You should follow the optimal routine when using your vehicle. It's important to be aware of what you are doing, especially if your driving experience is not that rich yet. A lot of questions I get in my social media and in the comments under some articles are about cases when the driver accidentally turns the ignition when the engine is running.
If you crank the engine when it's already running, it may be quite bad for the machine if the car is old and has simple electronics without fool-proof technologies. But in the majority of modern vehicles, this will be just OK because the electronics won't allow you to actually crank the engine and do some harm to the gears.
But in this article, I want to tell you more about some of the possible consequences.
How can you potentially crank the engine when it is running?
Cranking the engine when it's running is possible when you turn the key to the "crank" position accidentally when the engine is on. It means your starter will get the signal from the ignition cylinder and the engine may crank if it's not protected by a special setting in the ECU.
This may happen when you are panicking or when you just haven't yet learned your car well enough to avoid such issues.
For an experienced driver, it may seem pretty comic but this problem is not as uncommon as you may think.
Fortunately, if you have a push-button start in your vehicle, it should be impossible to activate the starter motor when the engine is running. By pressing the button when the car is on, you will turn it off. Or, if your vehicle is moving, nothing will happen as the button won't turn off the car when it's on the road.
But for the old-fashioned key ignition cylinder, everything is possible, so you will need to be careful.
Will the starter motor be dead after such an event?
Well, as I've already told you before, on the majority of modern vehicles, nothing will happen if you accidentally move the key to the cranking position when the engine is already running. Your ECU will make sure that the starter motor isn't activated and you can be sure that it's not damaged.
But if you have an older or cheaper car with not as much automation in it, it can activate the starter motor even if the engine is running.
Here's what happens then:
- your starter motor tries to crank the engine;
- for this, the starter solenoid will push the starter motor gear (bendix) towards the engine;
- but the gear on the flywheel is already rotating pretty fast, especially if you drive and the engine is not just idling but revving up;
- so, the gear on the flywheel which is made of more durable metal, will basically destroy the starter motor gear;
- the best possible situation is that you will need to replace the starter gear as it will have several teeth off;
- the worst-case scenario is a dead starter motor and also damaged flywheel gear.
Unfortunately, if the starter is broken, it will need replacement. But if only the starter motor gear is affected, it can be replaced without buying the new starter motor. The worst thing that can happen is the gear on your flywheel may lose several teeth. This will require expensive and labor-intensive repairs as the transmission will have to be removed to change that gear.
Anyway, the parts won't cost you a fortune. But I don't recommend DIY repairs. You will need to have your vehicle properly inspected before you keep driving it.
What are the symptoms of the damage?
So, if you turned the key to the cranking position when the engine was running and heard some weird sound, you may be sure that something bad happened.
Here are the symptoms you should remember:
- when you turned the key to the crank position, you heard some noise immediately (grinding, for example);
- after you turned off the vehicle and tried to start it again, it didn't sound as it had before;
- you sometimes can't start the engine - the starter motor seems to be rotating without cranking the engine;
- after the engine is started, you hear some weird noise for several seconds.
If this is happening with your car, it's time for you to take your car in for an inspection. DIY inspection is also possible sometimes. If you have the skills to take off the starter motor, you can inspect its gear. But to check the flywheel gear, you will anyway need to take the vehicle in.
About the authors
The CarAraC research team is composed of seasoned auto mechanics and automotive industry professionals, including individuals with advanced degrees and certifications in their field. Our team members boast prestigious credentials, reflecting their extensive knowledge and skills. These qualifications include: IMI: Institute of the Motor Industry, ASE-Certified Master Automobile Technicians; Coventry University, Graduate of MA in Automotive Journalism; Politecnico di Torino, Italy, MS Automotive Engineering; Ss. Cyril and Methodius University in Skopje, Mechanical University in Skopje; TOC Automotive College; DHA Suffa University, Department of Mechanical Engineering
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