What are the main reasons for difficulty starting a hot engine?

[DelSebastian]

The main reasons for difficulty starting a hot engine are as follows: 1. Fuel injector leakage. While fuel injection is normal operation, leakage constitutes additional fuel supply. The more severe the injector leakage, the richer the air-fuel mixture becomes, leading to difficulty starting when the engine is hot. 2. Damaged carbon canister purge valve. During hot starts, fuel atomization is already normal and no additional fuel vapor is needed. If the carbon canister continues to supply fuel vapor to the intake manifold, it will cause an over-rich mixture, making starting difficult. 3. Poor fuel quality. After the hot engine is shut off for a period, the engine compartment remains at high temperature. If the fuel is highly volatile, it can create excessive vapor pressure in the fuel rail. When this pressure exceeds the fuel system pressure, vapor lock occurs, causing the fuel injectors to deliver overly lean fuel vapor, resulting in starting difficulties.