How does Starter Motor work? | Signs of bad Starter

The starter is one of the most important parts of the car. The starter is also known as a starter motor, cracking motor, or self-starter. It uses to initially turn the crankshaft of the engine. As the engine starts, the starter motor disconnects. As the starter goes bad, the engine doesn’t start or it takes too long time. This article explains the working, types, and symptoms of a bad starter motor.

What is Starter Motor?

A starter motor is a mechanical device used to turn the crankshaft of the IC engine so as to start the initial operation of the engine under its power. These are electrically, pneumatically, or hydraulically operated motors.

Starter Motor

The main function of the starter motor is to initially turn the engine crankshaft and start the engine. When the engine starts to run, the starter disconnects from the engine; after that engine depends on the power produced by the air-fuel mixture combustion process.  

The electric starter contains a powerful solenoid and a Direct Current (DC) motor. The solenoid is directly connected to the battery of the car. It gets hearth current power from the engine body while the positive current comes directly from the battery.

The vehicle must have a 12-volt battery to start the motor. In simple words, your vehicle battery must have adequate power to run the motor. In some cases, the starter clicks, but it doesn’t start; the problem is with the battery or the starter motor itself.

The main function of the starters is to initially turn the engine crankshaft one or two times required to start the engine.

Working Principle of Starter

The working of the starter is very simple and easy to understand. It contains four field windings installed inside the housing. The armature is linked to the field coils via carbon. The starter motor gets power from the vehicle battery.

Starter Motor

As you press the ignition key, the battery activates and transfers power to the solenoid.

The solenoid further transfers power to the starter motor. When the starter motor gets power, it pushes the pinion gears forward to mesh with the engine flywheel. The flywheel is connected to the crankshaft of the engine.

As the motor turns, the flywheel also turns, which further turns the crankshaft of the engine. When the crankshaft turns, the engine starts, and the combustion process of the air-fuel mixture starts. As the combustion process starts, the motor stops, and the engine further gets power through the combustion of the air-fuel mixture.

Parts of Starter

The starter motor has the following parts:

  1. Armature
  2. Commutator
  3. Brushes
  4. Solenoid
  5. Plunger
  6. Lever Fork
  7. Field Coils
  8. Pinion

1) Armature

The armature is one of the parts of the starter. It is installed on the bearing or driveshaft for a guide. The armature consists of a laminated soft iron core. Multiple conductor windings or loops use to cover this core.

2) Commutator

It is an electrical switch that periodically reverses the current between the external circuit and the motor. The commutator consists of two plates attached to an armature shaft. These plates ensure proper connection for the coils of the electromagnet.

3) Brushes

The brush is the part that runs in the commutator section on the back of the case. It shines the commutator to conduct electricity.

4) Solenoid

The solenoid or electromagnet has two coils wound around an iron core. It acts as a switch to start and stop the electricity flow between the car battery and the starter motor.

5) Piston or Plunger

It is installed at the end of the pinion. As it moves forward, it engages the pinion.

6) Lever Fork

It connects to the plunger. It moves forward along with the plunger to engage the pinion.

7) Field Coils

The field coils install inside the casing of the starter motor. The motor has two or more coils connected in series. As the coils get electricity by the battery, they convert it into an electromagnet and rotate the armature. When the armature rotates, the magnetic field is produced around the armature.

8) Pinion

It contains springs and gears. As the motor starts, the pinion immediately engages and starts the engine.

Types of Starter Motor

The starter motors have the following types:

  • Direct Drive (DD) Starter Motor
  • Planetary Gear Reduction (PLGR)
  • Permanent Magnet Gear Reduction (PMGR)
  • Permanent Magnet Direct Drive (PMDD)
  • Off-Set Gear Reduction (OSGR)
  • Inertial Starter

1) Direct Drive Starter Motor 

It is one of the most famous and oldest types of starter in the market. The working of the direct drive is simple as other types. It is a solenoid-operated device. There are multiple designs of direct drive starters available in the market.  

The solenoid is directly connected to the vehicle battery. As you press the ignition switch, the solenoid receives power from the vehicle battery.

As the solenoid gets power, it pushes the plunger and moves the lever that guides the pinion. This pinion then engages with the flywheel of the engine. So, when the starter turns, the flywheel also spins, which starts the combustion process in the engine combustion chamber.  

2) Planetary Gear Reduction (PLGR)

The existence of this type of starter has largely replaced the direct-drive starters. This type is a permanent magnet that transfers power between the armature and the pinion shaft. The armature of this gear rotates faster.

The planetary gear starter motor contains three plenary carrier gears and one sun gear. The sun gear installs at the armature end while the plenary gears install within ring gear held stationery.

3) Permanent Magnet Gear Reduction (PMGR)

These types of starters have low heat build-up, lightweight, easy to install and construct. The permanent magnet gear reduction PMGR has 4 to 6 magnet field packs.

The 12V solenoid of the starter has three terminals and heavy-duty construction to reduce the current requirement. This type doesn’t contain a field coil. Therefore, the brush and commutator transmit power directly to the armature.

4) Permanent Magnet Direct Drive (PMDD)

It is similar in some respects to direct drive. The difference between the PMDD and the direct drive is that the PMDD uses a permanent magnet instead of the field coils.

5) Off-Set Gear Reduction (OSGR)

These types of starter motors operate at low currents and high speeds. Off-set gear reduction starters have a lightweight, easy assembly, and compact design. They are most commonly used on 4WD vehicles because they increase starting torque.

6) Inertial Starter

They are electric types that have the ability to gain the characteristics of all other starter motors. They work efficiently on startup and also protect the motor parts. They start the engine powerfully and very quickly. They are best suitable for high speeds. The weight linked to the torque capacity of the starter motor is very low.

Sings of Bad Starter Motor

As the starter motor goes bad, it gives one of the below-given signs:

  • Engine Won’t Start
  • Whirring, Grinding, or Clicking Noise
  • Intermittent Issues Starting the Vehicle
  • Dashboard lights up, but the engine won’t start
  • Overheating and Smoking

1) Engine Won’t Start

As the starter motor goes bad, your vehicle engine won’t start. The engine won’t start due to many other reasons such as a bad ignition key, damaged solenoid, engine’s internal problems, or failed battery.

2) Whirring, Grinding, or Clicking Noise

The clicking or whirring noise is one of the major symptoms of a bad starter motor. When the starter goes bad, you may hear a clicking noise as you turn the ignition key. As the parts of the starter are worn or don’t work efficiently, you may hear a clicking or whirring similar noise one you notice when the driver accidentally presses the ignition key after starting the engine.

When you hear the whirring, grinding, or clicking noise, you must stop the vehicle and inspect the problem. If your starter has been damaged, you should replace it as soon as possible.

3) Intermittent Issues Starting the Vehicle

If you try to start the vehicle engine and it doesn’t start right away, and then you try again, and it starts, there are high chances that your vehicle starter is faulty. There may be a problem with the starter relay.

If your vehicle starter relay is bad, it will not properly send power to the starter motor. If the relay is faulty, the motor may produce a clicking noise when turning the ignition key.

4) Dashboard lights up, but the engine won’t start

If your vehicle battery is supplying power properly, but the engine is not starting, it means that your vehicle has a bad or damaged starter. Especially if you recently charged your battery.

5) Overheating and Smoking 

The engine overheating is one of the common signs of a damaged or faulty starter motor. The engine overheating leads to an unpleasant smell of smoke inside and around the car. Such a situation indicates that too much current is flowing through the motor.

This overheating issue occurs due to short circuits, ignition switch problems, or other mechanical issues if the starter runs for a long time and the car won’t start.

FAQ Section

What are the symptoms of a bad starter?

When the starter goes bad, it gives one of the below-given signs:

  1. Engine Won’t Start
  2. Overheating and Smoking 
  3. Whirring, or Clicking Noise
  4. Dashboard lights up, but the engine won’t start
  5. Intermittent Issues Starting the Vehicle

What are the causes of a bad starter?

The starter motor goes bad due to multiple reasons. The following are the most common causes of a bad starter.

  • Battery corrosion
  • Oil leakage
  • Engine overheating
  • Damaged or faulty parts of the starter motor
  • Insufficient power supply by the battery
  • Loose wiring to and from the starter
  • Damaged solenoid
  • Bad fuse or relay
  • Corroded connections at the starter end

How do troubleshoot starter problems?

  1. First of all, look under the hood.
  2. Use a hard object and lightly tap the starter for just a few minutes
  3. Now adjust the transmission
  4. Check the fuel gauge

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