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Glowplugs troubleshooting

Plug appearance
Possible cause
Possible actions
Melted heater tube
Abnormal overheating
  Incorrect fuel injection volume or timing Check fuel injection function
  Excessive lubricating oil entering combustion chamber Check valve guides and piston rings
  Excessive voltage  
  Incorrect glow plug fitted Confirm correct part is fitted
  Faulty control relay, glow plugs 'switched on' for too long. Check controller relay operation
Heating coil broken (coil resistance is infinite). See resistance test below.
Excessive voltage
  Incorrect glow plug fitted Confirm correct part is fitted
  Faulty control relay, glow plugs 'switched on' for too long. Check controller relay operation
Broken heater tube
Excessive turbulence in combustion chamber
  Possibly due to incorrect fuel injection timing or volume flow rate Check fuel injection timing and volume flow rate.
     

 

 

Coil resistance or 'open circuit' test
The diagram below shows a simple 'open circuit' coil test which can be applied to most metal sheathed type glow plugs. The meter is set to measure resistance in Ohms. A measured value of less than 5 Ohm is indicative of an unbroken heating coil. A measured value of more than 5 Ohm (usually extremely high or infinite) is probably indicative of an open circuit and therefore a damaged coil.