The start system converts electrical energy from the battery to mechanical energy to turn the engine over (complete Revolution). A malfunction within the starting system will make it difficult for the engine to run.

Parts of the self-start system 

Ignition switch or start button, a Neutral Safety Switch, Starter Solenoid, Starter Motor, and the Battery (may be used more than one).

1. Neutral safety switch

A neutral safety switch is a device installed on automatic transmission vehicles to ignite the engine. Transmission is in the gear.

2. Starter solenoid

An electromagnet’s primary function is to actuate the starter motor an internal combustion engine with the help of a contractor by which battery is connected to the starter motor. If the solenoid fails, the starter motor wouldn’t work or in other means, the engine wouldn’t crank or starts when you turn on the ignition key.

3. Ignition Switch

a switch using which the engine of the motor valve may be stopped or started.

4. Starter motor

Electrical device that is used to rotate the crank of the internal combustion engine to initiate the engine operation under the range of its own power (starter motor can be electrically, pneumatically, or hydraulically).

How to Work Self Start Mechanism

When the ignition key is pressed for self-start operation of an engine. Transmission should be a park or neutral state. The battery voltage is passed through the starter control circuit to activate the solenoid.

  • The starter motor is powered by the solenoid which helps the starter gear forward to engage with the engine flywheel. This flywheel is placed (mounted) over the engine crankshaft.
  • As the starter motor spins, it turns the flywheel to with the crankshaft, as the engine starts system disengages (release or separate) from the flywheel.

Note: automatic transmission, the starter motor can be operated when the vehicle is in the park or neutral positions, and in manual transmission, the clutch pedal must be depressed.

Symptoms of a bad failing motor

1. Engine wouldn’t crank or start

This is one of the common signs of motor that occurs it may be due to falling battery, bad ignition switch or engine mechanical problem.

2. Slow cranking

If you notice your engine cranking slowly is mainly of a weak battery or internal engine problem.

3. Grinding noise

Grinding noise means the teeth on the starter pinion are damaged.

4. Whirring noise

A whirring is detected when starter pinion gear freewheels during the engine cranking. The pinion gear is not engaging the flywheel properly, which also causes the engine to fail to starts.


cause of failures: A self-start system may have the following malfunctioning ways

  • The electrical connection is faulty.
  • Solenoid switch stiff or faulty.
  • Single pinion gear, starter pinion, or freewheel damaged.
  • Electrical motor damaged by electrical.

Note: a fault-free supply of power to the starter is a must for its proper function. The vehicle battery and the positive, ground supply of starter devices should be included in the fault diagnostics column.

Click Here To See Difference Between Electric Motors And Generators

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