In these modern times, starting the car is just one button away but sometimes things do not go as planned and the car turns over but won’t start.
When the engine cranks but the car won’t start, the underlying problem might be everything from bad spark plugs to bad compression ratio.
In the following article, the most common causes will be discussed so you can quickly resolve and fix the problem as soon as possible.
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Why Is My Car Cranking But Not Starting?
The ignition system is responsible for starting your engine. Even though it takes only a second or two for the engine to start, the ignition system consists of many components that work together.
When you turn your key or press the start button to start your car, the starter, which is electrically powered, turns the engine and the cranking sound is heard.
The characteristic sound you hear when starting your car is the crankshaft and pistons moving, creating a beginning of the engine cycle.
If the car cranks but won’t start, the problem is in one of the components of the chain reaction described above.
Usually, when you hear the car continuously cranking, the starter motor is not the culprit, but another part is. The most common causes are related to the following components:
- Fuel flow
- Spark plugs
- Compression ratio
Down below, you will find out how to test all these potential culprits and how to fix them.
Bad Fuel Flow
In order for the engine to start and work properly, fuel has to be delivered to the combustion chamber. If proper fuel flow is not achieved, the engine will not start.
The three main causes of bad fuel flow are problems with the fuel pump, fuel injector, or simply an empty fuel tank.
Bad Fuel Pump
The fuel pump is responsible for pumping the fuel from the fuel tank to the fuel injector. If it turns out that the fuel pump is the culprit there is a simple way to test it.
As you turn on the ignition (without turning on the engine) you can hear the fuel pump activate and emit a small buzzing sound.
In some cars, the fuel pump engages at the same time when the engine cranks making it much harder to hear the fuel pump. If you do notice the fuel pump activating, it is a good sign, but more testing may be needed.
Bad Fuel Injector
As the fuel pump delivers the fuel, the fuel injector is responsible to forward it to the combustion chamber. If your car uses a throttle body fuel injector, you can visually inspect the spray
If your car uses an electronic fuel injector, the best way to make sure if it works properly is by listening to it. To do so you can either use a cheap mechanic’s stethoscope or use a simple screwdriver.
Using a stethoscope or a screwdriver, put the tool on the body of the injector and listen for a clicking sound. The sound you hopefully hear is the valve opening and closing.
Empty Fuel Tank
If there is no fuel available, logically, the engine will not start no matter how hard you try. If this is the case, the solution for the problem is the easiest one on this list.
Make sure that no leaks caused the empty fuel tank and that all the fuel lines are intact.
Bad Spark Plugs
Spark plugs ignite the fuel-air mixture in the combustion chamber. If the fuel-air mix does not combust, the engine will not work.
Bad spark plugs usually affect your engine noticeably when driving as the engine is prone to misfiring, rough idle, hard to accelerate, and so on.
If you noticed these symptoms before your problems with starting the car occurred, the spark plugs might be the problem.
A spark plug tester can help you diagnose the problem, however, in a lot of cases, bad spark plugs can be visually diagnosed. Also, make sure that the ignition coils are not the culprit in this case.
The crankshaft plays a pivotal role in the synchronous events that occur when the engine is running.
If the crankshaft is the culprit in this scenario, it is most probably due to a faulty crankshaft position sensor.
The position sensor sends information to the ECU which in turn enables the spark plugs to fire at exactly the right time.
A faulty sensor would therefore lead to ineffective combustion that would lead to an inadequate amount of power generation to keep the engine running (or starting).
Insufficient Compression Ratio
A compression ratio that is not adequate for combustion of the air and fuel mixture will result in a similar result as a faulty crankshaft sensor described above.
In this case, the lack of compression is most likely due to leakage caused by bad seals and gaskets. It could also be a problem with a malfunctioning timing belt.
To solve this problem, new piston rings, valve seals, or anything else that hinder an adequate compression ratio to be achieved, should be replaced.
As mentioned before, the starter plays a vital role in starting the engine and it is electrically powered. Because the engine does not work, all the electricity comes from the battery and not the alternator.
A faulty starter usually presents with a grinding noise, if you do hear this you should stop trying to turn on your car as you could inflict serious damage the flywheel.
If the battery or starter is bad, the starter may not get enough power to start the engine. Also, a lot of other components are electrically powered, such as the fuel pump.
A bad battery would not be able to power all the different components at once, making it impossible to start the car.
Another possibility for a faulty power supply may be a problem with a blown fuse. To test the fuses, simply turn the ignition on and see with a test light if electricity if there is any current.
If the engine cranks but car won’t start, then something is wrong with the ignition system. The system consists of multiple components, and all may have a role in an unsuccessful start.
Unless the car does not produce a nasty grinding noise, the starter is probably not the culprit.
In most cases, the components at fault are usually related to fuel flow, spark plugs, the crankshaft, compression ratio, and the power supply.
All these things can be tested, some are easier than others to test, and some need a good amount of experience to notice where the fault is.
Make sure to keep track of when different components were replaced, as often, the faulty component is usually overdue for its planned lifetime.
It is therefore important to service your car regularly and change each component at intervals determined by your car manufacturer.