What are the troubleshooting methods for difficult hot-starting?
2 Answers
Troubleshooting methods for difficult hot-starting: 1. Ignition coil failure: When experiencing difficulty in hot-starting, inspect the vehicle's electrical circuit. If there is a noticeable difference in the intensity of high-voltage sparks between cold-start and hot-start conditions—with strong blue sparks during cold-start and weak reddish sparks during hot-start—it can be determined as an ignition coil failure. When the insulation capability of the ignition coil deteriorates, local short circuits occur due to temperature effects, weakening the high-voltage spark intensity. Additionally, as the ignition coil temperature rises, its resistance increases, reducing the induced voltage and further weakening the spark, making it difficult to ignite the air-fuel mixture, resulting in difficult hot-starting. 2. Vapor lock causing hot-start difficulty: This phenomenon may occur in some vehicles during prolonged summer driving. After high-speed driving, the engine temperature becomes very high, especially in summer. If the engine suddenly stalls and the throttle is closed, cold air is no longer drawn in, and poor ventilation under the hood makes heat dissipation difficult, causing the carburetor temperature to rise even higher than during driving. Consequently, gasoline evaporates rapidly. During a hot-start, very little cold air is drawn in, creating an overly rich air-fuel mixture. The engine primarily draws in gasoline vapor accumulated at the carburetor inlet, making it impossible to start. If the intake air automatic preheater's thermal switch functions correctly, minimizing intake air heating and supplying air to the intake manifold, an ideal air-fuel mixture can be achieved according to the carburetor's function, overcoming the issue. If the automatic preheater malfunctions, occasional hot-start difficulties may occur.
I encountered the issue of difficult hot starts with my car last month, which was quite annoying, but I managed to fix it myself. Generally, you should check the spark plugs for carbon buildup or wear, as this can cause weak ignition. If the spark plugs are fine, inspect the air filter—sometimes excessive dust can block the intake, making the engine struggle to breathe. Additionally, the fuel system is crucial. For example, a leaking fuel pressure regulator or faulty fuel injectors can be checked by testing the fuel pump pressure. A malfunctioning temperature sensor can also cause the ECU to incorrectly adjust the air-fuel mixture, and these issues often surface during hot starts. My advice is to start with simpler checks, like replacing spark plugs or the air filter, and leave more complex problems to professionals. Regular maintenance, such as cleaning these components, can help prevent such failures. Remember, ignoring starting difficulties can damage the engine, so don’t delay.
