstable engine operation. Check if the air filter is clogged and if the coolant and intake air temperature sensors are working properly.

HELPFUL ADVICE! Use a hotter candle.

3. Oil deposits Oily electrodes and spark plug insulator. The reason is oil entering the combustion chamber. Oil enters the combustion chamber through valve guides or rings. Causes difficult starting, cylinder misfires and “twitching” of a melting engine. The cylinder head and piston engine need to be repaired. Replace spark plugs.

4. Metal-containing deposits Deposits on the insulator skirt of iron oxides of brick-red color from anti-knock iron-containing additives (ferrocenes) to gasoline. They are deposited in an even, dense layer. When the engine operates under heavy load under the influence of high temperature and pressure in the combustion chamber, the oxides are reduced into conductive tracks of pure iron, which close the central electrode to ground. This causes misfires and, as a result, a drop in engine power and increased fuel consumption. In addition, the catalytic converter of the exhaust gases may be damaged, overheating greatly when unburned gasoline enters the engine cylinders. The plaque is practically not removed mechanically and does not fade during prolonged movement at high speed. If this deposit appears on new spark plugs after a short mileage, change the refueling location.

HELPFUL ADVICE! If it is not possible to immediately replace the spark plugs with new ones, try removing this deposit by immersing the spark plugs for ten minutes in orthophosphoric acid or a rust converter (contains phosphoric acid). After this, clean the deposits with a non-metallic brush (or an old toothbrush) and rinse the spark plugs, first with water and then with gasoline.

5. Early ignition Melted electrodes. The insulator is white, but may be contaminated due to misfires and combustion chamber deposits. May cause engine damage. It is necessary to check the suitability of the spark plug type, the cleanliness of the injector nozzles and fuel filter, and the operation of the cooling and lubrication systems.

6. Detonation The insulator may be cracked or chipped. This may damage the piston. Make sure that the octane number of gasoline matches the required one.

7. Mechanical damage Damage can be caused by foreign objects getting into the combustion chamber, and if a spark plug is too long, its electrodes may catch on the piston. This causes spark plug destruction, cylinder shutdown and can damage the piston. Remove the foreign object from the cylinder and/or replace the spark plug.

pensia › Blog › Diagnostics of engine operation based on the condition of the spark plugs.

Spark plugs, these simple-looking compounds of metal and ceramic, are the most important element in the operation of an engine. Even by the appearance of the spark plug you can tell a lot, both about the operation of the engine as a whole and about its individual components. Inspection of the spark plug should be carried out after prolonged operation of the engine; the ideal option would be to inspect the spark plug after a long trip on a country highway.

Photo No. 1 shows a spark plug removed from an engine whose performance can be considered excellent. The skirt of the central electrode is light brown in color, soot and deposits are minimal. Complete absence of oil traces. The owner of this engine can only be envied, and there is something to be said for its economical fuel consumption and the absence of the need to add oil from replacement to replacement.

Photo No. 2 shows a typical example of a spark plug from an engine with high fuel consumption. The central electrode is covered with velvety black soot. There are several reasons for this: a rich air-fuel mixture (incorrect carburetor adjustment or injector malfunction), clogged air filter.

The third photo, on the contrary, is an example of an excessively lean air-fuel mixture. The color of the electrode is from light gray to white. There is cause for concern here. Driving with a too lean mixture and under increased loads can cause significant overheating of both the spark plug itself and the combustion chamber, and overheating of the combustion chamber is a direct path to burnout of the exhaust valves. Skirt of the central electrode of the spark plug shown in the photo

No. 4 has a characteristic reddish tint, this color can be compared to the color of red brick. This redness is caused by the engine running on fuel containing an excessive amount of metal additives. Long-term use of such fuel will cause metal deposits to form a conductive coating on the insulation surface, through which it will be easier for current to pass than between the electrodes of the spark plug, and the spark plug will stop working.

Photo No. 5. The candle has pronounced traces of oil, especially in the threaded part. An engine with such spark plugs after a long period of parking tends to “triple” for some time after starting, and as it warms up the operation stabilizes. The reason for this is the unsatisfactory condition of the oil seals. There is increased oil consumption. In the first minutes of engine operation, at the moment of warming up, there is a characteristic white and blue exhaust.

The spark plug in photo No. 6 was removed from a non-functioning cylinder. The central electrode and its skirt are covered with a dense layer of oil mixed with drops of unburnt fuel and small particles from the destruction that occurred in this cylinder. The reason for this is the destruction of one of the valves or the breakage of the partitions between the piston rings with metal particles getting between the valve and its seat. In this case, the engine “troubles” incessantly, a significant loss of power is noticeable, fuel consumption increases by one and a half, two times. There is only one way out - repair.

Photo No. 7 is a complete destruction of the central electrode with its ceramic skirt. The cause of this destruction could be one of the following factors: prolonged operation of the engine with detonation, the use of low octane fuel, very early ignition, and simply a defective spark plug. The engine operating symptoms are the same as in the previous case. The only thing you can hope for is that the particles of the central electrode managed to slip into the exhaust system without getting stuck under the exhaust valve, otherwise repairing the cylinder head cannot be avoided. But it depends on the person, whether he is sinful or not (just kidding). If we talk about this particular candle, then God had mercy on its owner.

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Photo No. 8 is the last one in this review. The spark plug electrode is overgrown with ash deposits; the color does not play a decisive role, it only indicates the operation of the fuel system. The reason for this build-up is the combustion of oil due to wear out or jamming of the oil scraper piston rings. The engine has increased oil consumption, when over-gasping, there is strong blue smoke from the exhaust pipe, and the smell of the exhaust is similar to that of a motorcycle. If you want to have fewer problems with the operation of your engine, do not think about spark plugs only when the engine refuses to work. The manufacturer guarantees trouble-free operation of the spark plug on a working engine for 30 thousand kilometers. But you, in turn, do not forget to check the condition of the spark plugs with every oil change or on average every 10 thousand kilometers. First of all, this is adjusting the gap to the required value and removing carbon deposits. It is better to remove carbon deposits with a metal brush; sandblasting destroys the ceramics of the central electrode, and you risk getting a copy of photo No. 7. I would also recommend swapping spark plugs, this is due to different temperature conditions of the cylinders.

Soot coloring

During long-term operation, the SZ cannot be perfectly clean, and many people are interested in what the carbon deposits should be like if the car is in good working order, and why this is not always the case. In a situation where the car engine is absolutely in good working order, when you turn out the spark plug, you can see a brownish coating - from light to dark shades of brown. This indicates that the electrode burned out evenly during the operation of the car. If all auto components operate correctly, the service life of ignition elements usually reaches 30,000 km. Modern models of two and three-electrode spark plugs may not need to be changed twice as long. If, upon inspection, the car owner discovers that the spark plugs have carbon deposits of completely different colors, this means that there are obvious irregularities in the operation of the engine. Let's look at the possible types of soot.

White soot

White deposits on spark plugs usually come in several shades, which indicate slightly different problems:

Grayish tint. This is clear evidence of the use of low-quality fuel. In this case, it is enough to unscrew the SZ and clean it, and they will be ready for further use. An important condition for eliminating the problem will be changing bad gasoline.
Shiny deposits combined with erosions on the contact electrodes. In this case, you can be firmly sure that the spark plugs are overheating. This situation is often caused by low-quality fuel, incorrectly selected fuel protection, or problems with the cooling system. After eliminating the causes of soot formation, the spark plugs may have to be replaced. In this case, you will need to pay more attention to their thermal characteristics.
White coating. It should not be confused with carbon deposits. Plaque occurs due to antifreeze entering the engine cylinder. Quite often this process is accompanied by the appearance of white smoke from the exhaust pipe. If you smell the candles, you can feel a pronounced sweetish smell. To eliminate this problem, you will need to eliminate the ingress of antifreeze and only then replace the ignition elements.

The working part is covered with black soot

Black spark plugs are a symptom indicating that the fuel mixture is too rich (the proportion of gasoline is increased above normal). Therefore, the fuel does not burn completely and forms a layer of soot on the chamber walls and spark plug electrodes.

An additional sign of this problem is black or dark gray smoke from the exhaust. When over-gassing, small flakes of soot may fly out of the pipe.

There are quite a few reasons for the enrichment of the air-fuel mixture, the most common ones look like this:

One of the key sensors has become unusable - air flow, temperature, throttle position or oxygen content in the exhaust (lambda probe). The controller activates the emergency program and prepares the mixture according to other indications.
Carburetor malfunctions (clogged air jets, worn throttle valves, etc.).
Failure of the pressure regulator in the fuel line.
Wear of nozzles - nozzles “overflow” and leak when the power unit is not working.
Problems with sparking - the power of the electrical pulse is not enough to ignite the combustible mixture normally.

Important! If during the diagnostic process you find black spark plugs, the fault should be found immediately. Increased gasoline consumption is only part of the consequences of excessive enrichment.

There are others, not so harmless:

some of the unburned fuel penetrates the crankcase and dilutes the oil, accelerating the wear of engine parts;
the other part gets into the exhaust manifold, which is why shots are periodically heard in it;
soot clogs the expensive catalytic converter - it has to be cleaned or replaced with a new one;
The service life of the spark plugs is sharply reduced.

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When running on a rich fuel mixture, the engine “chokes”, unstable idling and skipped cycles are observed. When a certain amount of soot heated to a high temperature accumulates in the chambers, a “pseudo-diesel” effect occurs - after turning off the ignition, the engine does not want to stall and makes 2-10 crankshaft revolutions. The reason is hot soot, igniting the combustible mixture without a spark.

Oily texture

In response to the presence of oily deposits, diagnostics of spark plugs based on the appearance of the insulator will issue an expert conclusion - oil is entering the combustion chamber. Electrodes are wet due to lubricant - major repairs cannot be avoided. The situation shown in the photo can happen for three reasons:

Valve seals are worn out.
The life of the piston rings is coming to an end.
The valve guides are broken.

Compression measurements will help separate the culprits. If it is normal, then the problem is related to the tightness of the valves. The following aspect also has the right to life: the thread in the oil is the reason in the cylinder head (with bushings/valve caps). It is possible that lubricant may leak from under the valve cover through the spark plug well.

In parallel with the deposition of oil on the electrodes of the spark plugs, the muffler emits white-blue gases. Another possible symptom is the power plant tripping at the beginning of warm-up.

For reference. A particular variation of the signs of an oil-air emulsion entering the combustion chamber is ash deposits. This deposit occurs due to the combustion of the additive package included in the oil by the manufacturer. If this fact is discovered, the rings should be decarbonized.

Loose black dry soot

Velvety black color primarily indicates increased fuel consumption. It may be caused by improper carburetor adjustment. On an injection engine, the reason may lie in the malfunctioning of the ECU, associated with incorrect readings of some sensors. A clogged air filter will also cause the mixture to become over-rich.

A matte, loose black coating also appears during prolonged operation of the internal combustion engine at idle or short trips within the city. It is noteworthy that this structure is formed only on the electrodes. The thread remains clean. More detailed reasons are considered separately for the methods of preparing fuel assemblies and will be given below.

Hard black deposits

Such deposits indicate one thing - the spark plug does not correspond to the engine in terms of temperature characteristics. In other words, the igniter has too high a heat value. In fact, this indicates that the product is “cold”, that is, its self-cleaning temperature in the combustion chamber is not reached.

Origin of red plaque

This phenomenon is less common than the effects described above. Why are there red electrodes on some spark plugs?

the tank is filled with low quality gasoline with additives that increase the octane number;
a car enthusiast or a fuel supplier adds additives to gasoline, which contain a large amount of metals;
the owner of the car installed spark plugs in the cylinders that did not match the heat rating.

The reasons for the reddish tint of spark plugs do not pose a direct threat to the power unit, but are harmful in the long term.
Driving on low-quality gasoline with unknown additives a priori accelerates the wear of parts and components. Plus an increase in consumption arising from worsening combustion conditions of the mixture in the cylinders. Operating a car with spark plugs that are “cooler” or “hotter” in terms of heat rating reduces engine power and significantly shortens the life of the elements. A characteristic sign of incorrectly selected spark plugs is a drop in crankshaft speed at idle and missed ignition cycles.

Erosion

Quite often, the addition of metal-containing additives to fuel results in erosion at the ends of the electrodes. This is a 100% sign that the spark plugs are no longer suitable for use. Along with replacing the spark plugs, as in the previous case, you will have to change the gas station.

Ash deposit

Sometimes on the ignition elements you can see a coating similar to ash, with completely different shades. In this case, you may suspect a breakdown in the injector or carburetor ignition system. The spark plugs need to be cleaned, if possible, or new ones installed. After a run of 150 km. you need to check the condition of the spark plugs again. If signs of gasoline appear, a trip to a car repair shop to check the carburetor becomes inevitable.

Yellow soot

Sometimes you can see yellowish or even green rims on candles. This is also the result of using low quality fuel, which contains lead. Irreversible consequences for the car in such a situation are not expected in the near future, but it is worth considering whether you need to overpay for such quality gasoline or whether it is worth changing the gas station. Replacing spark plugs in this case is highly desirable.

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Los4inin › Blog › Diagnostics of internal combustion engines based on the condition of spark plugs

Spark plugs, these simple-looking metal and ceramic connections, are a critical element in engine performance. Even by the appearance of the spark plug, you can tell a lot about both the operation of the engine as a whole and its individual components.

Inspection of the spark plug should be carried out after prolonged operation of the engine; the ideal option would be to inspect the spark plug after a long trip on a country highway. The mistake of some car enthusiasts, for example, is that after a cold start of the engine at sub-zero temperatures and its unstable operation, the first thing they do is unscrew the spark plugs and when they see black carbon deposits, they draw hasty conclusions. But this carbon deposit could form during engine operation in cold start mode, when the mixture is forcibly enriched, and unstable operation could be a consequence of, say, the poor condition of high-voltage wires.

Running an engine on leaded gasoline results in the formation of conductive, yellowish-brown deposits, which also reduce the likelihood of a spark forming at the spark plug. At room temperature, the presence of conductive deposits is not detected by instruments (ohmmeter).

Photo No. 8 The spark plug electrode is overgrown with ash deposits, the color does not play a decisive role, it only indicates the operation of the fuel system. The reason for this build-up is oil combustion due to depletion or obstruction of the oil scraper piston rings and the unsatisfactory condition of the oil seals. The engine has increased oil consumption, when over-gasping, there is strong blue smoke from the exhaust pipe, and the exhaust smell is similar to that of a motorcycle.

Photo No. 9 Destruction of a ceramic insulator. Causes of occurrence: a sharp change in temperature, for example when a spark plug removed from a hot engine is cooled in cold water. In some cases, destruction may be caused by a defect in the candle itself (defective or counterfeit), or by mechanical damage, for example as a result of a fall.

Signs of electrode erosion: the engine performs poorly, runs unstably even after warming up, misfires, and does not develop the required power.

Photo No. 11 Spraying a candle with gasoline. Often occurs due to a malfunction of the ignition system or carburetor / injector (flow). In winter, this can occur due to the fact that gasoline entering the combustion chamber does not have time to evaporate and settles on the spark plugs and cylinder walls. The solution is to unscrew the spark plugs and wash them with alcohol and let them dry or blow them with air. If you want to have fewer problems with the operation of your engine, do not think about spark plugs only when the engine refuses to work. The manufacturer guarantees trouble-free operation of the spark plug on a working engine for 30 thousand kilometers. But you, in turn, do not forget to check the condition of the spark plugs with every oil change or on average every 10 thousand kilometers. First of all, this is adjusting the gap to the required value and removing carbon deposits. It is better to remove carbon deposits with a metal brush; sandblasting destroys the ceramics of the central electrode, and you risk getting a copy of photo No. 7.

It is recommended to periodically change spark plugs, this is due to different temperature conditions of the cylinders.

Other deposits and deposits

White plaque is not the only possible deviation from the normal state of the electrodes. To correctly assess risks, you need to know the meanings of other shades of deposits.

Black

The following problems can cause the appearance of black soot:

Over-enriched mixture, fuel sensor problems (dry residue remains on the electrode).
Unsuitable “cold” candles.
Air filter clogged.
Oil combustion (shiny, sooty electrode and thread).
Loose nozzle fit or broken check valve.

With late ignition and a small advance angle, the spark plugs turn black even with the correct choice of heat rating and gasoline.

Red and brown

Scarlet, brown and red soot is a consequence of the use of low-quality fuel with ferrocene, manganese or lead additives. A thick red layer can make it difficult for a spark to pass through and disrupt the operation of the engine, so when it appears, it is recommended to change the brand of oil or gas station.

Zolny

Ash soot can be both light and dark. When it appears, increased oil consumption, decreased power, and darkening of the exhaust gases are observed.

The cause of the problem is worn or stuck piston rings.

Erosion

If the spark plug is defective, early ignition, or prolonged operation on low-octane or low-quality fuel, erosion (destruction) of the central electrode may occur. At the same time, the power of the internal combustion engine decreases, and when driving, jerking, instability at idle and “triple” are observed. The part requires immediate replacement.

Gasoline on spark plugs

Filling of spark plugs occurs when there is a malfunction of the fuel system, injector or carburetor, less often when starting in cold weather. To solve the problem, you need a complete diagnosis of the car and repair of damaged parts of the internal combustion engine.

Oil and fuel deposits

A shiny yellow or dark coating indicates grease penetration and wear of the valve seals. A characteristic accompanying symptom is blue smoke and high engine oil consumption.

Fuel carbon deposits occur when valves become depressurized or the piston system wears out. At the same time, against the backdrop of a drop in power and unstable operation of the internal combustion engine, gasoline consumption increases.

In more rare cases, a green coating is observed on the electrodes. Its cause may be the presence of additives in gasoline or the ingress of antifreeze into the combustion chamber.

How to check spark plugs

Signs of contamination or failure of spark plugs appear in the form of interruptions in engine operation; an engine with dirty or problematic spark plugs will suffer. This happens because all the candles usually do not fail at once. Interruptions begin in only one or two cylinders. The first step is to identify the spark plug that has failed. There are several ways to check spark plugs:

using a device or tester to check spark plugs;
independent checking of spark plugs;

To check the spark plugs, you need to remove them, although there are also ways to diagnose spark plugs on a car. Before starting the procedure that involves removal, you should turn off the ignition and prepare a special spark plug or socket wrench. You will need a tool to unscrew the spark plugs. Then you need to inspect the high-voltage armored ignition wires. These wires usually have special markings that contain information about the cylinder number. If there is no such marking, you will need to mark the high-voltage spark plug wires yourself in an accessible way.

The next step is to remove the tips (caps) from the spark plugs. Please note that you should not pull on the high-voltage wire while performing this procedure, as this may damage the armor wire. To remove it, you need to hold onto the tip itself. After removing the spark plug caps, you can unscrew the spark plugs using a wrench. V-twin engines will require a long drive wrench, similar to a torque wrench. An extended collar will also work.

During removal, you should remember which cylinder each unscrewed spark plug corresponds to, since further inspection will allow you to determine possible malfunctions not only of the spark plugs, but also of the engine based on the condition of the spark plugs. Checking the spark plugs should begin with a visual inspection and checking the condition of the insulator, as well as the electrodes. Cracks or melting, as well as other noticeable defects, are not allowed. Next, the candles are installed on a special stand or checked with a device. As mentioned above, motorists also check the spark plug directly on the car or use a multimeter. We will talk about various verification methods below.

Checking spark plugs for spark

To check the spark plug for a spark, you need to disconnect the high-voltage wires that connect the spark plugs and the distributor breaker one by one. This must be done with the car running. After removing the wire, listen to the engine. If the operation of the motor has not changed, then this means that it was possible to find the failed element. If, after disconnection, the motor begins to operate even less stably, the test must be continued.

The next way to check the spark on the spark plugs is to remove the high-voltage wire, after which the spark plug is unscrewed. Then the spark plug is inserted back into the armored wire cap and brought to the cylinder block. As a result, a clearly visible spark should appear on the spark plug, which will be accompanied by a characteristic crackling sound. This method allows you to diagnose the operation of the ignition system, wire and spark plug.

Let us add that it is more correct to check the high-voltage ignition wires with a multimeter. This device is capable of measuring the resistance of the wire, after which it should be compared with the nominal one. A drop in voltage will indicate the need to replace the armor wire.

Another way is to check the spark plugs with a “gun”. Such a “gun” for checking candles is a testing stand that is available from candle sellers. This equipment allows you to test spark plugs under pressure, that is, their operating conditions in the engine are partially simulated.

Checking the spark plug on the stand is carried out as follows:

the spark plug is inserted into the groove;
then a special cap is put on it;
then all that remains is to pull the trigger of the “gun” to check the spark plugs;

The appearance of a spark on the electrodes and the lighting of the warning light most likely indicates the serviceability of the spark plug, although this test method cannot guarantee full functionality. The fact is that the pressure on the stand and in the engine is different. For this reason, a spark plug previously tested on a bench with a good spark may still not work after being installed on the engine. If the spark plug initially does not work on the stand, then this element should be replaced due to an obvious malfunction.

Fuel pollution

The insulator and electrodes of the spark plug are covered with wet black deposits. The candle smells like fuel.

This indicates that at some engine operating modes the power system is preparing a fuel mixture that is too rich. It does not burn completely and produces a large amount of soot. In addition, the cause of this phenomenon may be unstable operation of the ignition system, leading to spark failures, as well as the use of an excessively “cold” spark plug.

The spark plug can be restored. To do this, you need to wash it in gasoline, clean it with a copper brush and dry it. But this will solve the problem only for a while: if you do not find out and eliminate the cause of the malfunction, the spark plug will soon return to its previous appearance.

How to clean the spark plugs yourself and set the gap between the electrodes

After removal and external inspection, the spark plug must be carefully cleaned of dirt, soot, carbon deposits and deposits. This can be done mechanically, using a brush that has medium-hard bristles. It is also possible to use an abrasive.

The mechanical method allows you to efficiently remove carbon deposits, but the performance characteristics of the spark plug usually become worse. This type of cleaning usually results in scratches, which then cause the spark plug to overheat. For this reason, it is necessary to clean spark plugs from deposits as delicately as possible.

You can also clean spark plugs chemically:

the candle is degreased and washed in gasoline;
then the candles are dried for 30 to 60 minutes;
then the candles are placed in a solution of ammonium acetate for 30-40 minutes;

The advantage is a reduced risk of mechanical damage. The completion of cleaning is to check the gap between the electrodes of the spark plugs. The gap between the spark plug electrodes is assessed after mechanical cleaning.

The gap normally should not differ from the 0.7 mm mark. The specified gap must be checked using a special feeler gauge. If the gap is different, it needs to be adjusted. Adjusting the spark plug gap is performed with a special tool, and the process itself involves bending or bending the side electrode from the central electrode. Let us add that bending the central electrode is prohibited, and bending the side electrode should be done with extreme caution.

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Carbon formation

Black soot accumulates on the heat cone of the insulator and the electrodes of the spark plug, with a texture reminiscent of suede.

Most often, this is a consequence of an error in determining the thermal characteristics of the candle. It is too “cold” for this engine. The spark plug elements do not reach the self-cleaning temperature. Perhaps this is a consequence of the so-called “city driving” with low speeds, frequent stops and starts.

If the spark plug has no other defects, its performance can be restored by cleaning or heating. However, if you do not intend to change your driving style, it is more advisable to replace the spark plug with a “hotter” one (i.e. with a lower glow number).

Engine condition by spark plug color

The serviceability of the engine and spark plugs is determined by the color of the deposit that is present on the electrodes. We will not describe all possible options for diagnosing the engine condition by the color of the spark plugs, since this is the topic of a large separate article. We only note that a working spark plug normally has a light grayish-brown coating.

The appearance of black dry soot on the electrode indicates the need to check the fuel system of the internal combustion engine. Such deposits form when the engine operates on a highly enriched mixture. The spark plug can then be cleaned and screwed back into the engine for further use.

Installing cleaned or new spark plugs into the engine at the initial stage is done by hand. In other words, the candles need to be “baited” by hand, that is, carefully screwed into the candle wells without using a key. If the spark plug is easily screwed into the thread, then the element can be tightened with a wrench until the conical part comes into contact with the cylinder head.

Remember, when tightening the spark plugs, it is highly advisable to strictly adhere to the tightening torque specified in the technical documentation for a specific engine type! Retightening the spark plug may lead to the need for subsequent repair of the cylinder head and other consequences. As for loosely twisted spark plugs, an under-tightened spark plug can cause engine malfunctions.

Tips and tricks

If new spark plugs quickly change color after installation, become overgrown with carbon deposits and again cause engine malfunctions, then the following options are possible:

spark plugs are incorrectly selected;
a counterfeit or defective product was purchased;
the engine is operated on low quality gasoline or oil;
there are engine malfunctions that quickly disable new spark plugs;

Finally, let us add once again that spark plugs, as well as high-voltage spark plug wires, are “consumables”, that is, they need to be completely changed at certain intervals. If the engine previously had a malfunction that simultaneously damaged the spark plugs, then after eliminating such a breakdown of the engine, it is recommended to also replace the set of spark plugs.

How to read spark plugs? How to diagnose engine problems using spark plugs?

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Yes, spark plugs are the most valuable among the simplest methods for diagnosing various kinds of engine problems. You can actually "read" your spark plugs and get valuable clues about how your car's engine is performing, what it's missing most, and where trouble is coming from.

Of course, to read a spark plug and evaluate engine problems, you must first remove it. Use a spark plug wrench for this.

You can read more about how to remove a spark plug in the article on replacing spark plugs. First, let's take a look at what main parts a spark plug consists of:

As you can see, everything is extremely simple and obvious. Now let's take a look at what spark plug conditions mean, how to correctly diagnose engine malfunctions and problems based on such conditions, as well as options for solving problems.

Select from the images below what your spark plug looks like:

Normal candle

A coating of coffee, brown or gray-brown color on the white skirt (if the car runs on gas, the color will most likely be brown), and small traces of erosion on the electrodes.

The engine is running normally.

Worn spark plug

This is a normal process for the spark plug to wear out and require replacement. Remember that spark plugs need to be changed regularly because as they wear, the gap between the spark plug electrodes increases, which requires more voltage to produce a spark.

The normal growth rate of the gap for most spark plugs is considered to be as follows: for four-stroke engines: 0.01

Ash deposits

The central and side electrodes are covered with an ashy coating. As a result of this “masking” of the electrodes, your engine may experience misfires. In advanced cases, this accumulation of combustion deposits may eventually (but usually does not) fill the entire gap between the two electrodes.

Causes:

Poor fuel quality (presence of harmful additives).
Oil enters the combustion chamber due to leaking piston rings or other reasons.

What to do:

Replace spark plugs.
Change your usual gas station.
Check engine compression to determine the need for overhaul.

Dry black carbon

Black, dry, even possibly fluffy soot deposits on the tip of the insulator and electrodes. Accompanied by noticeably increased fuel consumption.

Causes:

Excessively rich air-fuel mixture (AFM).
Dirty air filter (and, as a result, too rich BTC).
Driving at low speeds too often or idling for long periods of time.
Incorrect carburetor or injector adjustment (for example, faulty oxygen sensor).
If only one or several spark plugs (but not all) are covered with such soot, then the cause may be in the ignition system (ignition wires, distributor).

What to do:

Check and replace the air filter.
Diagnose injector malfunctions or adjust the carburetor.
Replace the wires or the ignition distributor cap (if the problem is only with some spark plugs).

Candle in oil

Wet, black oil deposits on the tip of the skirt and electrodes. The engine does not start well and may misfire.

When starting the engine when cold, it may “sputter” and blue or white-blue smoke comes out of the exhaust pipe. Accompanied by increased oil consumption.

Causes:

This is often the cause of severely worn piston rings or cylinder walls.
Oil can also be drawn into the chamber due to excessive clearance in the valve stem guides, or severely worn valve seals.
Worn oil seals.
The spark plug is too “cold” (the temperature of the spark plug is inappropriate for the engine).

What to do:

Check engine compression for possible major repairs.
Adjust valves or replace valve seals.
Replace the spark plug with a hotter one.

Burnt candle

Bubbles on the skirt of the central tip, melted electrodes and other traces of exposure to high temperatures. A burnt spark plug means that the spark between the electrodes is flowing at a higher temperature, and the temperature will only rise as the plug wears further, so it needs to be replaced as quickly as possible.

Accompanied by loss of engine torque and increased gasoline consumption. The engine may not stall immediately after the spark stops (turning off the ignition with the key).

Causes:

Engine overheating.
Incorrectly adjusted ignition (ignition advance).
Too poor fuel assembly.
Incorrect spark plug temperature for the engine (too cold)
Driving with a heavy load.

What to do:

Replace burnt spark plugs (with suitable temperature setting).
Adjust the ignition.

Contamination (glazing) of the skirt

This symptom can cause misfire at high engine speeds. Glossy deposits are usually yellow in color.

Causes:

This symptom indicates the use of gasoline with a high lead content.

What to do:

The usual gas station should be replaced.

Reddish skirt

The spark plug skirt becomes covered with a reddish tint - it is conductive.

Causes:

Increased content of heavy metals in gasoline and their deposition on the skirt (and other parts) of the spark plug.

What to do:

The usual gas station should be replaced.

Mechanical damage to the entire spark plug

The side electrode has broken off, or even the entire spark plug has mechanical damage. In this case, the cylinder most likely will not work.

Causes:

Mechanical damage is caused by a foreign object in the combustion chamber.

What to do:

Check the combustion chamber for foreign objects.

Mechanical damage to the skirt

The skirt of the central electrode is broken or has slight mechanical damage.

Causes:

Detonation, as a result of which overpressure was formed, which destroyed the skirt as the weakest part of the working surface of the spark plug. And the reasons for such detonation:

Incorrectly adjusted ignition timing.
Faulty exhaust gas recirculation valve.
Insufficient octane number of gasoline.
Sudden cooling of the candle.
The spark plug itself is defective.

What to do:

Adjust the ignition timing.
Check the exhaust gas recirculation valve.
Check that the octane number of the gasoline used matches the characteristics of the car.

The candle melted

Both or one of the electrodes appears scorched or melted. In this case, the machine may also experience a loss of power.

Causes:

Incorrectly adjusted ignition timing.
Lean air-fuel mixture.
The spark plug is too “cold” according to its characteristics.

What to do:

Choose a suitable candle if the reason is a mismatch in temperature conditions.
Check the ignition timing.

Side electrode erosion

The side electrode is corroded, or appears melted, becoming much shorter, not reaching the center electrode along its length.

Causes:

Gasoline with high lead content. Lead most often affects only the side electrode, since it is made of a nickel alloy and reacts chemically with lead, becoming brittle and weak.

What to do:

Change your usual gas station.

Metal "zipper" on the outer insulator

On the outer insulator (which is located outside the engine when the spark plug is screwed into the engine) there is a twisting metal strip.

Causes:

This is the result of the spark gap between the spark plug electrodes having widened greatly due to wear on the electrodes, and the spark plug requires a much higher voltage. Such lightning on an insulator occurs when the required voltage between the pins of the electrodes is higher than the insulator can support, as a result of which a spark appears not between the electrodes, but between the spark plug body and the upper contact (where the spark plug wire plug is inserted). Of course, this condition also occurs simultaneously due to worn-out insulators of the plug itself, which cannot hold the voltage.

Since higher voltage is required for turbocharged engines, these types of damage are more likely to occur. It is important to recognize that the plug is a consumable item that must be replaced periodically.

What to do:

Replace the spark plug wires and the spark plugs themselves.

Metallic plaque

Sign of low quality gasoline

. Deposits on the insulator skirt of brick-red iron oxides from anti-knock iron-containing additives (ferrocenes) to gasoline are deposited in an even, dense layer. When the engine operates under heavy load under the influence of high temperature and pressure in the combustion chamber, the oxides are reduced into conductive tracks of pure iron, which close the central electrode to ground. This causes misfires and, as a result, a drop in engine power and increased fuel consumption.

In addition, the catalytic converter may be damaged.

exhaust gases, which overheats greatly when unburned gasoline enters the engine cylinders. The plaque is practically not removed mechanically and does not fade during prolonged movement at high speed. If this deposit appears on new spark plugs after a short mileage, change the refueling location.

Advice: If it is not possible to immediately replace the spark plugs with new ones, try to remove this deposit by immersing the spark plugs with insulator skirts for ten minutes in a rust converter (contains phosphoric acid). After this, clean the plaque with a non-metallic brush (or an old toothbrush) and rinse the spark plugs first with water and then with gasoline.