A faulty injector cannot be recognised by ear: it is found by measuring return flow, delivery and the per-cylinder corrections read from the control unit. Changing them all "to be safe" is almost always unnecessary and costly.
Typical symptoms
- Rough idle, more pronounced knocking
- Hard starting when hot or cold
- Black or white smoke
- Rising consumption and loss of power
- Error codes on injection corrections or rail pressure
- Oil level rising in the worst cases (diesel in the sump)
The tests that count
- Return flow test: an injector that returns too much fuel is out of tolerance.
- Bench flow test: quantity injected in the different phases.
- Per-cylinder corrections in diagnosis: show which cylinder gets too much or too little.
- Rail pressure check at starting and under load.
Injector or something else? The false clues
The same symptoms also come from the MAF sensor, glow plugs, a blocked EGR or incorrect rail pressure. That is why diagnosis comes before replacement.
After replacement
New or reconditioned injectors must be coded into the control unit with their calibration codes: without coding the engine stays irregular. Costs are in how much it costs to replace the injectors.
How MasterTuning helps
We read the real values of the control unit, not just the code: that is the difference between finding the faulty component and replacing parts by trial and error. After the repair we clear the error and check that it does not come back. Find the nearest centre or contact us.
Want an accurate diagnosis? Book a diagnosis at the nearest MasterTuning centre.
Frequently asked questions
Do additives really clean injectors?
They can help with light deposits, but they do not recover a mechanically worn injector or one with excessive return flow.
Do new injectors need coding?
Yes: each injector has a calibration code to be written into the control unit, otherwise the engine runs rough.
Can only the faulty injectors be replaced?
Yes, if the others are within tolerance on the return and flow tests: they do not all have to be changed.
How do I know which injector is faulty?
With per-cylinder corrections in diagnosis and return and flow tests: a cylinder needing corrections very different from the others points to the injector to check.
