Why does the car fail to start when hot but starts immediately when cold?

[StElaina]

The reasons why a hot engine fails to start while a cold one starts immediately: Carbon deposits: At high temperatures, carbon deposits have a strong adsorption effect on gasoline. If there are excessive carbon deposits on intake valves, throttle valves, pistons, etc., they tend to absorb some fuel, resulting in an overly lean air-fuel mixture that affects starting. Coolant temperature sensor: The coolant temperature sensor plays a role in adjusting fuel injection pulse width. If it malfunctions and fails to provide correct temperature signals, it will affect engine fuel injection, easily causing abnormal air-fuel ratios in the mixture and hindering startup. Intake air temperature sensor: Similar to the coolant temperature sensor, the intake air temperature sensor also adjusts fuel injection quantity. Higher intake air temperatures lead to richer mixtures, while open circuits or poor grounding of this sensor can cause overly lean mixtures. Both overly rich and lean mixtures can make starting difficult. Fuel quality issues: After a hot engine shutdown, the engine compartment remains at high temperatures. If the fuel itself is prone to evaporation, it can form high vapor pressure in the fuel rail. When this pressure exceeds the fuel system pressure, vapor lock occurs, causing overly lean fuel vapor injection from the injectors and making starting difficult. Fuel injector leakage: Due to the high residual engine temperature after shutdown, leaking fuel turns into vapor entering the intake manifold. Hot starts under these conditions create an overly rich mixture, making starting difficult.