How Do Starters Work in the Car?

Ever wondered how your vehicle’s engine cranks? When you turn the key in the car ignition, there is so much going on in the engine. The starter motor is the key component in an internal combustion engine. It is powered electrically and plays a significant role in starting the engine. The starter provides an initial turn to the engine, after which it continues rotating on its own.

Read the complete guide to learn about the working of the starter and how each of its parts contributes to the whole operation.

Components of starters and their functions

1. Armature

The armature is an electromagnet mounted on the armature shaft. This component is made up of a laminated soft iron core wrapped with conductor windings. The armature and commutator share an axle, which supplies current to create an electromagnetic field.

2. Commutator

The commutator is present at the rear of stater housing. It consists of two plates that are attached to the axle. These plates serve as two connections for the windings of the electromagnet.

3. Brushes

There are carbon brushes attached to each commutator plate. These brushes rub the commutator, conduct electricity, and provide it to armature coils.

4. Solenoid

The starter’s solenoid has a movable plunger wrapped with two coils of wire. The weaker coil holds the plunger in position while the stronger one draws in it. It acts as an electric relay to connect the starter motor to the vehicle’s battery. Furthermore, it has two terminals, the input terminal for the positive battery cable and the output terminal for the cable that supplies current to the starter motor.

5. Plunger

The plunger works with the solenoid. It moves forward to engage the pinion with the flywheel ring gear.

6. Lever Fork

The lever fork is connected to one end of the plunger. So, when the plunger moves forward, the lever fork moves with it, and this activates the pinion.

7. Pinion Gear

Sometimes they are also known as starter gear or drive gear. The pinion gear is connected to the armature shaft through overrunning sprag clutch. The clutch enables the pinion to transmit the drive in one direction only. After providing initial turn, pinion disengages with the flywheel to prevent any damage to the starter motor.

8. Field Coils

Field coils catch power from the battery, which transforms them into an electromagnet. This generates a magnetic field around the armature. Field coils consist of two to four coils connected in series and held by screws in the housing.

Working of starter

Starter acts as an electric motor, and it works when you turn the key in the car ignition. It turns over the engine, making it suck in the air. Air is important to begin the fuel combustion; without it, the engine will not start. This flow of air inside the engine can only be achieved by creating suction, and it happens when the engine turns over. 

The car’s engine consists of a flexplate or flywheel, which has ring gear around the edge. Also, the starter pinion gear is designed to fit temporarily into the grooves of the flywheel ring gear, and this connection is responsible for rotating the engine.

The starter motor has two circuits; the starter and control circuits. The starter circuit takes the currents from the battery to activate the starter motor, but it does not activate immediately. The battery activates the control circuit first, which energizes the solenoid. 

Once it is energized, the solenoid draws the plunger down, which completes the starter circuit and large current flow to the starter motor from the battery. At the same time, the plunger interacts with the lever fork to push the pinion gear forward to fit with the flywheel ring gear. Finally, the current flowing to the starter motor power it up then rotates the flywheel.

As the engine turns over, the electromagnet stops and disengages the starter. Simultaneously, pinion gear detaches from the flywheel to prevent any damage. This is essential because the backdrive from the flywheel can damage the starter and pinion gear.