Starter Motor Overhaul

Starter Motor Overhaul

Blog Article

Starter Motor Overhaul

Signs Indicating the Need for an Overhaul

1. Weak or No Cranking: If the engine cranks slowly or fails to crank at all when the ignition key is turned, it could be a sign of a problem with the starter motor. This may be due to worn - out brushes, a faulty solenoid, or issues within the motor's electrical windings.


2. Unusual Noises: Grinding, clicking, or screeching noises during the starting process often indicate problems such as a misaligned or worn - out drive gear (pinion gear), damaged bearings, or issues with the solenoid's operation.


3. Electrical Issues: Flickering lights on the dashboard or a rapidly draining battery when attempting to start the engine can suggest that the starter motor is drawing excessive current, which could be caused by internal short - circuits in the motor's windings or a problem with the brushes and commutator.

Disassembly Process

1. Safety First - Disconnect the Battery: Before beginning any work on the starter motor, it is essential to disconnect the vehicle's battery. This prevents the risk of electric shock and accidental activation of the starter motor during the overhaul.


2. Remove the Starter Motor from the Engine: The location of the starter motor varies depending on the vehicle's make and model. Generally, it is mounted on the engine block, near the flywheel or flexplate. Remove the electrical connections, typically the power cable from the battery and the control wire from the ignition switch. Then, remove the mounting bolts that secure the starter motor to the engine block.


3. Disassemble the Starter Motor Components:
   
   
   
   • Solenoid Removal: The solenoid is usually attached to the starter motor housing. Remove the bolts or screws that hold the solenoid in place. Some solenoids may also have a plunger or a shift fork that needs to be carefully disengaged.
   
   
   • Brush Plate and Brushes: Remove the screws or clips that hold the brush plate in place. The brush plate contains carbon brushes that make contact with the commutator. Gently remove the brushes, taking note of their position and spring tension. Brushes are often worn down over time and may need replacement if they are significantly shorter than their original length.
   
   
   • Armature and Field Coils: After removing the brush plate, the armature can be pulled out of the starter motor housing. The armature consists of a laminated iron core with windings. Inspect the armature for signs of damage, such as burnt windings, broken wires, or excessive wear on the commutator. The field coils, which create the magnetic field in the motor, are also part of the housing and may need to be examined for any signs of short - circuits or damage.
   
   
   • Drive Mechanism: The drive mechanism, including the pinion gear and the one - way clutch, should be disassembled. The pinion gear is responsible for engaging with the flywheel. Check for worn - out teeth on the pinion gear and ensure that the one - way clutch allows the pinion gear to rotate in one direction (towards the flywheel for starting) and locks to transfer torque, but slips when the engine starts and tries to over - speed the starter motor.
   
   
   
   

Component Inspection and Repair

1. Brushes: Measure the length of the brushes. If they are worn down to less than the manufacturer - specified minimum length, they should be replaced. New brushes should be installed, ensuring proper alignment and that the springs provide the correct amount of tension to keep the brushes in contact with the commutator.


2. Commutator: The commutator is the segmented copper ring on the armature shaft that the brushes contact. Inspect the commutator for signs of pitting, burning, or uneven wear. If the commutator is dirty or has a thin layer of carbon deposits, it can be cleaned using a fine - grit sandpaper (such as 600 - grit) or an electrical contact cleaner. If the wear is more severe, the commutator may need to be turned on a lathe to restore its smooth surface.


3. Armature Windings: Use a multimeter to test the armature windings for continuity and shorts. If there is an open circuit (no continuity) or a short - circuit between the windings, the armature may need to be rewound or replaced.


4. Field Coils: Similarly, test the field coils for continuity and shorts. If a field coil is damaged, it may need to be replaced. In some cases, if the problem is a loose connection, it can be repaired by soldering the wire back in place.


5. Drive Gear and One - Way Clutch: Examine the teeth of the pinion gear for wear or breakage. If the teeth are damaged, the pinion gear should be replaced. Test the one - way clutch by rotating the pinion gear in both directions. It should rotate freely in one direction (when the starter motor is cranking) and lock in the other direction (when transmitting torque to start the engine). If the one - way clutch fails this test, it needs to be replaced.


6. Solenoid: Test the solenoid using a multimeter. Check the resistance of the solenoid's coils and ensure that the contacts close and open properly when an electrical current is applied. If the solenoid is faulty, it should be replaced.

Reassembly

1. Lubrication: Apply a suitable lubricant to all moving parts, such as the bearings, the drive shaft, and the pivot points of the solenoid's plunger. Use a high - quality grease that can withstand the high - temperature and high - torque conditions within the starter motor.


2. Install the Armature: Carefully insert the armature back into the starter motor housing, ensuring that it is properly aligned.


3. Install the Brush Plate and Brushes: Place the new brushes in the brush plate and install the brush plate back onto the starter motor housing. Make sure the brushes make good contact with the commutator.


4. Reinstall the Solenoid: Attach the solenoid back to the starter motor housing, reconnecting any wires or connectors. Ensure that the solenoid's plunger and shift fork are correctly positioned.


5. Reattach the Drive Mechanism: Install the one - way clutch and the pinion gear back onto the drive shaft. Make sure the drive mechanism is properly assembled and that the pinion gear can move freely in and out to engage with the flywheel.


6. Mount the Starter Motor Back on the Engine: After reassembling the starter motor, mount it back onto the engine block. Reconnect the electrical cables, first the power cable from the battery and then the control wire from the ignition switch.

Testing

1. Bench Testing: Before reinstalling the starter motor on the vehicle, it can be bench - tested. Connect the starter motor to a suitable power source (such as a battery of the correct voltage) and a switch. When the switch is closed, the starter motor should spin smoothly and quietly. Check for any abnormal vibrations or noises during this test.


2. In - Vehicle Testing: Once the starter motor is reinstalled on the vehicle, reconnect the battery. Try starting the engine. The engine should crank smoothly and start quickly. Monitor for any signs of problems, such as slow cranking, unusual noises, or electrical issues. If the engine still does not start or there are persistent problems, further troubleshooting may be required.