The performance of a fuel injector is effected by both wear and the quality of build. Most automotive fuel injector nozzles have a manufacturer replacement recommendation in the region of 60,000 miles - many injectors will give satisfactory performance for far longer than this although performance with different fuels can vary.
Due to insufficient quality control some new injector nozzles, from established injection equipment manufacturers, have been found to under perform. For this reason it is recommended to thoroughly test new injectors or injector nozzles before fitting.
When examining injector performance particular care should be taken to ensure that needle seat leak by is well within manufacturers specification. With mechanical injection systems carefully adjusting the injector opening pressures to the same value ensures that fuel injection timing is consistent from one cylinder to the next.
Ensuring that the engine temperature regulation is operating correctly provides confidence that temperatures within the engine reach that necessary for good combustion. On a liquid cooled engine such a check would include checking, and if necessary replacing
Unburnt fuel can migrate past the piston into the engine lubricating oil. Oil analysis labs will complete thorough testing of the engine oil. Some simple tests can be performed to asses oil contamination.
A drop of oil is placed onto blotting paper or a business card which is supported in a horizontal position, not resting on a surface. After six hours the blotter is examined.
A sample of used oil is placed in a fridge for 8 hours. When the sample is tipped it should flow. The sample may be much thicker. If the sample wobbles like jelly it suggests that the oil is polymerising due to fuel contamination. If the sample continues to wobble when it has returned to room temperature fuel contamination is severe.
Things you can do to get maximum engine life from a PPO converted diesel
| License | CC-BY-SA-3.0 |
|---|---|
| Cite as | Darren (2007–2025). "Engine health check". Appropedia. Retrieved September 28, 2026. |