Except for diesel vehicles which do not have spark plugs, all gasoline vehicles, regardless of whether they are fuel-injected or not, have spark plugs. Why is this?

Gasoline engines suck in a combustible mixture. The spontaneous ignition point of gasoline is relatively high, so a spark plug is needed for ignition and combustion.

The function of a spark plug is to introduce the pulsed high-voltage electricity generated by the ignition coil into the combustion chamber and use the electric spark generated by the electrodes to ignite the mixture and complete combustion.

On the other hand, diesel engines suck in air into the cylinder. At the end of the compression stroke, the temperature in the cylinder reaches 500 - 800 °C. At this time, the fuel injector sprays diesel at high pressure in a misty form into the combustion chamber, where it mixes violently with hot air and evaporates to form a combustible mixture.

Since the temperature in the combustion chamber is much higher than the spontaneous ignition point of diesel (350 - 380 °C), diesel ignites and burns on its own. This is the working principle of diesel engines that can burn without an ignition system.

To achieve high temperature at the end of compression, diesel engines have a much larger compression ratio, generally twice that of gasoline engines. To ensure the reliability of high compression ratios, diesel engines are heavier than gasoline engines.

First of all, let Cool Car Worry-Free take you to understand what are the characteristics and components of a spark plug?

The model of domestic spark plugs is composed of three parts of numbers or letters.

The number in front indicates the thread diameter. For example, the number 1 indicates a thread diameter of 10 mm. The middle letter indicates the length of the part of the spark plug screwed into the cylinder. The last digit indicates the thermal type of the spark plug: 1 - 3 are hot types, 5 and 6 are medium types, and above 7 are cold types.

Secondly, Cool Car Worry-Free has collected information on how to inspect, maintain and take care of spark plugs?

1.Disassembly of spark plugs: Remove the high-voltage distributors on the spark plugs in turn and make marks at their original positions to avoid incorrect installation. - During disassembly, pay attention to removing dust and debris at the spark plug hole in advance to prevent debris from falling into the cylinder. When disassembling, use a spark plug socket to firmly hold the spark plug and turn the socket to remove it and arrange them in order.

2.Inspection of spark plugs: The normal color of the spark plug electrodes is grayish white. If the electrodes are blackened and accompanied by carbon deposits, it indicates a fault. - During inspection, connect the spark plug to the cylinder block and use the central high-voltage wire to touch the terminal of the spark plug. Then turn on the ignition switch and observe the location of the high-voltage jump. - If the high-voltage jump is at the spark plug gap, it indicates that the spark plug is working properly. Otherwise, it needs to be replaced.

3.Adjustment of spark plug electrode gap: The gap of a spark plug is its main working technical indicator. If the gap is too large, the high-voltage electricity generated by the ignition coil and distributor is difficult to jump across, making it difficult for the engine to start. If the gap is too small, it will lead to weak sparks and is prone to leakage at the same time. - The spark plug gaps of various models are different. Generally, it should be between 0.7 - 0.9. To check the gap size, a spark plug gauge or a thin metal sheet can be used. -If the gap is too large, you can gently tap the outer electrode with a screwdriver handle to make the gap normal. If the gap is too small, you can insert a screwdriver or metal sheet into the electrode and pull it outward.

4.Replacement of spark plugs: Spark plugs are consumable parts and generally should be replaced after driving 20,000 - 30,000 kilometers. The sign of spark plug replacement is that there is no spark or the discharge part of the electrode becomes circular due to ablation. In addition, if it is found during use that the spark plug is often carbonized or misfires, it is generally because the spark plug is too cold and a hot-type spark plug needs to be replaced. If there is hot spot ignition or impact sounds are emitted from the cylinder, a cold-type spark plug needs to be selected.

5.Cleaning of spark plugs:  If there is oil or carbon deposits on the spark plug, it should be cleaned in time, but do not use a flame to roast it. If the porcelain core is damaged or broken, it should be replaced.

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