Why is it difficult to start a diesel car after it stalls when hot?

[RiverLee]

The reasons why a diesel car is difficult to start after stalling when hot are: 1. Fuel injector leakage: Normally, the fuel injector sprays fuel, but leakage means extra fuel supply. The more severe the injector leakage, the richer the air-fuel mixture becomes, leading to difficulty in hot starts. 2. Poor fuel quality: If the fuel is highly volatile, it can form high vapor pressure in the fuel rail. When this pressure exceeds the fuel system's pressure, it creates vapor lock, causing the injector to spray overly lean fuel vapor, making it hard to start. 3. Sensor failure: The intake air temperature sensor, similar to the coolant temperature sensor, adjusts the fuel injection amount. However, if the coolant temperature sensor fails, it causes cold start issues, while a faulty intake air temperature sensor leads to hot start difficulties. 4. Engine carbon buildup: Carbon buildup is a persistent issue. It strongly adsorbs gasoline. If there's significant carbon buildup on the intake valves, throttle, or pistons, it can adsorb some fuel, resulting in an overly lean air-fuel mixture and affecting startup.

[MacCollin]

After a diesel vehicle stalls when hot, it's hard to restart. As a car enthusiast, I've encountered this situation several times. The main reason is that after the engine runs long distances and heats up, internal components like cylinder walls and piston rings expand due to heat, reducing compression pressure, which makes it difficult to ignite the diesel. Additionally, fuel in the system may vaporize due to heat, forming bubbles that block the fuel lines and prevent injection. The starter motor or battery overheating can also fail, resulting in only a clicking sound when turning the key without the engine starting. It's recommended to wait at least 15 minutes after stopping to let it cool down, or regularly check the cooling system and starter during maintenance to avoid being stranded on the road.

[IsaacAnn]

When driving my diesel car on long trips, I've encountered several instances where the engine wouldn't start after taking a break. Once at a highway service area after shutting down, it simply wouldn't start no matter what. Later, the mechanic explained that when the engine gets too hot, parts expand causing reduced compression ratio, leading to poor air-diesel mixture that can't properly compress and ignite. Another possibility is sensors getting confused by high temperatures, falsely judging that starting conditions aren't met. Now I know that during hot summers or after long drives, it's best to wait a while for the engine to cool down before attempting to restart, to avoid faster battery drain or starter motor overheating.

[Cox]

Difficulty in restarting a diesel engine when it's hot is mostly due to insufficient compression caused by internal expansion, preventing ignition; air bubbles in the fuel lines may also affect fuel supply. This is quite dangerous, especially in hot weather. I usually avoid restarting immediately after parking and check the coolant and starter first to ensure safety and avoid breakdowns. Regular cleaning of fuel injectors during maintenance can help prevent this issue.

[PeterLee]

In hot weather, the difficulty of restarting a diesel vehicle after turning it off becomes particularly evident: high temperatures cause significant expansion of engine components, leading to insufficient compression force; meanwhile, fuel is prone to vaporization, creating bubbles that block the fuel lines. As someone who frequently drives long distances, I always remind myself to wait a few extra minutes after parking to let the engine cool down and to ensure the battery is sufficiently charged to minimize the chance of malfunctions.