Before diagnosing the starter, make sure the battery is fully charged.
1. If the starter does not turn at all when you turn the ignition key, make sure the gearshift lever is in the "N" or "P" position (automatic transmission) or, if provided, the clutch pedal is pressed (manual transmission).
2. Make sure the battery is charged and that all wires at both the battery terminals and the traction relay terminals are clean and secure.
3. If the starter rotates but the engine does not turn over, the starter overrunning clutch is slipping and the starter must be replaced.
4. If the starter does not rotate when you turn the ignition key, and the traction relay makes a clicking sound, then the problem is either in the battery, or in the traction relay contacts, or in the starter itself (or the engine is jammed).
5. If you do not hear the action of the traction relay plunger when turning the ignition key, the battery is faulty, the ignition switch is defective, or the fuse wire is burnt out (chain break) or the traction relay itself is faulty.
6. To check the traction relay, connect a jumper between the battery (+) and the traction relay enable terminal (small terminal). If the starter now works, then the traction relay is OK and the problem is in the ignition switch, starter inhibitor switch (models with automatic transmission), clutch switch (some models with manual transmission) and in the wires.
7. If the starter still does not work, remove the traction relay/starter assembly for disassembly, inspection and repair.
8. If the starter turns the engine at an abnormally slow speed, first make sure the battery is charged and all terminals are tight. If the engine is seizing or the wrong viscosity oil is used, the engine will turn over slowly.
9. Warm up the engine to normal operating temperature, then disconnect the high-voltage wire of the ignition coil from the distributor cap and connect it to the housing.
10. Connect the positive probe of the voltmeter to the positive terminal of the battery and the negative probe to the negative terminal.
11. Crank the engine and read the steady state voltmeter reading. Do not allow the starter to crank for more than 10 seconds without stopping. Normal voltage is 9 volts or more when the starter is cranking the engine at normal speed. If the reading is 9 volts or more but the cranking speed is low, the starter is faulty or there is a problem with the battery (faulty or discharged).
This article is based on information from the website «www.bmwman.ru»