Spark Plug Function and Working Principle
Release Time:
May 26,2026
Spark Plug Function and Working Principle
I. Core Function
The spark plug is a key component of the ignition system in a gasoline engine. Its function is to receive high voltage electricity, generate an electric spark in the engine cylinder, ignite the fuel and air mixture, and drive the piston to do work, thereby providing power for the engine. In a diesel engine, there is no spark plug; it relies on compression ignition.
II. Basic Structure
It mainly consists of a terminal nut, an insulator, a central electrode, a side electrode, and a housing. There is a small electrode gap (typically 0.6 - 1.1mm) between the central electrode and the side electrode.
III. Working Principle
High-voltage power supply: The ignition coil boosts the low-voltage electricity to tens of thousands of volts of high voltage electricity and transmits it to the center electrode of the spark plug.
Breakdown discharge: The high voltage electricity breaks through the air insulation of the electrode gap and forms an arc electric spark.
Ignition combustion: The electric spark instantly ignites the compressed gasoline + air mixture in the cylinder, causing the mixture to combust vigorously and expand.
Power output: The gas pressure pushes the piston downward, driving the crankshaft to rotate, completing the engine's power generation cycle.
Cycle reset: After a single ignition, the electrodes cool down, waiting for the next ignition command, and this process repeats.
IV. Additional Points
The electrode gap directly affects the ignition strength: A too small gap results in weak sparks and easy carbon buildup; a too large gap leads to spark failure and difficulty in starting.
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