Car will not start? Understand the symptoms first

Cranking is the engine being turned by the starting system before it begins running under its own power. Three descriptions help separate a starting complaint: nothing turns, the engine turns unusually slowly, or it turns at its usual speed but does not begin running. These are observations, not diagnoses. Describe which one you noticed rather than using flat battery to describe every unsuccessful start. Conventional engine starting is the focus here; hybrid and electric vehicle start-up procedures can be different.

DENSO includes battery condition, cables, connections and the starter control circuit in a starting-system investigation. Clicking or slow rotation can have more than one explanation. A useful assessment checks whether power reaches the starter correctly under the relevant conditions, rather than choosing a replacement from the sound alone. Test limits belong to the particular vehicle and its repair information; a generic voltage number is not a diagnosis.

If the engine is being turned normally, explain that clearly. The investigation may extend beyond the battery and starter to other systems needed for the engine to run. RAC's no-start guidance includes fuel and security-system issues among several possibilities. Note any message already displayed and whether the engine briefly started then stopped. Do not bypass an immobiliser, bridge a starter or repeatedly operate the starting system to prove the symptom.

Compare two descriptions: the starter is broken, and the engine turned slowly on the first attempt after being parked overnight; the dashboard then showed a warning. The second preserves what was actually observed and leaves the cause open for testing. If an earlier battery test, recharge or repair has already been done, retain its result and date. Do not repeat a failed start just to obtain a recording.

• Vehicle model and the last time it started normally.
• No rotation, unusually slow rotation, or normal rotation without running.
• Warning wording and any clicking or other sound already noticed.
• Recent battery, accessory or starting-system work.

Ask whether the battery was ready for testing, whether the supply and return connections were checked, and what finding justifies any proposed starter replacement. DENSO also identifies mechanical conditions as possible contributors to cranking problems. If the symptom did not appear during the visit, keep that limitation in the record. A normal start on one occasion does not explain a recurring failure. Follow the vehicle handbook and arrange appropriate assistance if you cannot start safely.

Related guidance from motoring organisations and equipment manufacturers. Use the instructions for your exact vehicle and equipment when making a decision.

• DENSO: Starter troubleshooting
• RAC: My car will not start