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.

[OAniyah]

I encountered a situation last week where the car wouldn't start when hot. I was driving out for errands, and after stopping briefly, it just made a whining sound without responding when I tried to restart. This issue is particularly common in summer, possibly because the engine compartment gets too hot, causing increased fuel evaporation and an overly rich air-fuel mixture that affects the ignition system. Additionally, components like the intake air temperature sensor can malfunction when overheated, sending incorrect signals to the car's computer and misleading the starting process. Sometimes, the starter becomes sluggish in high temperatures, or the spark plugs are old and heavily carbon-fouled, failing to ignite. I remember checking the battery connections that time—they weren't loose—but later, when towed to the repair shop, it turned out to be an issue with the camshaft position sensor. My advice is not to panic if this happens; first, wait a bit to let the car cool down slightly and try again. If it still doesn't work, get it repaired promptly to avoid being stranded on the road.

[LaMiles]

Hot-start failure is quite annoying. As a seasoned driver, I've identified several key causes: First, faulty electronic sensors like the camshaft position sensor or intake air temperature sensor malfunctioning under high heat, causing the ECU to make incorrect judgments. Second, an overheated starter motor becoming sluggish or stuck. Third, fuel system issues where gasoline evaporates too quickly in high temperatures, creating excessive vapor that disrupts the air-fuel ratio. Fourth, a weak battery that's more prone to insufficient discharge in hot weather. For troubleshooting, start with the basics: check for loose battery terminals and listen for abnormal starter sounds. If it happens frequently, inspect the sensors and fuel pump. Ignoring this issue can damage engine components - regular maintenance should include cleaning heat-accumulating areas in the engine bay.

[SanSebastian]

My new energy vehicle also experiences difficulty starting when hot, but most hot-start failures are due to defects in the electronic control system. When the engine is hot, certain sensors such as the crankshaft position sensor may give false readings under high temperatures, causing ignition timing errors; or the starter motor coils may fail due to heat. Additionally, gasoline has higher volatility in hot weather, which can lead to an overly rich air-fuel mixture that fails to ignite. For simple troubleshooting, let the car cool for a few minutes before attempting to start again; if the problem persists, check for spark plug carbon buildup or unstable battery voltage. If this issue occurs frequently, consider upgrading the ECU software or replacing related components.