Automotive Maintenance And Detailing


Automotive Maintenance And Detailing

What is the starter motor of a car?


What is the starter motor of a car? The starter motor is an essential device for starting a car engine. If this part doesn’t work, you may not be able to start the engine without someone helping to start the car.


The starter motor is mounted on the flywheel gear tooth. You can find it where the gearbox is connected to the engine. The starter motor is activated when you turn the car key or press the start button.


The car engine is started by a spin of the crank, which draws air from the intake vents and generates compression over the cylinder.  Then causes the combustion chamber to ignite with spark plugs and fuel injectors in both gasoline and diesel engines. The starter motor stops as soon as the engine starts.


For the starter motor to work, you need a battery with sufficient current. You may not be able to start the car if the battery is weak. Therefore, your failure to start the engine may not be the sole cause of a broken starter motor.


There are several solutions to fix the problem when the starter motor fails, from workaround to replacing the motor. Each solution has a different cost.

How does the starter motor works ?.

The starter motor is a small but powerful electric motor.  It uses 12 volts of the battery to spin.  There are the internal components have two important parts: the motor winding assembly and the electric solenoid. The motor windings generate a magnetic field to move the motor axis with gear teeth to the flywheel. The electric solenoid is responsible for pulling and pushing the motor axis through the Bendix gear to allow the gear to grind the flywheel gear. That also makes connecting the electrodes to keep the motor running. All operation of the starter motor takes place when you turn the car key or press the engine start button.

The engine start-up from the starter motor doesn’t just happen because you turn the car key. It has other conditions for the safety of use. As you turn the starting key, the car’s computer system checks the gear and clutch position sensors. In an automatic transmission car, you need to make sure that the P or N gear is on.

On manual transmission cars, you have to keep the clutch pedal pressed. The sensor signals to the computer that the clutch disc has already been cut from the flywheel.

Then the current from the key or start button is passed through the relay to the solenoid installed in the starter motor. The electric current enters the solenoid causes the magnet to push the gears of the starter motor axis into the flywheel gear.   Concurrently, the solenoid pushes the bridge to connect the electric current to the motor, generating an electromagnetic, and causing the starter motor’s armature to spin. The motor rotates the flywheel while the ECU signals the fuel pump to run with the ignition coil generates high voltage to the spark plugs. The engine should then start as soon as the starter motor spins.

When the engine starts, the starter motor will stop immediately. The solenoid will pull the motor gear from the flywheel and disconnect the electric current to the motor.

A motor starter is mounted on the engine flywheel

What are the symptoms of a malfunctioning motor starter?

If you can’t start the engine, there are important reasons to check the starting system. Battery power system, starter motor, gear, or clutch position sensor


Symptoms that you may experience when it doesn’t start up might be this.

 – There is no sound of the starter motor when turning the ignition key.

 – The sound of the starter motor spins but turns slowly


You or the mechanic will need to figure out if your car has this kind of fault to make sure it has a problem with the electrical system or has starter parts or sensors broken.

How to check

  1. Check the battery

The batteries that have been used for a long time may not have sufficient current (amps) to the starter motor’s rotation. Each car model has a battery amp setting, which you may find in your owner’s manual. Diesel cars tend to have a higher battery amp than petrol or mid to small passenger cars.

The CCA or Cold Cranking Amps of the battery must be within the standard value.  Dropping in CCA will prevent your car from starting, and you need to replace the battery. You can learn more in this Car Battery article.

Warning: Using a voltmeter to measure the battery voltage may not be able to tell if the battery is dead. You may be able to measure at 12 volts, which is probably their standard battery voltage.  However, in reality, you need to focus on the amps or CCA mentioned above.

  1. Check the terminals for the battery and starter motor.

There are cases when the car cannot start because the battery terminals or starter motor are dirty. If you are sure that the battery is not damaged, you should check the wires in the following locations.

  1. Battery terminals. Check the positive and negative terminals of the wires by removing them. Clean the electrodes by pouring hot water or sandpaper. Reconnect the terminal and tighten the nut.
  1. Wiring terminals of the starter motor. The starter motor uses a high current to run the motor, so it has a big red wire coming directly from the battery. It can be easily noticed. Remove the positive terminal on the starter motor and clean it with sandpaper. Do the same with the negative terminal connected from the starter motor to the ground on the engine or car body frame.

Besides, you or the technician should check the relay switch of the starting system.  To see if it broke or not. You can check the installation location of the relay from the owner’s manual.  A breakdown of the starter relay leaves no current to the solenoid in the starter motor.   It prevents the engine from turning on.

3.Check the gear or clutch position sensor.

In an automatic transmission car, you will not able to start the engine if the D or R position is engaged. You must always keep gear in P or N position to start the engine. That is because the car manufacturer doesn’t want you to be in an accident if the car can move forward while the engine starts.

The same in a manual transmission car, you must always press the clutch or shift the gear to the neutral gear before starting. The engine may not start if you keep the gear engaged and do not press the clutch while starting.

You can check the operation of the gear position sensor by moving the gear selector to N and then starting the engine.   If it starts on the N but not in the P or vice versa you have some problems with the gear position sensor.

The technician will have a way to check these sensors with specific tools. You should have a technician analyze and fix it.

Should we repair or replace the starter motor?

The motor starter can be repaired

If the starter motor is damaged by its internal components malfunction, you have two options: repair it or replace it. The choice you decide may depend on the budget you have.


Replacing it, of course, costs more money than repairs. However expensive or cheaper, depending on your car model. Small to medium-sized passenger cars tend to be cheaper than expensive cars.


We can not show the certain cost of the new starter motor because it depends on what is your car model, engine type, and brand. You may need to pay between $ 200 and $ 400 per motor. The repair cost depends on the difficulty of removing and replacing parts, and also the area you live in.  We advise you to check the repair price with the nearest garage.


You will spend less money on repairs.  Most of the starter motors are broken because the damaged carbon brushes which conduct the electric current of the motor core wear out. A technician can replace it for a few dollars, excluding labor. You may end up spending more time but paying less.

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