It is never a pleasant experience if the car shuts off while driving, and I can only imagine how scary it must be if it happens to you on a highway or leaving you stranded in the middle of nowhere. Luckily, it only happened to me right outside my house.
However, this issue is often due to a lack of maintenance, and many people don’t have the knowledge or care enough to take care of their cars the way they should.
In a survey by Utires, over 91.8% of car owners admitted they have at some point delayed repairs or services due to no time or even anxiety. Which increases the risk of more things breaking.
This article will list the most common reasons why your car shuts off while driving and give you the basics on how to diagnose the cause.
Most Common Reasons A Car Shuts Off While Driving
The most common reason a car shuts off while driving is because of a bad crankshaft position sensor or fuel pump. If there is no electric power and the car won’t start, it’s likely caused by a bad alternator. However, it can also happen due to a bad ignition switch, an empty fuel tank, or engine sensor problems.
1. Bad Crankshaft Position Sensor
The crankshaft position sensor is responsible for sending information about the crankshaft’s position to the car’s computer and is necessary for the engine to run on most car models. If it goes bad or sends the wrong information to the car’s computer, the engine may shut off.
However, some car models have a camshaft position sensor which the car uses instead if the crankshaft position sensor is faulty, which means it may not cause the car to shut off entirely.
2. Bad Fuel Pump or Fuel System
A fuel pump provides the engine with the correct amount of fuel to run. If your car has a problem with the fuel pump, it will not be able to supply it with the correct amount of fuel, and the car will eventually shut off.
Most fuel pumps are located inside the fuel tank, and a common sign of an old or worn fuel pump is a noticeable loud whine or howl from the tank while running.
Mechanic tip: When your car shuts off, give a small kick to the fuel tank with your foot or similar and then see if the car starts. If it does, it is a big chance you have a problem with your fuel pump.
However, there is no bypass for a faulty fuel pump. To get your car working properly again, you will have to fix or replace the fuel pump.
Apart from the fuel pump, other parts of your car’s fuel system can cause this problem as well. A clogged or restricted fuel filter will also prevent enough fuel from reaching the engine. Fortunately, it is relatively easy to replace a fuel filter.
If you noticed your car was sputtering or jerking before completely shutting off, or your car turns off while driving but turns back on – you may be dealing with an issue due to a bad fuel pump or fuel system.
3. Empty Fuel Tank
It might feel like an obvious thing everyone knows about, but if your car has an empty fuel tank, it will eventually run out of gas and shut off. And, you would be surprised if you knew how many people are getting stranded because of this.
However, if your fuel gauge or fuel level sender is broken, it might give you a false reading and make you think there’s still gasoline when there isn’t.
If you think you are having a problem with your fuel gauge or level sensor, you could try to fill 1 gallon (about 4 liters) of fuel in the tank to see if it starts.
4. Bad Ignition Switch
Your car’s ignition switch is essential for keeping your vehicle running. It is located behind the ignition lock, where you put your key or press the button to start the car.
Inside the switch, tiny metal plates connect each other, essential for the ignition switch to work. However, due to corrosion and rust, these plates may lose connection causing the ignition to switch off when it shouldn’t.
And as a result, it will cause the engine to shut down immediately and could be why your car shuts off while driving. Luckily, this is easy to diagnose and there are a few common symptoms of a bad ignition switch to look for.
If all the dashboard lights flicker or die together with the engine, it is a big chance your ignition switch is faulty or failing.
5. Alternator Issues
While driving, the alternator supplies electricity to vital components of your car, including sensors, ECU, fuel injectors, and your accessories such as the radio, dash, air conditioning, etc.
It is also constantly charging the battery. Without it, your battery would drain fairly quickly. So if your alternator fails, either the alternator itself or the serpentine belt driving it breaks, then your battery will quickly drain. Eventually, the car will shut off while driving.
If the serpentine belt breaks, you will likely notice a loss of power steering or the car overheating before the engine turns off because of the drained car battery. If you do notice this, immediately pull your car to the side of the road and turn off your car.
When an alternator is going bad, most times the car battery light comes on. It indicates that your car is having battery charging problems. But, before blindly spending money on an alternator replacement, it’s a good idea to get it tested.
However, if you try to start your car after it shuts off while driving and it still has electrical power and the starter motor works, your alternator is fine.
6. Dead Car Battery
Although it is rare, a bad or dead car battery can cause a car to shut off while driving. The alternator should give the power needed for your car’s electrical components and accessories, but in some rare cases, a short circuit in the car battery can cause the engine to shut off.
Keep in mind that signs of a bad car battery vs alternator is often similar, we therefore recommended to get both tested before replacing any part.
7. Malfunctioning Sensors
Today, modern cars have a lot of sensors. They are responsible for various car functions such as fuel mixture, airflow, exhaust gas composition, and more.
Most of your car’s sensors won’t cause the engine to shut off. Although, if sensors like MAF sensors, engine coolant temp sensors, or oxygen sensors fail or give incorrect readings, it can cause the engine to shut off.
Mass Airflow (MAF) Sensors: Failing mass airflow sensors is a common cause of car engines shutting off. The MAF sensor measures the air flowing into the engine and sends this information to the car computer.
If it’s not working correctly, the car will run lean (too little fuel) or rich (too much fuel). This can cause the vehicle to stall and the engine to die.
Engine Coolant Temp (ECT) Sensors: These sensors monitor the temperature of the coolant and send this information to the car computer. If the temp sensor sends the wrong information, the computer might reduce the amount of fuel going into the engine, causing the car to stall.
If it’s not working, the car computer won’t be able to adjust the fuel mixture correctly and could cause the engine to shut off.
A sign of a faulty sensor is a check engine light illuminated on your car’s dashboard.
How to Troubleshoot a Car That Shuts Off While Driving
If your problem with the car shutting off while driving occurs occasionally, it is harder to diagnose the reason.
However, if your car just died and won’t start again, you can try a few steps to troubleshoot the issue, some of which are easier than the others.
Check For Empty Fuel Tank: An easy way to check if something is wrong with your fuel gauge or level sensor is to fill your tank with 1 gallon (4 liters) of fuel. If your car then starts, you found the problem.
Check for Trouble Codes: Use an OBD2 scanner to check for trouble codes in the engine control unit (ECU). If you get any, continue the diagnostics of the trouble code appearing.
Charge Your Battery: Make sure your car battery charge is good by connecting a car battery charger. You can also check the battery voltage. If it’s between 12.2 and 12.8 volts, your car battery is in good condition to start the car.
Check the Alternator: If the car starts after charging the battery, it indicates that your alternator might be bad. Keep your car running and measure the voltage on the car battery with a multimeter.
A voltage reading between 13.5 and 14.5 means your alternator is fine. If it’s under 13 volts while the car is running, something is wrong with either the alternator or the belt driving it.
Check Fuel Pressure: An easy way to see if the fuel pump and fuel filter are working properly is to use a fuel pressure gauge to determine if the engine has the correct fuel pressure. If not, replace the faulty pump or filter.
Check the Crankshaft Position Sensor: Keep your eyes on the RPM meter while cranking the engine. If the RPM doesn’t move, it’s a big chance you have a problem with the crankshaft position sensor.
What to Do If the Car Shuts Off While Driving
Here is what to do if your car randomly shuts off and leaves you stranded in the middle of the road.
Try to Restart Your Car: The first thing you should do is to try to restart your car immediately. If your car restarts, drive home or to the nearest auto repair shop and find out why your car stopped so it doesn’t happen again.
If it doesn’t start, go to the next step.
Use Emergency Lights & Triangle: If you cannot restart your vehicle, it is necessary to put on emergency lights to notify other drivers. If you have a roadside emergency kit, make sure you can leave your vehicle safely and set up the triangle 50 to 100 meters behind the car to warn other drivers that a vehicle has stopped on the road.
Take Your Car to the Side: If possible, and if it’s safe, try to push or get the car to the side to prevent accidents. Hopefully, someone will stop to help you.
Call for Help: If you can’t restart your car, you will need to call for help. You can call a tow truck, friend, or family member.
Why Do My Car Turns Off While Driving But Turns Back on?
The most common reason a car turns off while driving but turns back on is due to a bad fuel pump. The engine needs a certain amount of fuel at a precise moment for the combustion to generate power. The fuel pump is a vital part of this process, supplying the engine with the correct amount of fuel.
Why Do My Car Shuts Off When Stopped or Slowing Down?
The most common reason a car shuts off when stopped or slowing down is due to a malfunctioning automatic transmission. With a low fluid level or a broken torque converter, the car will not be able to maintain power at low speeds, causing the engine to shut off. A bad fuel injector or pump can also cause this to happen.
Why Did my Car Shut Off While Driving And Won’t Start?
The reason a car shuts off while driving and won’t start is likely due to a bad alternator or low fuel pressure. If your alternator has failed, you will have a drained car battery, and you will notice the starter motor not working. If you think it is the fuel pressure, you should check the fuel pressure with a fuel gauge.