Why won't my car start?

A car that won't start is either not cranking (no "rrr-rrr" sound when you turn the key) or cranking but not firing. If nothing happens when you turn the key, the battery is the most likely culprit — try jump-starting. If it cranks but won't fire, the problem is fuel, spark, or compression. On modern cars, immobiliser or key fob faults can also prevent starting. The symptoms tell a lot: a slow, laboured crank points to a flat battery; clicking but no crank is usually a flat battery or bad earth; cranks fine but won't fire suggests fuel or ignition.

Do not drive

Likely causes

Likely

Flat or faulty battery

Most common cause of no-start. Jump-start to test — if it starts then dies again, the alternator may not be charging

Likely

Bad earth / ground connection

Corroded battery clamp or chassis earth strap causes intermittent starting failure — often misdiagnosed as battery

Possible

Starter motor fault

Single loud click when turning key suggests starter not engaging; whirring without cranking suggests starter pinion failure

Possible

Fuel pump or fuel delivery fault

Car cranks normally but won't fire; no fuel pressure — listen for the pump priming sound when you turn the ignition on

Possible

Immobiliser or key fob fault

Security light stays on and engine won't fire; try the spare key

Possible

Faulty crankshaft position sensor

Engine cranks but ECU has no crank signal, so it won't fire fuel or spark

Repairs you may need

Typical cost range: £40–£500Battery replacement: £80–200 fitted. Starter motor: £150–350. Fuel pump: £150–400. Earth strap: £40–100.

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Related questions

This information is a general guide based on common causes of this symptom. Symptoms can have multiple causes and accurate diagnosis requires physical inspection by a qualified mechanic. Always consult a professional before deciding not to repair.