Fault Finding Glow Plugs and what they mean

Opie Oils and our friends at Denso have come together to help you understand the faults you might find your glow plugs in. Ensuring your glow plugs are functioning correctly is an important part of keeping your engine in good health. But how can you tell the difference between a plug that’s doing its job and one that’s on its last legs? Well, the appearance of the probe tip of a used glow plugs directly reflects the condition of an engine.

A little history about Denso. In 1991 Denso is the first OE Manufacturer of Ceramic Glow Plugs, improving starting performance and reducing emissions.

In 1995 Denso pioneers the world’s first Diesel Common-rail system optimum injection pressure for maximum performance, quality and reliability.

In 2005 Denso introduces the world’s first 1800-bar Diesel Common Rail fuel system with highly responsive injectors, providing even better combustion performance.


Enlarged Probe Tip

Causes

  • Excessive Voltage
  • Failure of Alternator and Regulator
  • Dampness Durning Storage

Solution

  • Check onboard and Glow Plug voltage
  • Check charging system
  • Check quality of storage conditions

Broken Probe Tip

Causes

  • Excessive Glowing or Voltage
  • Failure of Alternator and Regulator

Solution

  • Check contacts on glow plug regulator
  • Check onboard and Glow Plug voltage
  • Check charging system voltage

Damaged or Missing Probe Tip

Causes

  • Failure of Ignition unit
  • Direction or regularity of fuel jet incorrect
  • Sealing fault causing spraying position error

Solution

  • Check the ignition unit is correctly installed
  • Check you are using the correct ignition unit for the vehicle model
  • Check the Glow Plug installation point for carbon deposits

Deformed Probe (Overheating)

Causes

  • Failure of ignition unit
  • Direction or regularity of fuel jet incorrect
  • Wrong spraying position caused by faulty sealing
  • Excessive Glowing or Voltage
  • Failure of alternator and regulator
  • Function or timing fault in injection unit

Solution

  • Check the ignition unit is correctly installed
  • Check you are using the correct ignition unit for the vehicle model
  • Check the Glow Plugs installation point for carbon deposits
  • Check contacts on Glow Plug regulator
  • Check onboard and Glow Plug voltage
  • Check Charging system voltage
  • Check fuel Injection timing

Swollen ring on the probe Tip

Cause

  • Oil in the combustion chamber

Solution

  • Check piston clearance in engine cylinders
  • Check oil consumption

 


Missing Probe

Cause

  • Ignition Unit Failure
  • Direction or regularity of fuel jet incorrect
  • Wrong spraying position caused by faulty sealing
  • Function or timing fault in injection unit
  • Tread damage to opening of cylinder head where Glow Plug is installed
  • Glow Plug insufficiently tightened causing plug to sit incorrectly

Solution

  • Check you are using the correct ignition unit
  • Check the ignition unit is correctly installed
  • Check the Glow Plugs installation point for carbon deposits
  • Check timing of injection pump
  • Check the opening of cylinder head

Probe touching body of glow plug

Cause

  • Over tightened torque
  • The wrong tool used
  • Thread damage to opening of cylinder head

Solution

  • Check the Opening of cylinder head for damage
  • Check Glow Plug torque

Holes, cracks or melting next to body of Glow Plug

Cause

  • Failure of ignition unit
  • Thread damage to opening of cylinder head where Glow Plug is installed
  • Glow Plug insufficiently tightened causing plug to sit incorrectly

Solution

  • Check timing of injection pump
  • Check the opening of cylinder head for thread damage

Carbon deposits between probe and body of Glow Plug

Cause

  • Failure of ignition unit
  • Direction or regularity of fuel jet incorrect
  • Wrong spraying position caused by faulty sealing
  • Injection Pump operation failure

Solution

  • Check you are using the correct ignition unit for vehicle model
  • Check the ignition unit is correctly installed
  • Check the Glow Plug installation point for carbon deposits
  • Check the Opening of cylinder head for carbon fouling
  • Check timing of injection pump

Broken or Bent power terminal

Cause

  • Over tightened torque
  • The wrong tool used
  • Thread damage to opening of cylinder head

Solution

  • Check the opening of cylinder head for damage
  • Check Glow Plug torque

If you’re wondering how often should you change your Glow Plug, Opie Oils are sorry to say there is no single simple answer to this question.  The best guide is the manufacturer’s recommendation for your vehicle, as this particular service varies from manufacturer to manufacturer and brand to brand.

We understand Glow Plugs can be very confusing and if you are still new to Glow Plugs or have never thought about changing them before, finding the correct can be difficult.  Opie Oils are here to help. You can give us a call on 01209 202 944, drop us an email to sales@opieoils.co.uk or even send us a message on here. We’ll answer as quickly as possible, we’re in the office Monday to Friday 8:30 – 5:30.

That’s all from us today

Opie

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