Fuel Contamination

“Water and Sediment contamination of Diesel is a Fact of Life”, diesel fuel is a complex product; its primary use is as a fuel, however, its other functions are for lubricating and cooling the fuel injection equipment.

Condensation, poor fuel supplies, poor fuel storage and bad housekeeping all play a significant part in diesel fuel contamination.

Fuel Injection pressures and cleanliness requirements are far different today than from just a few years ago. Mechanical Pump Systems commonly operated at pressures from 10,000 – 14,000 psi.

Today, increasingly rigorous exhaust emission standards have driven injection pressures to exceed 40,000 psi. While these very high injection pressures improve fuel atomisation and reduce emissions, they also cause dramatically accelerated fuel system abrasive wear. In order to offset the increased wear as a result of higher injection pressures, three key factors must be addressed in order to maximise fuel system life.

Water, Abrasives and Supply Pressure


First, the fuel must be free of excess water, which breaks down the protective film strength of the fuel and leads to plunger scuffing and seizure failures.

Removing excess water becomes even more important as allowable fuel sulphur levels are reduced to near zero. The process to remove fuel sulphur also removes some of the long chain carbon molecules, which improve the film strength of the fuel. Very low sulphur fuel will also have lower film strength and lower natural resistance to scuffing and seizure


Second, the fuel must have microscopic abrasive particles removed to prevent injector abrasive wear. These abrasive particles lead to premature abrasive wearout of the injector cartridge valve, resulting in excessive high-pressure internal leakage. Many of these abrasive particles are present in the fuel as a result of the petroleum distillation process. Additional abrasives enter the fuel tank in the form of dusty air through unfiltered tank vents or unvented fuel caps.

Supply Pressure

Finally, fuel supply pressure to the injector must be maintained in order to achieve filling and proper operation of the injector.

*The above information is taken from
“Improving Fuel System Durability” by CATERPILLAR®

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