What does carbon deposits on spark plugs and its color indicate?

Spark plugs perform the main function in an engine - they form a spark to ignite the mixture of fuel and air in the combustion chamber. The efficiency and quality of operation of this element of the ignition system determines the stability of the internal combustion engine, the ease of its starting, power, throttle response, fuel consumption, exhaust gas toxicity, etc. It should be borne in mind that spark plugs are a so-called “consumable”, that is, they must be changed periodically.

Experienced drivers are also well aware that the condition of the spark plugs during a check can determine not only the need to replace them, but also identify other malfunctions related to the operation of the engine and its systems.

We also recommend reading the article on how to check spark plugs for a spark on the injector. From this article you will learn about ways to independently check the spark plugs of an injection engine, as well as how to carry out such a check yourself.

Diagnosing spark plugs by the color of soot that accumulates on the electrodes and other parts makes it possible to determine the causes of such soot formation and the subsequent failure of the spark plugs themselves. In this article we will talk about what types of carbon deposits on spark plugs indicate various malfunctions and breakdowns of the internal combustion engine, why carbon deposits form on spark plugs, the reasons for the appearance of such deposits, and also how to clean spark plugs from carbon deposits at home.

Causes

Candles are subject to severe chemical and thermal effects, so their operating environment is perceived as harsh. When fuel combustion occurs on the surface of the electrodes, a grayish, dense coating appears - this condition is considered stable. If the deposit changes color, becomes red, black or greenish, this is a signal to check the operation of the system. Thanks to the shade of the plaque, you can identify the exact cause without disassembling the car. The most common symptoms are poor sparking, breakdown of engine components, low-quality fuel, and incorrect temperature conditions in the aircraft chamber.

Ash and erosion

Ash deposits are also a consequence of lubricant ingress. But the amount of lubricant that has penetrated into the cylinders is not yet very large, so it burns, releasing a large amount of wear products that settle on the electrodes in the form of ash.

Erosion on spark plug electrodes (clearly visible defects and traces of melting) occurs in two cases:

1. The first is the exhaustion of the life of the spark plugs, which causes interruptions in their operation and deterioration in spark formation. If you continue to operate the car on such spark plugs, then due to interruptions the combustion process changes, which is the cause of melting.
2. The second case is the presence of tetraethyl lead in gasoline. This additive affects the combustion process and, as a result, the spark plugs. In this case, it is enough to replace the fuel and spark plugs.

Finally, it should be noted that diagnosis by spark plug soot is only possible if these elements are in good condition. If the spark plug does not correspond to the heat rating, it has exhausted its service life or there are internal damages, then its operation will be disrupted, which is why the combustion process of the mixture will change.

Therefore, they should be replaced in a timely manner, without waiting for them to completely exhaust their service life, and furthermore, further operation of the car on worn-out spark plugs should not be allowed.

Another nuance is that interruptions in the operation of spark plugs can occur not only due to the spark plugs themselves, but also due to faulty high-voltage wires. If they have a breakdown, then the spark plug simply does not receive an electrical impulse with the parameters required for normal operation of the spark plug.

Therefore, accurate information about the operation of the power plant from the spark plugs can only be obtained if all elements that ensure sparking in the cylinders - coils, high-voltage wires, tips, spark plugs - are in full service.

Let’s imagine for a moment an internal combustion engine that is close to ideal:

• clean, free of impurities fuel (for example, hydrogen) burns in its cylinders;
• the mixture of fuel with air (more precisely, with oxygen in the air) is supplied in strict accordance with the current operating mode - that is, it corresponds both in quality and quantity;
• there are no misfires caused by electronic problems or failure of valve timing;
• There is also no engine oil in the combustion chamber;
• There are also no violations of the thermal operating conditions of the engine.

Perhaps, compliance with these conditions alone would be enough to prevent car spark plugs from becoming “overgrown” with carbon deposits. But reality dictates its own conditions, which are far from ideal, and the color of carbon deposits on spark plugs can “tell” a lot to an experienced mechanic about the condition of the engine, about the fuel, about the oil, and, the most astute, about the owner of the car.

Is it possible to find out about a malfunction by flying?

If you need to find out the localization of a problem with the ignition cycle of the working fluid, it is the spark plugs that allow you to do this most accurately. It is worth remembering that it is impossible to characterize the position of the engine by spark plugs after a run of more than 20 thousand kilometers. Diagnostic methods are effective only on new parts, “fresh” and recently installed. A prerequisite is a running-in period of at least 250 kilometers. The algorithm for checking the engine condition using spark plugs looks like this:

• new spark plugs are being installed;
• running up to 200 (or more) kilometers;
• dismantle the elements and evaluate the shade of soot.

Important: The check must be performed exclusively on a warm engine.

Light electrodes

White or light gray spark plugs in all cylinders are a sign of a lean air-fuel mixture supplied by the injector or carburetor. Moreover, the skirt, area near the electrodes and the threaded part are absolutely dry, without traces of oil.

Why is the fuel mixture supplied lean?

• lambda - the probe incorrectly informs the control unit about the amount of oxygen in the exhaust gases, the reason is sensor wear;
• faulty or clogged nozzles;
• incorrect carburetor settings or clogged fuel jets;
• insufficient pressure in the injector fuel rail;
• problems with the idle air control;
• air leakage under the manifold or in another place;
• unsuccessful chip tuning of the controller made by the owner of the car.

A lean mixture does not pose any particular danger to a running engine, but it does cause discomfort to the driver. The car accelerates slowly, pulls poorly and jerks - there is a lack of fuel. Oddly enough, the phenomenon causes increased gasoline consumption - a car enthusiast who wants to achieve better performance indicators presses the accelerator pedal harder and more often.

Note. Often the light shade of the working electrodes is explained by the type of fuel used. If the car is operated on methane or liquefied gas (propane-butane mixture), this color is considered normal.

Black soot

The most common plaque color, according to user reviews, is black. In this case, it is quite difficult to diagnose a breakdown, since there are two options for black carbon deposits, each of which indicates a problem. The main difference is the structure, which allows you to determine a group of causes of a malfunction. If you observe a uniform, grayish or coffee-colored carbon deposit, your vehicle is in full working order, the engine is running stably, without failures.

How to properly service?

It is usually customary to change spark plugs that have traveled 30-40 thousand kilometers. But few people know that candles need to be maintained. Even with a fully functional ignition system, they may not work correctly. Various deposits and oxides can form on the electrodes, which interfere with the formation of a normal spark. As the metal burns out, the gap between the electrodes increases, which also complicates the spark formation process.

To extend the life of the spark plugs, they can be cleaned. But if you just clean the white spark plugs, the effect may not be due to the increased gap between the working parts. It is necessary to restore the normal gap. Then the ignition system will work perfectly.

Oily consistency

A black deposit of an oily consistency, which is located on the surface of the thread and on the surface of the electrode, may indicate an excess of oily solution inside the VSC. Another sign is blue smoke from the exhaust pipe when starting the engine. There may be several reasons:

• the caps on the oil removal valve are out of order and worn out;
• it's time to change the rings on the pistons;
• The inner valve guide type bushings are worn out.

The main problem is a malfunction in the cylinder-piston group; parts need to be replaced.

Dry (soot type)

In this version there are no oil drips; car enthusiasts call it “velvet”. What might this accumulation indicate? One of the important reasons: a mixture of air and fuel mixed with gasoline entering the internal combustion tank. Dry coating can become a “symptom” of such serious violations:

• disrupted work process of SZ;
• there is not enough energy generated to generate the spark necessary for starting;
• insufficient compression indicators in engine tanks (cylinders).

If black velvety carbon deposits form on the SZ, experts recommend checking the compression readings inside the cylinders. For carburetor engines, the malfunction often lies in improper tuning of the carburetor. Injector - it is important to check the gasoline pressure regulator, which enriches the air mixture too much. And in these cases, increased consumption of the fuel mixture is often observed. Another common reason is contamination of the air filter, which allows a small amount of air to pass through - as a result, the fuel does not burn completely, it remains a deposit on the surface of the spark plugs. A dense black deposit tends to settle mainly on the part itself - SZ, without appearing on the thread.

Cleaning the ignition elements

Spark plugs do not always require immediate replacement; sometimes they can simply be cleaned and the possible cause of deposits can be eliminated. This procedure can be carried out in two ways:

1. Mechanical cleaning method. It consists of using simple sandpaper or a small wire brush. Despite the simplicity of the method, it has a number of disadvantages. With such cleaning, the coating on the SZ electrodes can be damaged, and simple scratches can cause increased accumulation of deposits.
2. Chemical method. It is more preferable, especially for removing black deposits. The car enthusiast will need to prepare simple cleaning products, a toothbrush and a rag. The elements need to be soaked for about half an hour and then rinsed well. After drying, the candles can be used again.

Red tint of soot

A red coating appears when the car owner uses additives for working flammable fluids. The process is characterized by the burnout of chemical impurities that are poured in large quantities. If, with constant use, the prerequisites for the formation of red accumulations appear, it is recommended to reduce additives to a minimum. This malfunction is often observed where there are impurities of chemical elements. If you do not react in a timely manner to the appearance of a coating of this color, you can allow the appearance of a serious layer of waste fluids, which can lead to expensive car repairs - a spark will not appear when starting the car. Thus, the motor will work unstably. If the problem has already appeared, you need to carefully remove the deposits, completely change the flammable liquid (drain) and switch to a different brand of gasoline.

Glossy white

This is one of the most alarming symptoms that should definitely worry the car owner - it signals that the spark plug is not cooling to the required level or the pistons are overheating, which leads to serious consequences - the car will have to be repaired, as cracks may appear in the valve - replacement of the part will cost a hefty sum. There may be several reasons:

• the amount of working fluid for cooling does not correspond to the required level;
• the fuel composition entering the internal combustion chamber is not of suitable quality;
• This results in unnecessary suction of air masses through an intake-type pipeline;
• a snag in debugging the launch - the spark is supplied very early or missed altogether;
• The SZ is not selected correctly for this motor.

If a white accumulation with traces of metal inclusions forms on the surface, it is necessary to send the car for electronic diagnostics. You should not drive your car until the problem is completely eliminated.

Other deposits on the surface of the spark plugs

In addition to the appearance of contaminants, other residues of working fluids may appear on the SZ: for example, an oil solution. In this case, malfunctions also occur when starting the car: the engine stalls after a long period of inactivity, blue-white smoke flies out of the exhaust when you first try to start it, and the level of lubricant on the dipstick decreases significantly. The malfunction may be due to broken valve caps or removable rings on the pistons themselves.

There may be traces of gasoline and coolant. In the first case, this happens due to long and unsuccessful attempts to start the car, and in the second, the working fluid, antifreeze, gets into the internal combustion chamber. To fix the problem, you need to check the cylinder head gasket. The destruction of the spark plug can be caused by a low octane number, too early ignition or problems with the spark plugs. Also, a long trip on a detonating engine plays a role. To completely eliminate the problem, it is recommended to undergo electronic diagnostics at equipped stations.

Chemical method

It is no coincidence that car owners prefer to clean elements using a chemical method. Black carbon deposits from candles can be easily cleaned using conventional cleaning products designed for cleaning tiles and plumbing fixtures. Cleaning requires a small container, a rag and a toothbrush. Having prepared everything you need, follow these simple steps:

1. Place the elements in a basin (bucket) and fill them completely with the prepared solution.
2. Leave in the solution for 30 minutes (more is possible).
3. Clean the element with a toothbrush.
4. Rinse in running water and wipe dry with a cloth.

Before putting the elements in place, you need to dry them well. To do this, place them in the oven for 20 minutes or blow them with a hairdryer at minimum power.

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