Cold Start Cranks But Won't Start
The engine cranks normally but fails to start when cold, indicating a likely issue with fuel delivery, ignition, or engine management sensors. Common causes include a failing fuel pump, faulty coolant temperature sensor, or weak spark.
Diagnosis Details
Possible Causes
Fuel pump check valve failure or weak fuel pump causing loss of fuel pressure overnight
Engine coolant temperature sensor (ECT) sending incorrect cold-start signal to ECU
Faulty ignition components (spark plugs, ignition coils) or moisture in distributor/coil packs
Crankshaft position sensor or camshaft position sensor intermittent failure
Fuel injector leak or clogged injectors causing poor cold-start mixture
Related OBD-II Codes
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What You Should Do
Check fuel pressure with a gauge (should hold pressure after key off).
Test ECT sensor resistance vs temperature.
Inspect spark plugs for fouling and verify spark output.
Scan for diagnostic trouble codes.
If fuel pressure drops quickly, suspect fuel pump or check valve.
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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.
