Fault finding

A malfunctioning starter can display a range of different symptoms. It may rotate but not crank the engine, or rotate too slowly. It may be making an abnormal noise that needs investigation. Or it may not rotate at all, perhaps accompanied by a noisy or silent magnetic switch. The following scenarios will help you to diagnose the problem with the starter circuit, assess the possible causes and take the right action. Always refer to the appropriate Vehicle Manufacturer's service manual, however, for specific information relating to starting system diagnostic procedures and safety precautions for that vehicle.

1. Does the starter turn the engine too slowly? 
  • Make sure the battery is fully charged (12.6 volts) and the battery cables and terminals are in good condition.
  • Advanced engine timing will produce combustion forces working against engine rotation. These forces will be transmitted to the starter during starter engagement, reducing the starter's performance capability.
  • Excessive engine oil viscosity, particularly in cold weather environments when the oil's viscosity is greatly affected, will reduce the ability of the engine to rotate. This increase in engine drag will be transmitted to the starter during starter engagement, reducing the starter's performance capability.
  • Engine modifications change the operating characteristics of the engine. If modifications are performed, a chance of additional forces acting against the starter will be introduced. The starter should be replaced with one meeting the new operating characteristics of the engine.
  • Another cause can be poor contact of the magnetic switch contact or alternatively there may be a motor assembly malfunction (eg layer short, brush wear); or there may be engine damage.
2. Does the starter fail to crank the engine? 
  • The starter is designed to turn at a specific number of revolutions per minute (RPM). If the battery connections or cables are corroded or dirty, this will cause the starter to turn slower than the specified RPM. Be sure that all battery connections and cables are clean and secured properly
  • Other causes could be that the pinion gear does not engage with the ring gear. Alternatively there may be a sliding clutch or a locked engine.
3. Does the starter turn without turning the engine? 
  • The flywheel or flexplate transfers the rotational energy of the starter to the engine. If the starter is turning but not the engine, check all the teeth on the flywheel/flexplate to see if they are excessively worn, damaged or missing. Inspecting the flywheel/flexplate teeth can be performed through the starter mounting port if an inspection plate is not available. Check all the teeth on the flywheel/flexplate.
  • A failed starter drive assembly could produce similar symptoms as a damaged flywheel/flexplate. If the starter pinion meshes properly with the flywheel/starter and does not rotate, the starter should be inspected for mechanical wear or damage.
  • The starter maybe installed upside down. Check the installation instructions.
4. Does the starting system click when activated? 
  • If clicking is heard when activating the starter control circuit and the starter does not turn, the solenoid may not be receiving the voltage necessary to be activated fully.  Check the starter control circuit wiring for damaged, loose, dirty or corroded connections.
  • If the solenoid is receiving proper voltage, the solenoid may have burnt contacts.  Follow the vehicle manufacturer's recommended procedures and safety precautions to inspect the solenoid.
  • Check battery voltage.  Recharge or replace if necessary.
5. Is there a clattering noise when trying to start the engine? 
  • Clattering may be associated with physical damage to the flywheel/flexplate.  Inspect the flywheel/flexplate completely for cracks, dents, roundness balance etc.
  • An inoperable starter solenoid or a damaged starter may also cause clattering. Follow the vehicle manufacturer's recommended procedures and safety precautions to inspect the solenoid and starter.
  • The battery must be fully charged (12.6 volts) as per the battery manufacturer's recommendations, and the battery cables and terminals in good, clean condition.
  • Other reasons for abnormal noise from the starter may also be due to abnormal brushing, wear on the pinion gear / ring gear teeth tips or poor pinion gear sliding or engagement.
6. Does the starter not turn at all? (with no noise from the magnetic switch) 
  • The battery may have poor specific gravity and level; in which case inspect the battery.
  • There may be a poor starter switch circuit connection of contact or alternatively there may be a malfunction of the magnetic switch pull-in coil or plunger.
7. Does the starter not turn at all? (but the magnetic switch makes a noise) 
  • The battery may have poor specific gravity and level; in which case inspect the battery.
  • There may be a poor start-up circuit contact or there may be a motor assembly malfunction (e.g. layer short, brush wear).