How to repair the starter, what can be the causes of breakdown?

Although the starter is quite reliable and operates for short periods of time, it can also break down. The lifespan of many parts of the starter depends not on the total mileage of the vehicle, but on the number of starts. Causes of starter failures are failures related to the following:

• electric motor;
• drive;
• pull relay.

What fails most often?

Breakdowns related to the starter and starter system instruments:

• worn electric motor armature bearings;
• greasy and worn brushes, collector;
• brush holders and housing short-circuited
• brush holder springs have weakened;
• twist short circuits in the winding or winding breakage;
• incorrect operation of moving parts of the drive, slippage, clutch jamming;
• winding breakage in the traction relay

For more information about motor faults

Wear of the armature bearing happens due to prolonged use of the starter, which leads to unbalance of the armature, and as a consequence – multiple breakdowns. For this reason, it is necessary to monitor the condition of the bearings and replace them, even if the repair is due to other reasons.

Leaks of technical fluids in the underhood cause the brushes and collector to become greasy. As a result, the resistance in the winding circuits of the electric motor will increase, causing the motor to lose power.

Worn brushes and collector reduce the force of the brushes against the collector. Insufficient contact can increase sparking, electrical erosion will develop more intensively. In addition, metal-graphite dust, which is caused by worn brushes, causes the brushes to short-circuit the housing and the starter motor will stop working.

The brush holder springs become loose when the starter is switched on for long periods of time, due to overheating. This failure causes the brushes to become weak against the collector, resulting in increased sparking.

Faults in the windings and armature, inter-turn shorts in the winding occur due to thermal damage to the insulation, which becomes brittle and can quickly break down.

It should be noted that field winding (FW) and armature-to-case faults are considered in the case of electrically excited generators.

Drive failures

Jamming of the moving parts of the drive on the armature shaft due to contamination of the splines and scaling of the shaft housing from wear of the sleeve bearings.

Drive failure

Damage to the drive gear teeth is most often caused by incorrect repairs. For example, when the starter has been removed and then installed in a skewed condition, or the bolts have been poorly tightened and the fasteners loosened.

Roller clutch slippage can occur due to worn rollers and gear hub grooves due to contamination inside the clutch.

Roller clutch jams because the starter is not disengaged in time, when the engine has already started and the starter is still running. If the clutch is jammed, the armature speed increases after the engine starts, which leads to the armature being spun out.

Traction Relay Failures

Oxidation and burning of the contact surfaces of the power terminal bolts and contact discs of the traction relay due to spark formation at the moment of current breaking when the electric circuit is switched off. Due to oxidation, the current and power of the electric motor are reduced. The motor shaft speed is reduced or the shaft does not rotate at all.

Traction relay windings break in the areas where the winding is soldered to the relay terminal. If a winding break occurs, the relay will not operate.

If the retaining winding is broken, the flywheel pinion gear will repeatedly engage/disengage with the flywheel crown, accompanied by the characteristic frequent and sharp thumping.

Closure

If there is a failure in the starter, it will «pull» other faults that can cause complete starter failure. The greatest danger to the starter – long and uninterrupted attempts to start the motor. With prolonged switching on, the winding heats up, brushes, collector and retractor relay – burn out.

For this reason, for any abnormalities in the operation of the starting system, it is better to diagnose the starter. Especially since with the MS016 tester this can be done quickly and directly on the car. After connecting the MS016 tester to the starter and briefly starting the engine, the tester will display a graph of changes in key electrical parameters. This information can be used to determine if there are any abnormalities in the starter, battery or wiring.