Engine Cranks But Won't Start When Warm
The engine cranks normally but fails to start when warm, indicating a likely fuel or ignition issue that prevents the engine from firing after it has reached operating temperature.
Diagnosis Details
Possible Causes
Faulty engine coolant temperature sensor (ECT) sending incorrect warm signal to PCM, causing overly lean fuel mixture
Weak fuel pump or failing fuel pump driver module, losing pressure when hot
Crankshaft position sensor failing due to heat expansion
Vapor lock in fuel system (less common on modern EFI but possible with extreme heat or aftermarket modifications)
Related OBD-II Codes
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What You Should Do
Check for diagnostic trouble codes (DTCs) first.
Monitor live data for ECT sensor reading when engine is warm (should match intake air temp).
Test fuel pressure during hot cranking (should be 55-65 psi).
Inspect crankshaft position sensor connector for heat damage.
If no codes, perform a fuel pressure leak-down test and check for spark at the plugs when warm.
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Disclaimer: This AI-generated diagnosis is for informational reference only. Always consult a qualified mechanic for an in-person inspection. AutOwner is not responsible for decisions made based on this information.
