Cold Start Cranks But Won't Start
The engine cranks but fails to start when cold, indicating a potential issue with fuel delivery, ignition, or engine management sensors. Common causes include a failing fuel pump, weak spark, or a faulty engine coolant temperature sensor.
Diagnosis Details
Possible Causes
Failing fuel pump or fuel pressure regulator – fuel pressure drops overnight, causing hard cold starts.
Weak spark due to worn spark plugs, ignition coils, or a failing crankshaft position sensor.
Faulty engine coolant temperature sensor (ECT) – sends incorrect cold-start enrichment signal to the ECU.
Clogged fuel injectors or dirty throttle body – restricts fuel/air mixture during cold start.
Vacuum leak or intake air temperature sensor issue – causes lean mixture on cold start.
Related OBD-II Codes
Not satisfied with this diagnosis?
Try Another DiagnosisWhat To Do Next
What You Should Do
Check fuel pressure with a gauge during a cold start (should hold pressure).
Inspect spark plugs and ignition coils for wear.
Test the engine coolant temperature sensor resistance with a multimeter.
Scan for diagnostic trouble codes.
If no codes, perform a fuel system cleaning and check for vacuum leaks.
Share this diagnosis
Help others with similar symptoms
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.
