7 Reasons Why Your Car Won't Start

Is there anything more stress-inducing on a busy morning than a car that won’t start?

If you want to get to where you need to go on time, then you need to know how to diagnose a range of car issues. By knowing the possible cause, you will have a better chance at knowing how to effectively solve the problem.

Wondering why your car won’t start? This article can help you find the culprit. 

Battery Problems

If your car won’t start, then it’s not unlikely that you are suffering from a flat battery. This is particularly probable in the colder months, and could be caused by a failing alternator. A bad battery won't damage an alternator. 

Seemingly insignificant actions like not driving your car for a while or leaving the lights on can drain the battery. There could be an issue with the electrical system, or even with the battery itself if a connection is corroded. Of course, the battery itself may have simply reached the end of its life. If your car is suffering from battery problems, then you may notice that the cranking of your engine seems sluggish, or be able to hear a clicking sound when you try in vain to start your car. Your car might not make any noise when you start it, and the interior lights may fail to turn on.

You can find out if the battery is to blame by trying to jump start your car - if the jump start is successful, then the issue is probably the battery, or the alternator struggling to charge the battery. These parts may need replacing, so it would be a good idea to take your car to a garage so that a professional mechanic can advise you on what to do next. 

Alternator Problems

Another potential source of the problem, as previously mentioned, could be a failing alternator. Your car’s alternator helps to recharge the battery, and makes the lights, radio, and heating work - it is a feature of all combustion vehicles. Without it working as it should, your car is sure to run into battery problems. The battery could overheat if the alternator isn’t there to regulate the level of electricity funnelling into it. 

Lights that dim and issues with the stereo system could point towards a faulty alternator. These problems may occur as a result of wiring or computer issues, or even a blown fuse. If your alternator is failing, then you need to get this checked out and potentially replaced by a professional mechanic. You should not attempt to fix the problem yourself, as you could unintentionally electrocute yourself. 

Fuel Problems

Your fuel filter is responsible for stopping debris from making its way into the fuel system. If the fuel filter is clogged, then petrol/diesel won’t be able to reach the engine. This will make it difficult for your engine to burn fuel, explaining why starting your car has become an issue.

Other signs that your fuel filter is struggling include stalling, a rough idling noise, electric fuel pump failure, and loud noises coming from the fuel pump. If you keep driving with a clogged fuel filter, then you may even notice the sudden illumination of the check engine light. 

More simply - we’ve all done it - you may have forgotten to top up the fuel tank. Try and remember to top up your fuel levels regularly, so that you don’t cause any unwanted damage to your car. If you suspect that your fuel gauge isn’t working as it should, then it would be a good idea to have your car checked out by a professional mechanic, just to be on the safe side. A mechanic will also be able to swap your fuel filter for you, so that it is free of debris. 

AdBlue Problems

It is also worth mentioning that low AdBlue levels can prevent your engine from restarting. If you forget to top your AdBlue up when necessary, then your vehicle will enter ‘limp home’ mode, and your vehicle won’t restart after you turn the engine off.

AdBlue levels must be replenished in order for the vehicle to function, so you need to take your vehicle to a garage and have this topped up - especially if you notice the warning light whilst driving. The warning light should disappear once the AdBlue tank is full, and the ignition has been on for about a minute. If the light does not disappear, then there could be a system issue, in which case you should ask a mechanic to reset the light. You may also need to reset the dashboard after an AdBlue top-up, which you can do by referring to your vehicle handbook.

Motor Problems

Your car’s starter motor is an electrical motor powered by the battery, and it helps to start the engine. When it begins to fail, it is likely that your car won’t be able to start. Starter motor failure can be caused by such issues as loose wiring, corroded connections, bad relays, and worn-out parts.

If you try and start the engine to no avail, but notice lights on your dashboard, then there could be an issue with the starter motor. When you attempt to start your car by turning the key or pushing the start button, you should also listen for a clicking noise - this can be a sign that your starter motor isn’t working properly. You should be aware, however, that starter motors do not always give any indication that they are about to fail. 

Some other, potential more distressing signs of starter motor failure include oil leaks and smoke coming from your car. The smoke may be a result of a blown fuse, or the starter may have overheated whilst you tried to start the car. If you notice this, then call a mechanic - do not continue trying to start the car, you will only cause further damage. A faulty starter needs to be inspected by a garage, so that they can diagnose the problem and repair the part.

If you notice that your starter is covered in engine oil when you lift the hood of your car, then you likely have an oil leak. It is worth getting this checked out as soon as you can, before it evolves into a much more expensive repair. 

Engine Problems 

If there is an issue with the crankshaft or timing belt, then you may have difficulty trying to get your engine to start. There could also be problems with the fuel injectors, throttles, or the fuel pressure regulators and sensors. If your car is producing a sputtering noise, then this is a sign that the fuel system is struggling. 

As a side note, if your battery is working properly but your engine won’t start, you should turn on your headlights. As your headlights are controlled by the battery, if they turn on but the engine still won’t, then this is a sign that your ignition switch is faulty. 

Alternatively, whilst this is rare, your car could be suffering from a flooded engine. This means that there is too much fuel in the engine, and not enough air. This tends to occur when you turn your car on and off again in a short space of time - for instance, when you want to move your car to park it in a slightly different spot.

When you start your car from cold, and turn it off again soon after, unburned fuel stays in the engine and can cause damage to the spark plugs. This will make it difficult for the ignition to work, and thus the car will struggle when you next try to start it.

A strong petrol smell coming from your car’s exhaust can indicate that your engine is flooded. To find out if this is the case for your car, crank the engine with the accelerator pedal pushed down. Let the engine rev for a little while, and hold a higher idle speed for a few seconds. If your engine still does not start after doing this, then you need to have your car looked at by a professional mechanic. 

Security System Problems

Your engine immobiliser is an electronic security system designed to prevent your car from being stolen by someone without a key. This means that you will only be able to start your car if you are using the right key/fob for your vehicle. Most cars made after 1998 will have an immobiliser. 

When you attempt to get in your car, your key/fob will send an electronic signal, thus enabling the vehicle to start. This is where the immobiliser comes in, as it can disable the fuel system, starter motor, and ignition - your car’s Engine Control Unit (ECU) will not start the fuel system or the ignition circuit if the code in the key/fob does not match the one stored in the immobiliser. 

Whilst this is certainly a clever security feature, engine immobilisers can sometimes be faulty. You may experience difficulty locking or unlocking your car, have issues with the car alarm, or struggle to get the engine to start. If your car is failing to recognise your key, then you should change the battery in your fob. If this does not solve the issue, then you should refer to your vehicle handbook, or get in touch with your car's dealer for more information. 

When in doubt, an expert garage will be happy to take a look at your car, and get you back on the road with confidence in no time. 

Now that you know some of the most common reasons that cars won't start, we hope that you will be able to figure out what is wrong with your vehicle.