What’s wrong with your diesel?

Tick the symptoms you notice and we’ll point you to where the problem may be. It is a guide, not a diagnosis: only the test bench gives you that.

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[D-03·A]Self-check

Tick what you notice

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Tick at least one symptom

Select what you notice in the car and we’ll tell you where to start.

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Pointer based on common symptoms. Only a bench test confirms the fault.

[D-03·B]Quick guide

Symptom, likely cause and what to do

Symptom	Likely cause	What to do
Black smoke	Injector dripping or spraying badly	Bench-test the injectors
White smoke when cold	Leaking injector or poor spray	Test injectors and glow plugs
Jerking	Uneven delivery between injectors	Bench-test the injectors
Hard starting	Excess return or pump without pressure	Return test and rail pressure
Limp mode	Rail pressure out of range	Check pump, regulator and injectors
Rising oil	Injector dripping diesel into the sump	Test the injectors urgently

[D-03·C]FAQ

What people ask us most

How do I know if an injector is bad?+

The most common symptoms are smoke, jerking, rough idle, hard starting and higher consumption. To be sure it has to be measured on a bench: €15 per injector.

Can I keep driving with a bad injector?+

For a while, yes, but it isn’t wise. A dripping injector can damage the piston or dilute the oil, and the repair gets much more expensive.

Is a return (leak-off) test enough?+

It is a good first clue, but it doesn’t measure injection delivery or spray. A test bench does.