Unable to Start When Hot After Shutdown but Starts Fine When Cooled Down?
2 Answers
Unable to start when hot after shutdown but starts fine when cooled down may be caused by fuel injector leakage, a faulty carbon canister solenoid valve, or fuel quality. Here are the specific explanations for the issue of being unable to start when hot after shutdown but starting fine when cooled down: Fuel Injector Leakage: Fuel injectors normally spray fuel, but leakage results in additional fuel supply. The more severe the injector leakage, the richer the air-fuel mixture becomes, leading to difficulty in starting when the engine is hot. Faulty Carbon Canister Solenoid Valve: During hot starts, fuel atomization is normally sufficient, and no additional fuel vapor is needed. If the carbon canister continues to supply extra fuel vapor to the intake manifold, it can cause an overly rich mixture, making it difficult to start. Fuel Quality: After the engine is shut down when hot, the engine compartment remains at a high temperature. If the fuel is highly volatile, it can form excessive vapor pressure in the fuel rail. When this pressure exceeds the fuel system's supply pressure, it creates vapor lock, causing the fuel injector to spray overly lean fuel vapor, resulting in difficulty starting.
I've encountered this situation quite a few times, and it's most likely caused by the crankshaft position sensor or camshaft sensor acting up. When the engine heats up, the electronic components inside these sensors expand due to overheating and malfunction. The ECU can't read the engine position signal, so of course it won't start. The fuel pump getting too hot may also lead to insufficient pressure, and there might be air bubbles trapped in the fuel system causing vapor lock. Additionally, carbon buildup in older engines can absorb fuel during warm operation, causing air-fuel ratio disturbances. For troubleshooting, the most direct method is to use a diagnostic tool to check for any interrupted RPM signal trouble codes. Alternatively, when the engine is hot, you can splash some cold water on the sensors (be careful not to wet the connectors) - if it starts immediately, that's basically confirmation of the problem.
