Why don't diesel engines use spark plugs for ignition?

[Shannon]

Because diesel fuel has a relatively low ignition temperature. Here are the relevant explanations: Working principle: Driven by the motor rotating the crankshaft, it activates the engine's crank-connecting rod mechanism, valve train, fuel supply system, etc. After intake and compression, the temperature of the compressed air at the end of compression reaches over 700 degrees Celsius. At this point, high-pressure diesel is injected into the cylinder in a mist form from the injector, and the formed mixture immediately ignites, pushing the crankshaft to continue operating. Compression-ignition diesel engine: A diesel engine directly compresses the mixture of air and fuel to the ignition point, causing it to ignite automatically, which is called compression ignition. It does not require an external spark to ignite, so it does not use spark plugs. In contrast, gasoline engines have a lower compression ratio than diesel engines and require ignition to make the gas in the cylinder combust.