The high - voltage current generated by the truck's ignition system passes through the central electrode of the spark plug. A high - voltage difference is formed between the central electrode and the ground electrode. When the voltage is strong enough, the originally insulated air between the electrodes is broken down, generating a spark. This spark ignites the air - fuel mixture in the engine's combustion chamber. The mixture explodes and burns, pushing the piston to move, thus making the engine run and providing power for the truck.

(1) Classification by Shape

There are standard - type, projected - insulator - type, multi - electrode - type, seat - type, fine - wire - type, and surface - discharge - type spark plugs, etc. For example, the standard - type is widely used in ordinary gasoline engines; the fine - wire - type has concentrated ignition, which can enhance the ignition speed and energy, making it suitable for engines with high ignition requirements.

(2) Classification by Heat Value

Cold - type spark plugs have a short skirt, with strong heat - conduction ability, and are suitable for high - compression - ratio and high - speed engines. Hot - type spark plugs have a long skirt, with weak heat - dissipation ability, and are suitable for low - speed and low - compression - ratio engines.

(3) Classification by Electrode Material

Nickel - alloy spark plugs are affordable but have a relatively short lifespan. Precious - metal - based spark plugs, such as yttrium - based, platinum - based, iridium - based, and platinum - iridium alloy spark plugs, have better corrosion resistance and electrical conductivity, and a longer service life. They are suitable for high - end trucks or users with strict performance requirements.

The average lifespan of ordinary copper - core spark plugs is generally 20,000 - 30,000 kilometers. Platinum - based spark plugs can last for 40,000 - 60,000 kilometers, and iridium - based spark plugs can last for 60,000 - 90,000 kilometers. However, the actual lifespan is affected by various factors such as driving conditions, driving habits, fuel quality, and the working state of the engine. Harsh working conditions or the use of low - quality fuel will shorten their lifespan.

(1) Correct Installation

When installing spark plugs, be sure to use special tools and tighten them according to the specified torque. If it is too loose, it will cause air leakage and poor ignition, affecting the engine's performance. If it is too tight, it may damage the spark plug or the threads of the cylinder head. Also, ensure that the spark plug model is fully compatible with the engine. Different models of spark plugs have different parameters such as electrode gap and heat value. Incompatible spark plugs will seriously affect the normal operation of the engine.

(2) Daily Maintenance

Regularly clean the carbon deposits and oil stains on the surface of the spark plugs. Special spark plug cleaners can be used. Excessive carbon deposits will reduce the ignition performance of the spark plugs, resulting in difficult engine starting and decreased power. In addition, during the regular maintenance of the truck, check the wear condition of the spark plug electrodes and the gap size. If the electrodes are severely worn or the gap does not meet the standard, adjust or replace them in a timely manner.

(3) Coping with Special Working Conditions

When the truck is driving in high - altitude areas, due to low air pressure and thin air, the engine's combustion conditions change. At this time, the ignition advance angle of the spark plug can be appropriately adjusted to ensure normal engine combustion. In cold areas, low temperatures will deteriorate fuel atomization. Spark plugs with a slightly lower heat value can be selected to improve ignition performance and help the engine start smoothly.