What Are the Reasons for Difficult Hot Start of a Pull-Start Gasoline Engine?
2 Answers
1. Fuel injector may be leaking: While normal fuel injection is fine, leakage constitutes extra fuel supply. The more severe the injector leakage, the richer the air-fuel mixture becomes, leading to difficulty in hot starts. 2. Engine carbon buildup: Carbon buildup in the engine is a persistent issue. Carbon has a strong adsorption effect on gasoline. If there is significant carbon buildup on the intake valves, throttle, or pistons, it can easily adsorb some fuel, causing the air-fuel mixture to become too lean and affecting startup. This issue can also occur during cold starts. 3. Poor fuel quality: After a hot engine is shut down for a while, the engine compartment remains quite hot. If the fuel is highly volatile, it can form high vapor pressure in the fuel rail. When this pressure exceeds the fuel system's supply pressure, it creates vapor lock, resulting in overly lean fuel vapor from the injector and making startup difficult. 4. Intake air temperature sensor issue: The intake air temperature sensor is similar to the coolant temperature sensor in that both adjust fuel injection. However, if the coolant temperature sensor fails, it causes difficulty in cold starts, whereas a faulty intake air temperature sensor leads to difficulty in hot starts.
I have been repairing small gasoline engines for many years and often encounter difficulties with hot-starting pull-cord gasoline engines. The most common issue is the formation of vapor lock inside the carburetor when the engine is hot, where fuel vapor blocks the fuel supply, leading to poor combustion and ignition failure. Additionally, spark plugs are prone to carbon buildup under high temperatures, causing ignition failure. The compression ratio may also decrease due to thermal expansion, resulting in piston ring leakage and poor sealing. Another issue is clogged air filters, which reduce airflow when the engine is hot, disrupting the air-fuel mixture ratio and causing ignition difficulties. It is recommended to check the cleanliness of the spark plugs, clean the carburetor fuel passages, and inspect the air filter for blockages after the engine has cooled down. Safety reminder: Hot engine parts can cause burns—avoid touching them. Maintain a steady rhythm when pull-starting to avoid excessive force that could damage the engine. Regular maintenance, such as quarterly cleaning of components, can significantly reduce the occurrence of such problems.
