A dead battery is not the only reason your car won’t turn over; of course, it is the most common. But what if it’s not the battery?
There are instances where you will find it’s either an electrical or mechanical fault, which might take more work to determine the cause. So, I’ve put together this list of 15 reasons your car won’t start to point you in the right direction. Depending on the symptoms, they won’t all be relevant to your vehicle.
16 Reasons Why Your Car Won’t Turn Over
The list of 16 different reasons might not all be relevant to your circumstances but by knowing how and why each component fails, you can go through and check each component, ruling them out.
Empty gas tank
For obvious reasons without any gas in the tank the car will not start. The AA attend over 10,500 breakdowns every year where the problem is just no fuel. Nothing more needs to be said other than, if you car won’t start, double check you car has fuel. Don’t just rely on the gauge because if that is reading wrong, you’ve found your problem.
Stuck starter motor
Inside the starter motor is a series of gears, a Bendix drive, and a solenoid. The Bendix drive and solenoid can stick, 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 hear a clicking noise when turning the key, especially when the car has a good battery.
It may sound silly, but to quickly rectify this issue, you need to tap the starter motor with a large hammer; this can be enough to release the blocked gears, and the car will start. Rocking the vehicle forwards and backward can also have the same effect.
The starter motor can fail altogether, so there may be a point that it 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.
Immobilizer
This was more common with older cars, especially in the 90s and early 2000s, with separate aftermarket immobilizers. 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. This turns off the immobilizer and allows you to start the vehicle. Most immobilizers work by disabling the fuel pump, so with a failed immobilizer, fuel cannot reach the engine, so you may hear the car constantly turn over but never actually fire up. 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 key fobs, if the battery starts to go in the fob, you can expect a starting issue, the alarm to go off randomly, and you may fail to get into the vehicle altogether. However, most modern key batteries have a very long life expectancy.
Clogged fuel filter
The fuel filter is responsible for trapping any harmful particles or impurities present in the fuel before it reaches the engine. There are several reasons why the fuel filter can get clogged; the most common one is the usage of low-quality fuel, which is beyond your control. Another reason is running the vehicle on very low fuel, which forces the impurities at the bottom of the fuel tank to get into the fuel filter.
Lastly, a fuel filter is typically replaced during an annual service, but if you choose not to service the vehicle, the filter is not replaced, eventually leading to blockages. The consequence of a clogged fuel filter is that the fuel cannot pass through the fuel lines, leading to engine performance issues.
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, which requires the right tools, so this might be best left to a mechanic if you don’t have the correct equipment.
Fuel pump
If the fuel pump stops working, no fuel will be pumped into the engine. Even though the engine may start initially, it will quickly turn off because no more fuel will be forced into the engine. Fuel pumps can fail due to debris contamination, overheating, or issues with the pump’s internals.
Most fuel pumps are located inside the fuel tank, and while replacing them is usually straightforward, the fuel system may require bleeding afterward.
Blocked catalytic converter
It needs to be severe for a blocked catalytic converter to cause the vehicle not to turn over, so it’s not that common, but it does happen. Once a catalytic converter becomes clogged, the back pressure builds toward the engine. With no place for exhaust gasses to go except back into the intake system, no fresh oxygen is forced into the motor during the burn cycle, meaning the car cannot run.
If it got to this point, you would already know about it; the engine check engine light would be on, and it would be tough to ignore. Replacing the catalytic converter will likely solve the issue alone. However, it may require using a diagnostic machine to remove any fault codes and turn the EML light off.
No compression
An engine rarely has no compression, but it can happen. Usually, you would experience ‘ low compression,’ in which the engine would run with lots of problems before it got 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 issues or a blown/leaking gasket.
A no compression-related issue does require accessing the engine internals to diagnose and fix. So, not everyone can repair this at home, and a mechanic will be needed to sort it. 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 repair cost can outweigh the cost of a replacement vehicle or a new engine.
Broken timing belt or chain
The timing or cam belt is a sensitive part of the engine 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 ‘interference,’ which means when the belt snaps, the valves and pistons collide, bending the valves, 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 because you usually replace them when there is an issue; they are designed not to cause so much of a problem when they break. 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.
Battery terminals
The battery terminals clamp to the battery via a 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 battery; a poor connection means the car isn’t receiving the full 12 volts it needs to start.
To solve this problem, either replace the bolt or the battery terminal. Terminals and cables are available at all good auto parts stores and easily replaced at home. However, please be aware that some terminals and cable thicknesses are vehicle-specific.
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 common reasons for no spark:
- The coil pack has failed.
- There is no power to the coil pack.
- Spark plugs are not gapped correctly or fouled.
- The ignition leads failed.
If you get the car started, you may also find the engine has a misfire with these faults.
Fixing this issue requires checking that 12 volts are going to the coil pack; if not, trace back to where the 12 volts should be coming from. Unfortunately, things like immobilizers can play havoc and restrict power to the ignition depending on how the immobilizer hinders it from being started, so bear in mind that it might actually be an immobilizer fault.
Dead battery
If your car fails to turn over, it’s usually because the battery is dead. This can happen because the battery is old or the vehicle was only driven for short distances, which means the battery never gets fully charged.
If the battery is dead, it’s possible to charge it or jump-start the vehicle to get some charge back into it. However, if the battery is too old or damaged, it may need to be replaced. To avoid this, it’s a good idea to check the charging voltage of the alternator, which charges the battery as you drive. If the voltage is between 13.4 and 14.4 volts, the alternator is probably not the cause of the dead battery.
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, where it acts as the earth/ground for the vehicle. A bad or poor connection to the 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 corroded or damaged, 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.
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 simple items to diagnose as faulty, and replacements are necessary.
Locate the fuse box, and you can manually pull them out individually to inspect them, or if you have one, use a fuse test light to speed the process up. The track in the fuse will be visibly broken if the fuse is blown. As the vehicle manual indicates, you must replace the fuse with the correct size. I strongly recommend you refrain from assuming the fitted one is correct, especially on second-hand vehicles.
Car starting procedure
Some vehicles, a Renault Megane being one of them from memory, will only start if the car 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 only start the car once 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.
Engaged steering lock
This is another one that you’ll be aware of whether the steering wheel will unlock or won’t. But steering locks can get stuck; once jammed, you cannot 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 be tricky, but you rarely need to break the steering wheel lock to free it.
Incorrect battery
An incorrect car battery won’t happen over time; this would only come about when trying to solve a battery or car starting-related issue. However, as the OEM recommends, you must replace the battery with the correct size. 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 correctly, i.e., positive to positive. It will be apparent if it is incorrect as there will be sparks, and the terminals will start to melt.
Lastly, I once experienced going out to look at a car with this, which I can tell you was pretty embarrassing for the customer; they had fitted an incorrect larger battery, and the terminals were touching the underside of the car’s hood. The terminals were earthing themselves out on the bottom of the hood. You would never get the car to turn over in this with the car hood shut, but it will start when the hood is open and up. Chucking a larger battery into a car will not make it last longer.
How to Fix a Car That Won’t Start?
Nine times out of ten, a vehicle that won’t start is down to the battery, so jump-starting the car will usually 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
A car that won’t turn over in the morning when you are late for the day is a nightmare. Hopefully, with the 16 reasons above, you will get to the bottom of the problem. Usually, a jump start to the battery will work; if that doesn’t, a gentle tap on the starter motor with a hammer will fix a stuck gearing 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.
