15 different reasons why your car won’t turn over!

(Last Updated On: August 28, 2023)

A dead battery is not the only reason why your car won’t turn over, but it is the most common. If it’s not the battery, it will usually be some other form of electrical fault. However, there are instances where you will find it is not an electrical but a mechanical issue. Some of the 15 reasons for your car not starting below may be obivous to you but may not be so obvious to another, so we have included all the reasons for a car not turning over and how to fix some of them in this article.

15 Possible reasons why your car won’t turn over

1. Stuck starter motor

Inside the starter motor is a series of gears and specifically the bendix drive or the solenoid can jam especially on older vehicles. When this happens the start motor cannot turn the flywheel to start the engine, so it will not turn over, sometimes you will just hear a clicking noise when turning the key, especially when the car has a good battery or trying to jump start the car.

It may sound silly but to quickly rectify this issue you need to tap the starter motor with a large hammer, this can enough to release the blocked gears and the car will start. Rocking the vehicle forwards and backwards can also have the same effect.

The starter motor can fail altogether, so there may be a point that it actually needs replacing; this is quite a straightforward item to replace, with a bit of mechanical knowledge and a good set of tools, it can be changed at home. Have a read here for more details on how to start a car with a bad starter.

2. Immobilizer

This was more common with older cars, especially in the 90s and early 2000s, with a separate aftermarket immobilizer. An immobilizer stops the vehicle from starting until the button is pressed on the key or the fob is pressed onto a contact point on the dashboard, which disables the immobilizer and allows you to start the vehicle. When an immobilizer has failed or is working as it should, most of them restrict fuel getting to the engine, so you hear the car constantly turn over but never actually start. Immobilizers fail for many reasons, including a simple key fob battery, but they can also fall through wiring issues.

On a modern vehicle with keyless car key fobs, if the battery starts to go in the fob, you can expect a starting issue, an alarm to go off randomly, and a failure to get into the vehicle altogether. However, most modern keys have a very long life expectancy.

3. Clogged fuel filter

The fuel filter is there to catch any contaminates in the fuel before it is injected into the engine, where they could cause damage. There are several reasons the fuel filter can become clogged; the normal few are poor-quality fuel you don’t have much control over. Running very low on fuel is another; it means the contaminants that gather at the bottom of the fuel tank are pushed into the fuel filter. Lastly, a fuel filter is typically replaced as part of an annual service; if you choose not to service the vehicle, it is not replaced, so a blockage can happen. The end result is fuel is no longer passed through the fuel lines when the filter is blocked.

The only way to solve a blocked fuel filter is to replace it. This is straightforward and very cheap to do. It can be done at home on the driveaway; however, sometimes you need to bleed the fuel system afterward and need the right tools, so this might be best left to a mechanic if you don’t have the correct equipment.

4. Fuel pump

As the name would suggest, if the fuel pump becomes faulty or stops working, no fuel is pumped into the engine. The engine may start but will quickly turn off because the fuel already in the engine and injectors will ignite, but no more is forced into the engine. Fuel pumps commonly fail because of debris contamination, overheating, or the pump’s internals.

Most fuel pumps are mounted inside the fuel tank, and although reasonably straightforward to replace, the fuel system can require bleeding afterward.

5. Blocked catalytic converter

It needs to be wrong for a blocked catalytic converter to cause the vehicle not to turn over. Once a catalytic converter becomes clogged, the back pressure builds toward the engine. With no were for exhaust gasses to go except back into the intake system, no fresh oxygen is forced into the machine during the burn cycle, meaning the car cannot run.

If it got to this point, you would probably already know about it; the engine management light would be illuminated, and it would be tough to ignore. It was replacing the catalytic converter will more than likely solve the issue alone. However, it may require using a diagnostic machine to remove any fault codes and turn the EML light off.

6. No compression

It is rare that an engine will have no compression at all, but it can happen. Usually you would experience ‘ low compression’ in which the engine would run with lots of problem before it gets as bad as no compression.

Without compression the engine cannot ignite the fuel and go through its combustion cycle, so it will not start. The reasons for no compression are generally, valve related issue or a blown/leaking gasket.

A no compression related issue does require accessing the engine internals to diagnose and fix. So, not everyone will be able to repair this at home and will require a mechanic to sort it. As repairing some of the engine internals may require engine removal and a complete strip down this sort of fault can write a car off. The cost of repair can outweigh the cost of a replacement vehicle or whole new engine, obviously this is vehicle and age dependant.

7. Broken timing belt or chain

The timing or cam belt is a very sensitive part of the vehicle that needs to be replaced at intervals over the vehicle’s life. If ignored, the belt can fray, split and snap. Although this is usually when the car is already running, it can happen when you try to start the vehicle; you will never get the car started if it happens. Depending on the vehicle and how it is designed, some cars have what’s called ‘interference,’ which means when the belt snaps, the valves, and the piston collide and bend, basically an engine right off.

Vehicles with timing chains work in the same way as a timing belt; the chains can stretch or snap, which will stop you from being able to start the engine. Timing chains differ in that you don’t usually replace them until there is an issue, the are designed not to cause so much of a problem when they brake. Apart from the fact the car won’t start.

Replacing the timing belt or the chain can require special equipment, such as a cam locking tool, and you will need to understand how to time the engine. So without excellent mechanical knowledge, it will require a mechanic to change them for you.

jump start

8. Battery terminals

The battery terminals clamp to the battery via small bolt, several things can happen with battery terminals. The terminal can corrode and split or the bolt can snap which means they aren’t getting a good connection to the terminal, a poor connection means the car isn’t recieveing the full 12 volts it needs to start.

To solve this problem either replacee the bolt or the battery terminal. Terminals and the cable is available at all good parts auto stores, and is pretty easy to replace at home. Although, the ease of replacement might be vehicle specific and how to terminals bolt/clamp to the battery cable.

9. No spark

Engines require a spark delivered by the spark plug to ignite the fuel. Obviously, with no spark, there is no combustion, and thus the engine will not start. There are a couple of reasons for no spark: the coil pack has failed, or no power to the coil pack. You can have an issue such as a spark plug not gapped correctly or fouled, and the ignition leads failing. But that usually means the car will still run, and you find the engine runs rough or has a misfire.

In order to fix this kind of issue requires checking that there is 12 volts going to the coil pack, if it doesn’t fault tracing back where the 12volts should be coming from. Unfortunately, things like immobilisers can play havoc and restrict power to the ignition depending on how the immobiliser restricts it from being started.

10. Dead battery

The most obvious reason a car does not turn over is a battery with no charge. This can be for several reasons: the age of the battery and the manner in which the car was driven. I.e., A vehicle driven on lots of short journeys means the battery rarely gets fully charged and is always half empty, thus won’t last for a long time. The alternator, which sets the battery as you drive, can also become problematic, and a dead battery can be the first sign.

To rectify a dead battery, it is sometimes possible to charge it or jump-start the vehicle and keep it running to get some charge back into it. However, you may be left with no choice but to replace it. It would be wise to check that the alternator charging voltage is still between 13.4 – 14.4 volts, just to rule out the alternator as the cause for the dead battery.

11. Bad ground

Coming from the car’s battery is a positive which sends the electric current to relevant components, but the other side is the negative terminal. From the negative terminal, it is connected straight to the chassis were it acts as the earth/ground for the vehicle. A bad or poor connection to ground and the car will not turn over.

Solving bad earth requires either replacing the earth strap if necessary or just unbolting it, cleaning it with a wire brush, cleaning the area it connects to, and re-bolting it back together. One thing to note is if the ring terminal is corrupted or damaged, then it would be wise to replace the strap as manufacturers use a large gauge wire for ground, and it isn’t one you can crimp a terminal on with a set of pliers and expect to get a good ground connection.

12. Blown fuse

Fuses blow when an electricity overload flows into whichever component they are connected to. Once a fuse has blown, it will not allow the electrical current to flow until it is replaced. Fuses are a super simple item to diagnose as faulty, and replacements are necessary.

Locate the fuse box, and you can manually pull them out one at a time to inspect them. The track in the fuse will be visibly broken if the fuse is blown. You must replace the fuse with the correct size as indicated in the vehicle manual; It is strongly recommended that you don’t assume the one fitted is correct, more so on second-hand vehicles. Alternatively, you can use a test light to speed up the process if you have one.

13. Car starting procedure

Some vehicles, a Renault Megane being one of them from memory, will not start unless the vehicle is in neutral with your foot on the brake pedal. If you’re one of the people who typically leave the car in gear, you can’t start the car until you follow the car’s safety precautions. If you own the vehicle, you will likely be aware of any items, like immobilizers, and fuel pump switches, before starting the car. It is something to be mindful of, especially if you’re trying to diagnose an issue with someone else’s vehicle.

14. Jammed steering lock

This is another one that you’ll be aware of whether the steering wheel will unlock or won’t. But they can become jammed; once jammed, you will not be able to start the car until the steering lock is no longer engaged. To do this, you sometimes have to put some force onto the side of the steering wheel, very slightly trying to move the steering wheel from left to right while trying to turn the key. It can take a few times and can be a little tricky, but you rarely need to break the steering wheel lock to free it entirely, and it can be done on the key.

15. Incorrect battery

An incorrect car battery won’t happen over time, obviously; this would only come about trying to solve a battery or car starting related issue, but you must replace the battery with the correct size as recommended by the OEM. An underpowered battery will leave the vehicle struggling to turn over.

Another minor issue to be aware of when replacing the battery is ensuring the terminals are connected the right way, i.e., positive to positive. It will be apparent if incorrect as there will be sparks, and the terminals will start to melt. One other issue to point out is that an incorrect larger battery could mean the terminals can touch the underside of the car’s hood. They can arc (weld) themselves to the underside of the hood or earth themselves out on the hood, you would never get the car to turn over in this instance with the car hood shut, but it will start when the hood is open and up. It’s a stupid minor issue that can catch people out, don’t think chucking a larger battery into a car is a good thing.

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How to fix a car that won’t start?

9 times out of 10 a vehicle that won’t start is down to the battery, so usually jump starting a vehicle will work. The increased electrical load from the second battery can be enough to help with issues such as a weak alternator or weak starter motor and give you enough cranking amps to get the car started.

Unfortunately, if jump starting the vehicle doesn’t work and you can’t trace the fault to any of the above by yourself, the only option will be to get recovered to a mechanic for them to take a look.

Summary on different reasons why your car won’t turn over

A car that won’t turn over in the morning when your late for the day is a nightmare. Hopefully with the 15 reasons above you will get to the bottom of the problem. Usually, a jump start to the battery will work and if that doesn’t a gentle tap on the starter motor with a hammer, will fix any jams and get you back on the road. However, it’s wise to be mindful of other problems. If the obvious doesn’t work and it’s beyond your mechanical knowledge call a mechanic or roadside recovery will be your best bet, leave it to the professionals.

My name is Tom although my friends call me Tommy. Messing around with cars and bikes has always been a hobby of mine even from a young age. So I made it my day job 17 years ago. I am a fully qualified mechanic as you would expect. I've worked in all different areas of the motor trade, valeting, panel beating, engine repairs, I'm sure you get the idea. I enjoy sharing my wealth of knowledge and experience with others, which is the reason I spend a lot of time here writing for this website.

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