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Diesel fuel contains varying degrees of entrained air in the form of foam on the surface or suspended in the bulk fluid as tiny bubbles. Additionally, fuel is driven into the fuel pump by atmospheric pressure, which is usually only enough pressure flow to fill the pump at idle speeds. Consequently, at higher operating RPM’s, the stock pump cavitates producing vapor.
Air and vapor are compressible. The presence of air/vapor in the fuel injector delays the pressure build-up. |
This delays the injection, resulting in Retarded Injection Timing.
Retarded injection timing in a diesel, just like bad spark plugs in a gasoline engine, causes lost power, poor fuel mileage, and an increase in exhaust emissions. Retarded Injection Timing caused by air/vapor is the primary source of the rough idle, lost power, increased fuel consumption and excessive exhaust emissions of the diesel engine. |
Air/vapor in the injector can also cause permanent damage in the form of galling and pitting of the barrel/plunger assembly and tip erosion.
The conventional vacuum feed fuel supply system does nothing to remove entrained air from the fuel. In fact, it only makes things worse. As the filter plugs with use, the already inadequate fuel flow to the engine is further reduced, increasing cavitation and retarding injection timing even more. |
