SHAFT AS 2244418 - Caterpillar

3406B Truck EnginesNozzle orifice erosion is abrasive wear at the orifice inlets in the nozzle tip. It can result in increased fuel delivery and black smoke for engines equipped with 7000 Series fuel nozzles. A recent study of nozzle wear and fuel sample analysis shows abrasive contamination in fuel is the predominant contributor to nozzle orifice erosion.
This conclusion is based on a large sample of field return nozzles selected randomly from all geographic locations in the United States and Canada. Returned nozzles were tested for functional performance and analyzed for conformance to factory specifications. In this study, all nozzles met current production specifications for tip hardness, and no deficiencies in material and workmanship were identified in nozzle tips.
Nozzle flow rates varied over a wide flow range independent of service miles. Some nozzle sets flowed significantly above specification at low mileage, while other sets showed only slight flow increases after high mileage. Nozzles within sets experienced similar flow rates, supporting a system related cause for nozzle flow change independent of individual nozzle variability. Abrasive contamination in fuel was the only feasible explanation for nozzle set, flow rate variation.
If used crankcase oil is mixed with diesel fuel, published guidelines should be strictly followed. See Engine Data Sheet LEKQ3255. But, even if these guidelines are met, small debris (5 microns or less) in high concentrations can still produce premature fuel system wear.
Nozzle orifice erosion and other fuel system wear can increase exhaust smoke. Excess fuel delivery, reduced atomization, changes to nozzle spray pattern, and injection pump wear can all contribute to excessive black smoke.
While nozzles with eroded tips can affect visible smoke, the degree it affects fuel economy may be largely driver controllable. As fuel flow increases, the majority of this fuel increase is converted to power under maximum load conditions. If vehicle horsepower demand is minimized through reduced; vehicle speed, aerodynamic drag, rolling resistance, etc., fuel mileage should not deteriorate even though the engine has additional reserve horsepower. In fact, additional reserve horsepower when used properly, can reduce shifting under certain conditions and potentially improve fuel economy.
Today's high performance fuel injection systems operate at higher injection pressures. Clean, high quality fuel, good fuel filters, and responsible maintenance practices are essential to long term fuel system reliability and performance.