Possible causes of malfunction and methods of checking
1. Battery
* Check the battery voltage using a multimeter. It must be at least 12.6 V.
* Inspect the battery for corrosion or damage. Clean the terminals from corrosion.
* Connect the charger and charge the battery (if necessary).
2. Starter
* Try to start the car, listening to sounds from the starter.
*If you hear a clicking sound but the starter does not turn, the solenoid may be faulty. Tap the starter with a hammer to loosen a stuck solenoid.
*If you hear the starter whirring, the starter itself may be faulty.
3. Ignition system
* Check for spark at the spark plugs.
* Remove one spark plug and connect it to the high voltage wire. Place the spark plug on the engine so that the metal body of the spark plug touches the engine. Try starting the car. If there is no spark, the ignition coil, ignition module, or spark plugs may be faulty.
4. Fuel system
* Check the fuel level in the tank.
* Check the fuel filter for blockages. Replace it if necessary.
* Make sure the fuel pump is supplying fuel to the engine.
5. Compression
* Remove the spark plugs and insert a compression gauge into each cylinder. Crank the engine with the starter and record the compression readings.
* Compare the readings with the standard readings for your engine. Low compression may indicate engine wear.
6. Electrical faults
* Check the fuses and relays associated with the starting system. Replace blown fuses and faulty relays.
* Check electrical wiring for damage or loose connections.
* Make sure that the safety switch, if installed, is not turned off.
7. Immobilizer
* Check the condition of the battery in the key. Replace it if necessary.
* Bypass the immobilizer using the spare key (if available).
* Disconnect and reconnect the battery to reset the immobilizer.
If you are unable to determine the cause of the problem yourself, seek help from a trained mechanic.