Eight Reasons Your Car Won't Start

Ellie Dyer-Brown, 3 months ago

5 min read

  • Diagnostic
  • Battery

FixMyCar discusses the problems that can prevent a car from starting.

When you rely on your car to get you from A to B every day, few things spark as strong a sense of dread as when the engine fails to start - especially if you have no idea what’s going wrong under the bonnet. This guide will help you work out what the problem is and how to fix it.


Why won't my car start?

My car won't start in the cold

My car won't start with jump leads

My car won't start but has power

My car won't start with a new battery

My car won't start right away after getting fuel

The engine cranks but my car won't start

Battery and oil light on and car won't start

The immobiliser light is on and my car won't start

Why won’t my car start?

There are many reasons why your car might fail to start. Here are the eight of the most likely causes.

1. Faulty or flat battery

A flat battery is by far the most likely reason your car won't start, and it can happen for several reasons:

  • Old age

  • Something electrical was left on, draining the power

  • Your car hasn't been driven for a long time

  • One of the components is faulty

Cold weather puts more strain on the battery, so you're more likely to encounter issues during winter. You can try jump starting the car, but even if it works, you should still get the battery checked to make sure it's in good condition.

This guide discusses how to change a car battery. The average price of a battery replacement is £217.39, according to FixMyCar's data.

2. Alternator problems

The alternator charges the battery and provides the electricity needed to run the lights, heating and radio. It can fail due to bad wiring or an issue with the drive belt. Here are five signs of a faulty alternator.

A car alternator

On average, it costs £438.61 for a repair.

3. Starter motor problems

The starter motor is connected to the battery. It gets the engine going when you turn the key or press the start button. When it stops working, you'll likely hear a loud click when you try to start the car.

Replacing a starter motor costs £308.85 on average, according to FixMyCar's data.

4. Electrical or wiring issues

Common electrical issues that can stop your car from starting include problems with the battery cables, the fuse box or the body control unit. If your car hasn't been driven for a long time, nesting rodents could have chewed through the wiring.

Fixing an electrical fault costs £64.75 on average.

5. Fuel problems

Issues with the fuel system can prevent your car from starting. These include a broken fuel pump (pictured below), a blocked fuel filter or any other mechanical or electrical problem with the system.

A fuel pump with white background

The average price of a fuel injection system repair is £185.35, according to FixMyCar's data.

6. Engine issues

Faulty mechanical components in the engine can also impact your car's ability to start. Likely culprits include the timing chain or belt and the crankshaft.

Learn more about how an engine works.

7. Faulty immobiliser

Believe it or not, your car's security system could be what's keeping you from driving anywhere. If the immobiliser doesn't recognise your key, it won't start the engine. This situation often happens because the key's battery is low and is usually accompanied by a flashing key symbol on the dashboard.

Replacing the battery should work. However, if it doesn't and you don't have a spare key, you may have to get a new one made. On average, this costs £281.76 when you book through FixMyCar.

8. Spark plugs

The final likely possibility is that the spark plugs have failed, either due to old age - they typically need replacing every 80,000 to 100,000 miles - or a flooded engine.

An old vs new spark plug.

Petrol engines sometimes flood when they are switched off too quickly after starting from cold, leaving unburnt fuel in the system, which wets the spark plugs and stops them from working. If your engine is flooded, you'll likely hear a whirring sound when you turn the key, and you may notice a strong smell of fuel.

Find out how to start a car with a flooded engine.

My car won’t start in the cold

Here are some common reasons your car won’t start in cold weather:

Try the following:

Once you’ve determined that you have the correct engine oil level and your battery looks healthy, the next option is to try jump-starting your car. Find out how here.

Failing this, call a local mechanic who can diagnose the problem and get you back on the road quickly.

My car won’t start with jump leads

There are three main reasons your car won’t start with jump leads:

In these situations, you’ll need the help of a mechanic to make your car work, unless you feel confident replacing a dead battery yourself. 

Jump Starting Car in Winter

My car won’t start but has power

If the engine turns over but won’t start, you’ve likely got a flat battery. Frequent starting problems indicate that your battery could be damaged and needs to be replaced.

Not sure what battery is right for your car? Check out this guide.

My car won’t start with a new battery

There are two possible reasons why your car won’t start with a new battery.

First, your battery hasn’t been fitted correctly, or one of the terminals is loose. This guide explains how to change a battery and can be used to check that your current battery is installed correctly.

Technician fitting a car battery.

The second is that another part, such as the alternator, is causing the problem rather than the battery.

My car won't start right away after getting fuel

If your car won't start even after you've filled up the fuel tank, it's likely due to a faulty fuel pump or fuel injectors. To test whether this is the case, try starting your car as if the engine is flooded - find out how here. If this works, there's probably something wrong with the system that moves fuel from the tank into the engine.

Don't worry; this can be easily resolved with specialist attention. FixMyCar is here to help you find a reliable local garage or even a mobile mechanic, making the process convenient and hassle-free.

The engine cranks but my car won’t start

The fact that your car can crank suggests that the problem is with the battery, which is a relatively easy fix. You may be able to solve the problem by jump-starting your car, but remember to get the battery checked to make sure it doesn't happen again.

Battery and oil light on and car won't start

In this situation, multiple issues with your car could impact its ability to start.

Firstly, check your engine oil level. If it's too low, top it up and look closely to see if you can spot any leaks. If there is a leak, you'll need to take your car to a garage as soon as possible to have it repaired.

Battery warning light

Next, check your battery. Can you see any signs of corrosion or damage? Are the terminals connected properly? If your engine turns over but won't start, you probably have a flat battery. You can try jump-starting the vehicle, but if the engine warning lights stay on, you should have it checked by a mechanic.

The immobiliser light is on and my car won’t start

There’s likely a fault with the engine immobiliser or the key transponder. You’ll probably notice that your car starts up for a few seconds only to turn off again.

In this situation, the best thing to do is to have your car’s immobiliser system looked at by a professional who can provide an accurate diagnosis and repair.

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Written by Ellie

Ellie Author Pic

Ellie is FixMyCar’s Content Writer. She has a BA in English literature from Durham University, a master’s degree in creative writing, and three years of experience writing in the automotive industry. She currently drives a Suzuki Swift.

Find Ellie on LinkedIn.