Engine Cranks But Won't Start When Warm
The engine cranks normally but fails to start when warm, indicating a potential fuel or ignition issue that is temperature-sensitive. Common causes include a failing fuel pump, faulty crankshaft position sensor, or vapor lock.
Diagnosis Details
Possible Causes
Faulty crankshaft position sensor (CKP) – fails when hot, losing signal to ECM
Fuel pump or fuel pump relay failing when warm – loss of fuel pressure
Vapor lock in fuel system – fuel boils in lines causing air pockets
Related OBD-II Codes
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What You Should Do
Check for spark and fuel pressure when engine is warm and won't start.
Test crankshaft position sensor resistance and signal.
Inspect fuel pump relay and listen for pump prime.
If no spark, suspect CKP sensor; if no fuel pressure, suspect pump or relay.
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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.
