It can be worrying – and not to mention inconvenient – if your car won’t start. But why do cars sometimes fail to start up?
Find out the top 11 most common reasons why you might have trouble starting your car. We’ll also give you some tips for diagnosing problems by the type of sound your vehicle makes when you turn the key (including clicking noises and engine cranking).
If your car still won’t start after reading this article, give us a call on 03330 046 046 and we’ll be able to help.
In this article:Why your car won’t startDiagnose starting problems |
Why won't my car start?
1. Flat, faulty or dead battery
The battery is usually the main reason that your car won't start, and is one of the most common callouts to the AA.
There are a few ways your battery might go flat or even die:
- Something electrical was left on in the car, like the lights, which ran the battery down.
- You haven’t driven your car for a long time.
- A fault with one of the battery components.
If the car makes a rapid clicking sound when you turn the key but won’t start, it could be the battery. A jump start might get you going again but you may need to replace the battery or have our battery assist team check the electrical and charging systems.
Battery problems are particularly likely to happen in cold weather, when the battery gets cold and struggles to hold its charge.
Dead car battery?
Battery Assist can help.
2. Starter motor problems
Some of the cars we're called out to that won’t start have a problem with the starter motor. The starter motor is connected to the car’s battery and sets the engine in motion when you turn the key or press the start button.
A symptom of a faulty starter motor might be a loud click when you turn the key in the ignition. If there’s a problem with the starter motor, a mechanic will need to check it along with the car’s electrical system. Get breakdown cover with us and you'll be able to call us out for starter motor problems.
3. Fuel problems
Fuel problems are fairly common for cars that won’t start.
That includes issues with the fuel pump, as well as electrical or mechanical issues with the fuel system.
If you’ve put the wrong fuel in, AA Fuel Assist can help.
4. Electrical or wiring problems
Electrical problems in non-starting cars include issues with the fuse box, with battery cables or with the body control unit.
Remember that rodents can nest under the bonnet of your car and gnaw the wiring if it hasn’t been driven for a while.
5. Engine problems
Problems with the mechanics of your car’s engine can stop the car from starting. The main culprits are usually the crankshaft or the timing belt and timing chain.
This could be the root cause of your problem if the engine turns over more quickly than usual.
6. Faulty immobilisers
Sometimes, your car’s security system might actually stop you from starting the car if it doesn’t recognise your key. This might be because the battery in your key fob is low. You may notice a flashing key symbol or rapidly flashing light on your dashboard. Try holding your fob right against the start button or try a spare key. If it’s still not working or you don’t have a spare, you might need to get a new key.
Find out about our key replacement service.
7. Alternator problems
Alternator problems include issues with the alternator drive belt and the wiring.The alternator creates the electricity needed to operate the lights, radio and heating. It also charges the car battery.
8. Engine intake issues
Problems with the engine intake include faulty fuel injectors, throttles, and fuel pressure regulators and sensors. If you struggle to start the car and have also noticed a whining or sputtering from the car recently, it could be a problem with the fuel system.
9. Jammed ignition or steering lock
If you can’t turn the key in the ignition, the steering lock might be jammed.
This can be caused by a wheel pressing hard against a kerb or by parking with the steering wheel in full lock.
You can try these steps to free it up:
- You should be able to move the steering wheel slightly with the steering lock on.
- Try to find the free-play area by rocking the steering and see if the key will turn at this point.
- Sometimes it’s easier to do with 2 people.
- Don’t try to force the key or it may break.
You can often free a jammed lock yourself without needing a mechanic.
10. Spark plugs
Our mechanics see hundreds of cars every month that won’t start due to issues with the spark plugs.
A common issue is a flooded petrol engine. This happens when the engine’s switched off too soon after being started from cold. The unburned fuel which entered the engine remains there after you turn if off. That wets the spark plugs and makes it hard to restart the car.
It could be a flooded engine if you hear a very fast cranking sound when you turn the key (usually a 'whirring' sound). You might also notice a strong smell of petrol or the car may start briefly and cut out again.
Find out more about flooded petrol engines.
11. Low AdBlue
If you’ve run out of AdBlue, you won’t be able to restart the engine. You may have to call out a mechanic as some car models need software to restart them.
It’s easy to avoid running out though – your car will show you a warning with a countdown on the dashboard to give you time to top up.
We provide 24/7 roadside assistance.
Diagnose starting problems
Sometimes you can get a clue about what’s wrong with your car from what happens when you try to start it.
No noise when starting the car
This could be a problem with your battery’s connection.
Rapid clicking noise when you start the ignition
This usually indicates a problem with the electrical system. It could be:
- Flat or low battery
- Alternator problem
Single click when you start the ignition
This is usually a problem with the starter or starter relay (the switch which transmits power to the starter). It could also be an electrical circuit issue, such as a bad earth connection.
Engine cranks but car won’t start
This is often a fuel problem. It might be caused by:
- Flooded engine
- Empty fuel tank
- Blocked fuel filter
- Faulty fuel pump
Engine starts but cuts out
This could be caused by:
- Fuel injection or carburettor problem
- Flooded engine (if you also notice a strong petrol smell)
- Immobiliser fault
What do I do if my car won't start?
A car not starting can be a major inconvenience. Sometimes it will be down to an issue that you can solve yourself, like a jammed ignition lock or steering (see above on this page), however, you’ll usually need to call out a trained mechanic for assistance.
If you’re already a member simply let us know that your car won’t start and we’ll send a mechanic. Please note that if your car is within 1/4 mile of your home, you’ll need to have the optional At Home cover as part of your package.
Who can I call if my car won't start?
If you need breakdown assistance but you’re not a member with us, you can call 03330 046 046 and we’ll be able to help.
How to jump start your car
If you have trouble starting your car and think it’s a flat battery, you might be able to use a jump start to get you going again.
You’ll need to use a pair of jump leads to connect your battery to another car’s battery which is fully working. However, we always recommend calling an expert first – if you're signed up for breakdown cover with us or your car won't jump start, we can assist.
Find out how to jump start a car.
If your car won't start you can call us for instant breakdown cover.
How do I know if my starter fuse is blown?
If your car is struggling to start, there are some signs to look out for that a starter fuse has blown or is in bad condition, including some common symptoms such as:
- Nothing at all happens when you turn your ignition key or ignition button, and the engine isn’t turning over.
- You can see smoke coming from under the bonnet
- You may be able to see visible damage to your car’s fuse box – though we’d recommend not checking this yourself. Always get a trained mechanic to take a look.
Why won't my car start but the radio and lights work?
There could be a number of things wrong if your car won’t start but the lights come on, largely depending on what noises you hear when trying to start the ignition. If you don’t hear anything at all, it could be a problem with the ignition switch and fuse, the starter solenoid, or bad electrical systems in your car, to name a few.
If you can hear a clicking noise, you may have a partially discharged battery or a damaged starter motor. In any case, the best thing you can do is to call out a mechanic who will be able to diagnose the problem for you and get you back on the road.
Help for a breakdown at home
If your car won’t start at home, don’t keep turning the key for a long period of time as this could cause damage. It’s best to ask a mechanic for help.
With our At Home breakdown cover, we’ll come right to your doorstep and try to get you going again.
Find out how to avoid a breakdown – car maintenance tips
Why choose us?
- We're a Which? recommended breakdown cover provider in 2023 – the sixth year running.
- UK drivers have consistently rated us as the best breakdown service against all other major breakdown providers.
- Our Patrols will usually get to you in less than an hour and get you back on the road in around 30 minutes of arrival.
Verify at theAA.com/best.
FAQs
Why won't my car start but I have power?
If you attempt to start up your car but the engine won’t turn over and the dashboard lights up, then you most likely have an issue with your battery. You could have a damaged or corroded battery terminal, which is stopping the engine from starting up when you fully turn the key.
Alternatively, make sure your clutch is fully depressed when turning the ignition key if your car is a manual – it may be that the clutch has a safety switch. On automatic cars, make sure you’re in park or neutral and the brake pedal is pressed before trying to start the ignition.
Why won't my car start but the battery is good?
If your car won’t start but the battery is good, the most common cause is a faulty starter – though it could also be to do with your fuel. You may have insufficient fuel to get the car going.
How do you tell if it's your starter or your battery?
If your car won’t start and you want to diagnose whether it’s a starter or battery problem, try listening to the engine when you attempt to start the car. If the dashboard lights come on but you hear awkward engine noises like clicking or whirring, then it’s most likely a starter problem, as the battery is providing enough current for certain parts of the car to work.