Engine’s starting system and its problem diagnosis

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To keep the engine running, the engine’s combustion system first needs to get the necessary torque to be started.

The engine’s starting system generates that torque through a starting motor to the crankshaft of the engine.

Once the combustion process starts, the whole system becomes autonomous to keep the system running.

Let’s dive deeper into the explanation-

What is a engine starter motor?

A starter motor is a mechanical device that converts the electrical energy of a battery into mechanical energy.

Through a small pinion gear attached to the end of the starter, the motor transmits that energy to the main crankshaft of the engine.

The engine’s starting system is the process of cranking the engine to initiate the combustion and electric fuel injection (EFI)process.

engine starter motor diagram

How does the engine’s starting system work?

The constituent parts of an engine’s starting system are-

  • Ignition key
  • Battery
  • Starter motor
  • Solenoid
  • Pinion gear
  • Flywheel
  • Alternator

The starter motor is placed in close proximity to the Flywheel. The Flywheel is attached to the end of the crankshaft that has a certain number of teeth in its perimeter.

When the ignition key of a combustion engine is turned on, a good amount of current runs towards the starter motor.

A solenoid attached to the starter motor controls the current by creating an electromagnetic field.

The electricity that is drawn from the battery rotates the pinion gear.

The pinion gear at such a juncture gets connected to the flywheel and starts rotating the flywheel.

The rotation of the flywheel cranks the engine initiating the combustion process.

The pinion gear afterward disconnects from the flywheel, and the combustion process keeps the engine running on its own.

An alternator in the engine’s starting system however keeps the electrical system of a vehicle functional.

An alternator transforms the mechanical energy of the engine into electrical energy. At the same time, an alternator keeps recharging the battery so that the battery can produce essential energy for the starter motor to crank the engine.

engine starting system work diagram

Engine’s starting system’s problem diagnosis

For various reasons, the engine’s starting system may not function properly. Starter failure, pinion engagement error, solenoid failure, and no alternator output are some of the common engine starting system problems that can be solved through diagnosis.

Let’s dissect each of the problems, and how you can solve the issues-

1. The starter fails to operate

Probable reasons


Insufficient battery charge

Charge the battery

High torque in the starting motor control valve

Check battery  connection and cables

Open starter switch or solenoid switch

Ensure a stable cable connection

Broken or damaged brush or low spring tensile

Repairing or replacing the brush and spring

Open field winding or short-circuit

Proper inspection

Open armature winding

Repair or replacement

2. Starter turns but pinions do not engage

Probable reasons


Misaligned armature shaft, pinion, and starter housing

Aligning the shaft, pinion, and starter housing

Faulty switch

Repair or replacement

Closed drive connection

Opening the connection or replacing the drive

Faulty pinion


Weak spring tension

Replacing the spring

Armature spins faster than the engine

Replacing the armature

3. Solenoid failure

Possible reasons


Insufficient storage battery charge

Charge the battery to the right level

Faulty ignition switch

Repairing or replacing the ignition switch

Open control circuit

Inspecting the solenoid, relay switch, and connection

Sticky solenoid plunger

Cleaning the solenoid plunger

Faulty solenoid switch contact


Faulty field winding

Repairing the faulty field winding

4. No-alternator output

Possible reasons


Faulty or damaged armature core

Inspecting the armature ball bearing and replacement if necessary

Ineffective armature bearing

Replacing the bearing

Decayed armature shaft bushing

Replacing the commutator ends

Open or ground alternator stator coil

Adding new coil

Short or open circuit on the alternator rectifier

Replacing the rectifier

Open or grounded transistor, register, or diode short


5. Excessive or over-charge in battery

Possible reasons


Fast engines increase the voltage of the alternator which may cause the electrolytes of the battery to overflow

Stopping the engine

Short or ground on the rotor field winding

Repair or replacement

Faulty regulator

Repair or replacement

The electrolyte level in the battery is low

Filling up the battery with electrolyte

Grounding on the field coil

Repair or replacement after inspecting

Short circuit on the field coil

Inspect through the Avometer and replace it if necessary

6. Diode failure

Possible reasons


faulty voltage regulator

Inspection and replacement if necessary

Lose or damaged alternator belt

Aligning tension or replacing the belt

Faulty alternator

Servicing or replacing the alternator

Burned battery terminal connection

Cut the previous connection and attach a new connection

Faulty heat sink

Repair or replacement

Faulty earthing in the diode or rectifier

Correcting the earthing

Engine’s starting system

Previously, people used to start an engine by using their hands through a handle. But that was near the primitive ages.

Modern combustion engines are more advanced with an electrical starting system.

The engine demands a thrust before it can start the automatic combustion process.

The starting system produces that thrust to transform the electrical energy of the battery into mechanical energy. If you facing any problem with satarting your engine, you can use external jump satarter like nuco jump.

Advantages of the engine’s electrical starting system

  • No external pressure or force is required to crank the engine
  • Troubleshooting is much easier with an electrical starting system
  • Power alignment is electrically controlled
  • The chance of personal damage is much lower
  • Most importantly, an electrical starting system keeps the parts protected from wear and damages

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