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Glow plugs heat the combustion chamber during cold starting and in the first minutes of operation: when they wear out, the diesel struggles to start and produces white smoke.

Typical symptoms

• Long starting at low temperatures
• Thick white smoke on the first strokes
• Rough engine in the first minutes
• Flashing preheat light (stored fault)

How they are tested

• Measuring the resistance of each glow plug (typical values below 2 ohms)
• Reading the faults from the preheat control unit, which often indicates which cylinder
• Checking the supply and the preheat relay

Careful with replacement

Glow plugs seized by carbon can snap during removal: they must be extracted with the engine warm, with specific release products and controlled torque. It is a job best entrusted to someone with the equipment for extraction if needed.

How MasterTuning helps

We check the component with real measurements, not by elimination: flow rates, pressures, corrections and signals read directly from the ECU. We repair, replace and recalibrate the software when needed. Centres throughout Italy.

Read more: vehicle database · what is ECU remapping · find an installer

Want an accurate diagnosis? Contact MasterTuning and book at your nearest centre.

Frequently asked questions

Can you drive with a failed glow plug?

Yes, but with hard cold starts, smoke and greater wear: best to replace it before winter.

Should they all be replaced together?

It is advisable: they are the same age and removal is the most demanding part of the job.

Do glow plugs affect DPF regeneration?

On some engines yes: they contribute to heating the chamber and inefficient preheating can hinder regenerations.