How to Diagnose Common Starting Problems

Start With What You Can Hear

Before you lift the bonnet, spend thirty seconds listening. The noise your car makes when you turn the key tells you more than any diagnostic tool. A rapid clicking sound usually points to a battery that has enough juice to fire the solenoid but not enough to turn the engine. A single heavy clunk followed by silence often means the starter motor is receiving power but not spinning. Total silence, with the dashboard lights dimming when you turn the key, suggests the battery is flat or the connections are poor. And if the engine turns over briskly but refuses to fire, you are almost certainly looking at a fuel or ignition problem rather than an electrical one. Train your ear, and you will save yourself a great deal of guesswork.

Battery Checks You Can Do in Five Minutes

The battery is the most common culprit, especially on cold mornings. Modern batteries rarely give much warning before they fail, so a quick check is worthwhile.

• Look at the terminals. White or greenish crusty deposits on the battery posts add resistance and stop current flowing properly. A stiff brush and a bit of warm water will shift them.
• Check the connections are tight. A terminal that wiggles by hand is loose enough to cause an intermittent no-start. Tighten it, but do not overdo it — you can crack a lead post.
• Listen to the cranking speed. A healthy engine turns over with a brisk, rhythmic sound. If it sounds laboured and slow, the battery is probably on its way out.
• Test the voltage. A simple multimeter across the terminals should read around 12.6 volts at rest. Below 12.2 volts means it is discharged; below 11.9 volts and it may be beyond saving.

If the car starts happily with a jump start but will not start again on its own, your battery or charging system is the problem. If it starts and then dies as soon as you disconnect the leads, suspect the alternator.

Starter Motor and Solenoid Symptoms

When the battery is sound but the engine still will not turn, the starter motor moves to the top of the list. A failing starter often gives warning signs first: a whirring noise without the engine turning, a grinding sound, or a delay of a second or two between turning the key and anything happening.

The solenoid is the small cylinder attached to the starter that pushes the gear into mesh with the flywheel. If you hear a single loud click and nothing else, the solenoid may be engaging without passing current to the motor itself. On some cars you can test this by tapping the starter body gently with a wooden handle or soft mallet while an assistant turns the key — if it bursts into life, the brushes or contacts inside are worn. This is a get-you-home trick, not a repair, so book it in promptly.

Before blaming the starter, check the earth strap between the engine and the body. A corroded earth causes all manner of strange electrical behaviour and is cheap to replace.

Fuel, Ignition and Immobiliser Possibilities

If the engine cranks strongly but will not catch, you need to work out whether it is fuel or spark that is missing.

• Fuel. Check the gauge honestly — running dry happens to the best of us. On diesel cars, a blocked fuel filter or air in the system after a filter change will stop it dead. Listen for the brief hum of the fuel pump priming when you switch the ignition on.
• Ignition. On petrol engines, worn spark plugs, damp ignition leads, or a failing coil pack can all prevent starting. Plugs are inexpensive; if yours have done more than 30,000 miles, change them.
• Immobiliser. A flashing security light on the dashboard often means the key has not been recognised. Try the spare key, check the fob battery, and make sure nothing metallic is sitting against the transponder chip.

Damp mornings are notorious for this. A spray of water-dispersing fluid on the ignition components can get you moving, though you should still replace the worn parts.

When Not to Keep Trying

There is a limit to what is sensible on a driveway. Stop cranking if you can smell petrol, if the engine is overheating, or if you have been turning it over for more than thirty seconds at a time — you will flatten the battery and risk overheating the starter. Repeating a failed start also pushes unburnt fuel into the exhaust, which can damage the catalytic converter on petrol cars, and that is an expensive mistake.

Never crawl underneath a car supported only by a jack, and be cautious around the battery: remove the negative terminal first and refit it last. If you are unsure, or the fault is intermittent and elusive, a mobile mechanic or a trusted local garage will spend less of your time and money than a trail of replaced parts.

A Sensible Order of Work

Work through it logically: listen to the noise, check the battery and its connections, then confirm whether you have fuel and spark. Nine times out of ten the answer is a tired battery, a corroded terminal, or a worn starter, all of which are straightforward to put right. Keep a cheap multimeter in the boot, keep your servicing up to date, and a non-starting car becomes a minor inconvenience rather than a crisis.