Glow Plugs

With 167 parts covering more than 8,000 applications, discover why DENSO glow plugs are the OE industry standard.

Glow Plugs

How DENSO glow plugs work

Improving the emissions standards of diesel engines is an increasing priority. Glow plugs play a key part in minimizing the environmental impact of diesel emissions, alongside ensuring engine reliability and performance. To start combustion within a diesel engine, air is compressed in a chamber to raise the temperature and pressure, fuel is then added to this air to start the combustion cycle, providing power to the engine.

If the temperature of the air is too low, then some of the fuel that is supplied may not be burnt. Unburnt fuel then turns into carbon and is released via the exhaust, causing environmental damage. To minimize the amount of unburnt fuel, glow plugs provide extra heat to the air and ensure that the combustion chambers reach the required temperature for a clean combustion cycle.

The engine management system (EMS) can also trigger glow plugs to provide heat to the diesel particulate filter (DPF) which burns toxic soot particles before they leave the exhaust in a process called diesel particulate filter (DPF) regeneration. This burns the soot particles, meaning it won’t have an adverse effect on the environment.

Overall Glow Plug image

Features and benefits of DENSO glow plugs

  • Manufactured to meet or exceed OE specifications.
  • Reliable temperature control, including faster heat-up times.
  • Suitable for use in almost any European diesel engine.
  • Proven to reduce a vehicle’s carbon emissions impact.
  • Manufactured with highest quality standards and precision
OE standard quality
By making significant investments into research and development, we’ve created innovative glow plug designs that meet or exceed industry standards.
Reliable temperature control
With a reliable rapid start, even in sub-zero temperatures, DENSO glow plugs heat up fast and stay at a high temperature for longer, helping to reduce carbon emissions.
Easy-to-access parts
DENSO products cover more applications with fewer part references. Plus, an easy-to-use part numbering system helps manufacturers find the right part quickly and easily.
Glow plug packaging showing different sizes

Types and characteristics

Whatever your application or vehicle type, DENSO glow plugs provide efficiency and optimum performance that makes us a long-standing leader in the European aftermarket.

Glow Plugs types

Instant heating

Our market-leading double coil technology provides instant heating and a self-regulating resistor that enables quick engine start-up and reduces noise, vibrations and emissions.


As the first OE manufacturer of ceramic glow plugs, the conductive nature of the material means the all-ceramic design can reach and maintain high temperatures for longer.

Double coil

With two serial resistors inside, one acts as a regulator to ensure improved temperature accuracy and enabling the glow plug to reach hotter temperatures in a shorter time.


Our OE standard glow plugs are proven to provide high-temperature performance quickly with greater temperature accuracy, ensuring long-lasting ignition performance every time.

Catalogues and leaflets

To find out more about Glow Plugs browse the Downloads Area section. Click here.

Installation and fault finding

Installing your glow plug correctly and ensuring any faults are fixed quickly will help you to maintain their performance for a longer lifetime.


Install your glow plug quickly and easily:
  1. Use the correct wrench for the glow plug and terminal.

  2. When changing the glow plug, make sure that oil, dirt etc. on the outside of the disassembled glow plug does not enter into the cylinder.

  3. When mounting the glow plug, clean the engine side of the flange and make sure the glow plug is correctly in line with the thread of the cylinder head.

  4. Make sure the plug is correctly positioned and tighten it by hand until it cannot be tightened any further.

  5. Then, use a torque wrench to tighten it accurately to the relevant torque.

  • DO NOT USE A THREAD LUBRICANT! If a thread lubricant such as grease is coated on the tread, the resistance between the glow plug and the cylinder head will be less, resulting in overtightening.

  • Tightening more than the recommended torque could result in damage to the glow plug and engine.

  • Glow plug failure is most commonly caused by excessive voltage and/or heat. Glow plugs are designed to operate between 850 to 1100 degrees. When the electrical current to the glow plug is held too long, either because of a faulty relay and/or controller, it can lead to overheating which will cause the glow plug to swell, split or burst and cause immediate failure. Therefore it is advisable to check out the entire ignition electrical system before changing to new glow plugs. Overly advanced injection timing, leaky injectors, or diesel running in your engine will cause the combustion temperature to increase too much, damaging the glow plugs. A faulty relay and controller can also cause glow plug failure, so it is advisable to check out the entire system before changing to new glow plugs.

Fault finding

Finding faults quickly will help to minimize engine damage:

The most commons symptoms of a glow plug fault include:

  • An engine warning light is the first indicator that there could be a fault in your glow plug or heat temperature sensor.

  • A hard starting engine, especially in cold conditions. This suggests that your glow plugs aren’t warming up quickly enough.

  • If your diesel engine starts to misfire, this is an indicator that the combustion process isn’t working properly which can involve a fault with the glow plug or fuel injection system.

  • If your engine starts to idle and white smoke comes from the exhaust, this could indicate that your glow plugs have burned out.

  • Black smoke coming from the exhaust or reduced fuel efficiency can be indicators of glow plug faults.

The most common faults in a glow plug include:

  • Enlarged probe tips caused by excessive voltage passing through the plug.

  • Broken probe tips, also caused by excessive voltage.

  • Swollen probe tip.

  • Holes, cracks or probe melting, which can be caused by a variety of problems, including a failure in the ignition unit.

  • Carbon present on the tip, usually caused by unburnt fuel leading to carbon accumulation on the tip/body of the glow plug

  • A missing probe, caused by a failure in the glow plug relay, or the glow plug being insufficiently tightened during installation. Failure in glow plug relay can lead to excess voltage being provided to the glow plug, thus overheating the probe and initiating cracks

  • Bent or broken power terminal, caused by overtightening during installation.