Volume 6, Issue 10 (November 2009)
Addressing the Issue of Fuel Filter Fouling with Recent Changes in Fuel Quality
The recent introduction of biodiesel blends to the U.S. market has coincided with an increase in the reported problems of fouling of fuel filters and fuel injection equipment, manifested in power loss, noise, vibration, and increased filter changes. However, the introduction of biodiesel has to a large extent coincided with the introduction of ultra low sulfur diesel fuel and changes in engine technology, leading to higher fuel injection pressures. It is thus proposed that current incidences of fouling are not a problem brought about solely as a result of the introduction of biodiesel. A review of known fuel degradation mechanisms suggests that the effects of increased fuel pressure and also high shear environments should be examined as a probable cause of increasing deposit formation. Deposit formation on both fuel filters and injectors has previously been attributed to a variety of sources including: Biological contamination, both aerobic and non-aerobic, water contamination, adulteration with lubricating oil, fuel additive interactions, and biodiesel degradation. The deposits currently being encountered appear to be more akin to the high carbon content particles found in diesel exhaust than those previously described and are frequently found in the presence of deposit precursor molecules. This paper concentrates on the issue of fuel filter fouling, presents the analysis of currently encountered deposits, relates these results to some of the degradation mechanisms alluded to above, and suggests possible precursor molecules in fuels both pre and post stressing to support the proposed mechanisms. It is also shown that existing fuel quality tests do not correlate well with reported fouling propensity, suggesting that new test methods are required to ensure future fuels are fit for purpose.