Not every engine problem shows up in exhaust temperatures or peak pressure values.
During a planned diagnostic inspection of a Daihatsu 6DK20 Auxiliary Engine, we performed Advanced Combustion Engine (ACE) measurements, combining combustion pressure analysis with high-frequency vibration monitoring.
At first glance, everything appeared normal.
✅ Exhaust gas temperatures were balanced
✅ Peak pressure values remained within limits
✅ No alarms or obvious operational issues were reported
But the advanced measurements told a different story.
📊 When analyzing the combustion and vibration traces around Top Dead Centre (TDC), we noticed an abnormal injector signature.
The high-frequency vibration pattern associated with fuel injection was significantly weaker than expected, while the combustion pressure curve indicated less efficient fuel delivery.
These subtle indicators pointed toward a likely problem:
👉 Injector nozzle contamination or wear.
Based on the measurements, we recommended:
🔧 Checking and cleaning the injector nozzle
🔧 Verifying injector opening pressure
The crew carried out the inspection and confirmed our diagnosis.
✔️ Carbon deposits were found on the injector nozzle tip
✔️ Injector opening pressure was below specification
✔️ The injector was cleaned, overhauled, and readjusted
This case highlights an important lesson:
Traditional indicators such as Pmax and exhaust temperatures can remain perfectly acceptable while combustion quality is already deteriorating.
Without advanced diagnostics, this issue could easily have gone unnoticed until performance losses or more serious damage occurred.
✅ Problem detected early
✅ Unnecessary dismantling avoided
✅ Time and maintenance costs reduced
Because effective diagnostics isn’t about finding failures.
It’s about finding the problems that haven’t become failures yet.
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