Car Starter or Starter Motor Problems.


The Starter Motor Problems, which usually occur in the starting motor, are as follows:

(a) Starting motor does not turn to crank the engine.

 It may happen due to the following possible causes:

  1. Discharged or defective battery.
  2. Too high resistance in the starting motor or control circuits.
  3. Open circuit in starter switches.
  4. Open or short-circuited armature.
  5. Open or short-circuited field windings.
  6. Wrong starting motor brushes.
  7. Broken or weak brush springs.
  8. Tight armature shaft bearings.
  9. Locked starter motor drive.
  10. Hydrostatic lock due to some interference with the engine piston movement.
  11. Excessive friction in the engine.
Starter Motor Problems
Starter Motor

(b) Starting motor cranks the engine slowly.

It may happen due to the following possible causes:

  1. The too-high viscosity of engine oil.
  2. Causes 1, 2,4,5, 6,7,8 of section (a).

(c) Starting motor spins but does not crank the engine.

It may happen due to the following possible causes:

1.Defective drive due to the jammed drive assembly, misaligned gears, clogged thread sleeve, defective switch, etc.

(d) Starter gear fails to disengage when the engine starts.

 It may happen due to the following possible causes:

  1. Defective starting motor drive due to clogged sleeve threads, broken springs, slipping clutch, misaligned pinion gear, broken teeth.
  2. Ruined starting motor.

Diagnosis of Starter Motor (Starter Motor Problems)


In the event of the starter motor fails to crank the engine at a high engine speed to allow it to start, first check the state of charge of the battery, tightness, cleanliness and all the heavy-duty electrical joints.

This usually solves most of the starting problems. If the slow speed cranking still persists or the starter motor fails to function at all, it is necessary to remove the unit from the engine. After its removal from the engine, a simple functional check can be made on the solenoid switch and the motor separately. To check the solenoid, connect the one lead from a 12 V battery to the supply terminal and the other battery lead to the body of the starter. This should cause the starter drive to move along the armature shaft. If an ammeter is put in series with the solenoid and a connection also made between the solenoid terminal and top main terminal, then with 12 V applied, the ammeter should read approximately 20 A. when the drive is fully engaged.

Starter Motor Problems
Car Starter

A high current reading (40 A) or failure of the drive to move at all, means the solenoid is faulty and should be returned to a recognized LUCAS SERVICE CENTRE for rectification or replacement. A direct light run check can also be made on the starter at this time.   The starter motor should rotate freely at 5000-7000 RPM. and take a maximum current of 100 A. If the motor fails to rotate, is sluggish or takes a high current, it should be returned to a recognized LUCAS SERVICE CENTRE.

During this test, the band cover around the tarter yoke may be removed by loosening the single bolt fixing. Excessive sparking indicates that commutator or brushes may need attention. If just dirty, the commutator can be cleaned with a petrol moistened rag. Similarly, dirty or sticky brushes in the brush holders should be cleaned. A badly grooved commutator will require re-skimming with the correct equipment, but it is not necessary to undercut to commutator slot insulators. If prior to removing the starter from the engine, the starter rotates but the engine does not, this indicates either a sticky or faulty roller clutch drive.

The subsequent solenoid check will reveal whether the drive is sticky on the shaft and a simple hand check can be made on the drive itself. It should be possible to freewheel the drive pinion in a clockwise direction, but the whole armature should rotate when the pinion is turned anti-clockwise. If the pinion rotates freely in both directions, the drive will need to be replaced as a unit. Similarly, if the drive slips under load, replacement is also necessary, the fault, however, is unusual.


Two different types of electric starting motors are used for commercial vehicles, namely the Non-axial Starter and the Axial Starter. Usually, these are similar in regard to certain electrical details, like the armatures and brush gear, so that the general information on their maintenance is applicable for such items for both types.

Car Starter
Starter Motor Problems

Also, Read These Posts

  1. What is Over-Running Clutch Drive? Applications Of Over-Running Clutch.
  2. What is Folo-Thru drive?
  3. What is Starter Motor? Construction and Operation of Starter Motor.


Creative Blogger And Automobile Engineer.

Leave a Reply

Your email address will not be published. Required fields are marked *