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.
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.
Worn-out glow plugs: symptoms and how they are tested: what are the symptoms?
The most common symptoms are: long starting at low temperatures; thick white smoke on the first strokes; rough engine in the first minutes; flashing preheat light (stored fault).
