When your engine turns over but won’t start, it means the engine is having a hard time creating a spark, producing compression, or receiving fuel. If you hear the engine turning over, the problem has to do with the starting motor system, not the engine itself.
Various reasons are causing your engine not to start even after turning over, including an issue with the ignition, the fuel filter, or other issues controlling the engine cylinders' mechanical performance.
This article serves as a guidance to troubleshoot engine turning but not starting problem. The guidance is meant to help you identify the problem, not resolve it. Understanding the root problem helps you whether you need a professional mechanic to repair your vehicle or do it yourself.
Six possible reasons for your engine turns over but won’t start
When your engine turns over but won’t start, the problem is either related to the starter system, the fuel system, or the operation of the engine itself. Here is all that you need to check in order:
Check your fuel tank
One of the first things to check when your car doesn’t start, whether the engine turns over or not, is the fuel tank.
Many people forget that they don’t have any fuel in the fuel tank, or the fuel gauge is not reading the correct fuel amount, indicating you have some fuel.
Check the computer sensors (modern cars only)
Modern vehicles are equipped with additional sensors for better performance, including the crankshaft position control sensor, the camshaft position sensor, the throttle position sensor.
A problem with one of these sensors can prevent your vehicle from starting. Thus, troubleshoot any codes in your vehicle’s internal computer. Some of these codes might be pending and will trigger a check light very soon.
Refer to your vehicle’s owner’s manual to locate these sensors and to understand how to troubleshoot them and make sure they are in good shape.
Check your battery
The most common cause for your engine to turn over but not start is a faulty battery. Your car’s battery can go bad for different reasons, including:
- the battery passed its lifespan
- the battery was exposed to extremely low or high temperatures
- the battery has corroded or rusted cables
- the battery has loose cables
the best way to confirm its the car battery causing the problem is by jump-starting your car. If the jump-start works, the battery is the culprit. If the jump-start did not help, other components are the culprit
Battery replacement price ranges from $50 to $120 on parts only.
Check your car’s starting system
Any problem with the starting system can easily prevent your car from starting, even if your engine has a little power to turn over.
To further investigate the problem, check the voltage drop in the circuit and look for weird clicking noises.
Check issues with the car’s security system (modern cars only)
For added security, newer vehicles might be equipped with certain security systems preventing the vehicle from igniting or starting.
A small issue with your key chip can throw a wrench in your day and disturb your trips.
Problems with security issues are usually more complicated, and there is nothing you can do other than consulting the dealership or a professional mechanic to resolve it.
Check your fuse box
The last quick check you can do is a blown or damaged fuse. Refer to your vehicle’s owner’s manual and locate your car’s fuse box.
In the fuse box, look for signs of burnt or damaged fuse wires as any such sign indicates a blown a fuse, which is a very common cause of car not starting while the engine is turning over.
If you don’t have basic mechanical skills, it's better to have your car inspected and repaired by a professional mechanic.
On the other hand, if you are comfortable enough to do additional troubleshooting, you need to check if your engine has the required items to operate efficiently. Your engine needs spark, fuel, and strong combustion.
Below are several items to troubleshoot and pinpoint the culprit:
Does your engine has the required spark?
Without a spark, the cylinders will not burn the fuel and get your vehicle moving. Even if you have some power in the engine, it might not have the continuously required spark.
To troubleshoot your engine’s spark, you need to follow these steps:
- Prepare the required tools
- You will need an adjustable spark tester to test for 40KV, 30KV, and 10KV
- Your vehicle’s owner’s manual to locate the spark. If you don’t have a copy of your vehicle’s owner’s manual, you can download a soft copy from the internet or request a hard copy from your mechanic
- You need a friend to assist you to crank the engine while you watch the spark tester response
- Following the instructions in your vehicle’s owner’s manual, locate the spark and unplug it. Try to work with a spark plug that’s easy to reach. Your spark plug comes in three forms: a plug wire, a coil on plug, or a coil wire spark.
- Please adjust the spark tester to test for a 40KV and connect it to the spark and the engine ground.
- Have your fried cranks the engine while you monitor the response of the spark tester.
- If your car’s spark is in good shape, you will see a bright spark in the spark tester as your engine cranks.
- If you did not see a spark with the 40KV spark tester, repeat the test using a 30KV and 10KV tests.
- If you still can't see a spark, the problem has to do with the ignition. It would help if you had a professional mechanic inspect the ignition coil, module, igniter, or ignition distributor.
Does your engine receive fuel?
If you confirmed that your engine has a good spark, the problem could be your engine cylinders are not receiving any fuel due to a clog somewhere.
Thus, you must inspect your car’s throttle body injection system following these steps:
- Under the air filter box lid, locate the carburetor right on top of the throttle body injections system. If you have trouble locating the carburetor, always refer to the vehicle’s owner’s manual.
- Have your friend crank the engine again and watch if the fuel is supplied to the cylinders.
- If you don’t see any fuel fed to the unit, the problem has to do with your fuel delivery system. Here is some housekeeping to keep in mind:
- As we mentioned earlier, make sure that your fuel tank has enough fuel
- Make sure the fuel pump doesn’t have any problem
- Confirm that the fuel filter is not clogged with dirt, especially as you run your car on low fuel, or when using fuel with low quality
- Finally, make sure the fuel injectors are also not clogged, and the fuel is running smoothly through them.
Does your engine have the required compression?
Assuming that your engine has a good spark and the fuel is fed to the units properly, the next thing you can do is to ensure there is enough compression in the combustion chambers.
In your engine’s cylinders, the air-fuel mixture receives a spark to create the required explosion. If there is an air leak in these cylinders, the explosion will not be strong enough to generate the necessary power needed to move your vehicle.
There are common air leak locations to the combustion chambers, including air escaping through a jumped timing chain valve.
Furthermore, air can make its way to the combustion chamber due to a worn-out ring, blown head gasket, or a burned valve.
To confirm that your engine has compression issues, you can visually inspect the timing belt and look for worn-out or damage signs. Usually, the timing belts need to be replaced once every five years.
As the timing belt goes bad, it will not synchronize the camshaft to the rotation of the crankshaft. Thus, your engine will not have the required compression.
You can also use a compression gauge to check the compression pressure in your combustion chamber. Usually, any gasoline engine must pressure between 130 and 180 psi, where diesel engines must have a pressure between 250 and 400.
I followed all the steps and still can’t identify the culprit, are there any other recommendations?
Well, if you followed all the steps and were not able to identify the problem yet, here are other things to check and keep in mind:
Are there any issues with the Exhaust Gas Recirculation Valve (EGR)?
Your engine has an exhaust gas recirculation valve to reduce the engine’s temperature and harmful emissions (EGR). This valve controls how much air-fuel mixture enters the intake manifold in preparation for returning.
A simple problem with the EGR valve can prevent your engine from starting even after turning over for a little bit. The valve can usually stick open or closed, disturbing the engine’s overall function.
How about the cold injector (not all cars has it)?
Some cars are equipped with cold injector. This injector works only when the engine is at low temperature before it heats up. A bad cold injector can prevent your engine from starting.
Since not all cars have cold injectors, the best place to confirm whether your car has it if your vehicle’s owner’s manual.
Did you check the mass airflow sensor (MAF)?
For your engine to produce the power, it must receive a certain amount of air in addition to the fuel. The mass airflow sensor is responsible for monitoring how much air is entering the combustion chamber.
It is not rare for the MAF sensor to get blocked or clogged by dirt or any other foreign objects causing the engine not to start.
Look into the engine coolant temperature sensor (ECT)?
Your engine operates only within a certain range of temperature, as stated in your vehicle’s owner’s manual.
Using the engine coolant temperature sensor's support, your vehicle’s computer regulates the amount of fuel fed to the engine along with the perfect timing for the coolant fan to start.
Sometimes problems with the engine coolant temperature sensor can prevent your vehicle from starting.
Did you check the canister vent valve?
As part of your vehicle’s emission control system, not all harmful emissions are released to the atmosphere to prevent the environment. Instead, these harmful gases are stored in a specific canister and routed back to the intake manifold for reuse in the combustion chambers.
The flow of these harmful gases is controlled by the canister vent valve as it receives a signal from your car’s internal computer when the time allows.
A small problem with the canister vent valve can also affect your engine starting process if not prevent it.
If your engine turns but won’t start, the problem can either be related to the battery, battery cables, ignition switch, starter, or fuel filter. If none of these components have an issue, you need to check your engine’s spark, fuel supply, and compression.
This article provided you with detailed guidance on which components to check to identify the root problem of your engine turning over but not starting.
Despite the cause of the problem, you must get it resolved as soon as possible to avoid dealing with more complicated issues.
While some of these repairs are a little pricy, most engine starting problems are not very expensive when it comes to parts. However, labor cost can be a little pricy, especially if you had the job done at a dealership instead of a small repair shop.