When the starter is turned on, current from the battery begins to flow through the winding of the starter traction relay. The relay armature pulls in and the relay contacts close. At the same time, the relay armature moves the overrunning clutch with the gear through the lever. The overrunning clutch hub also rotates the gear on the screw splines of the starter armature shaft, which facilitates its engagement with the flywheel ring gear. A current flows through the closed contacts of the traction relay, which feeds the stator and armature windings, and the starter armature begins to rotate together with the hub and freewheel.
After starting the engine, the speed of the gear exceeds the speed of the starter armature. In this case, the overrunning clutch turns freely, and torque is not transmitted from the engine flywheel to the starter armature shaft. After releasing the ignition key, the power circuit of the windings of the traction relay opens through the ignition switch, the armature of the traction relay is pressed back to its original position by a spring, the relay contacts open and the drive gear disengages from the flywheel ring gear.
If the starter does not engage when it is turned on, the following reasons are possible:
- battery is defective;
- open circuit between the switch (castle) ignition, traction relay, battery and starter;
- faulty traction relay;
- mechanical or electrical defect of the starter.
To check the battery, turn on the headlights. If their light dims after a few seconds, the battery is low. Recharge or replace the battery. If the headlights do not dim, then turn on the starter and observe the light. If their light dims, then the starter is faulty. If the headlights stay bright (and there is no click of the starter traction relay) - the electrical circuit is damaged or the traction relay is faulty. If the starter rotor rotates slowly, and the battery is good and charged, then the starter is defective or there is an open in the starter electrical circuit.
To check for damage in the electrical circuit, disconnect the battery and clean all connections and contacts in the starter power circuit. Reconnect the battery and use a voltmeter to check the voltage through the elements of the electrical circuit to the starter.
If the battery is good and the electrical circuit is not damaged, remove the power wire from the traction relay and connect a voltmeter to it. Turn the ignition key to position «Engine start». In this case, the voltmeter should show the voltage of the battery.
The contacts of the traction relay can be checked by connecting a voltmeter between the contact of the traction relay connected to the starter, and «weight». When the key is turned to position «Engine start» The voltmeter should show voltage. In the absence of voltage, the traction relay is faulty or its contacts are burnt.
If the electrical circuit and the traction relay are working, the starter is faulty.