DIESEL FUEL FILTER BASICS

INTRODUCTION

The primary purpose of a diesel fuel filter is to protect the fuel system components of the engine. A diesel fuel filter must be designed to remove extremely small particles to prevent the premature failure of these components. Many diesel fuel systems contain several fuel filters including a primary and secondary filter, as well as a fuel screen located at the fuel tank or transfer pump.

UNIT OF MEASUREMENT

The common unit of measurement in the fuel filtration industry is the micron or micrometer. One micron equals 40 millionths of an inch (0.00004"). A primary fuel filter must remove particles in the range of 10 to 15 microns (0.0004" to 0.0006"). A secondary or final fuel filter must remove particles ranging from 3 to 5 microns (0.00008" to 0.0001"). To illustrate how small these particles are, consider the following:

  • The naked eye cannot see particles smaller than 40 micrometers (0.0016").
  • A grain of salt is approximately 100 micrometers.
  • A human hair is approximately 70 micrometers in diameter.
  • A single grain of talcum powder is 10 micrometers.

FILTER PLUGING

Although diesel fuel filters are designed to remove damaging particles that find their way into diesel fuel, these particles are rarely found in sufficient volumes to plug filters. In reality, it is the fuel itself that plugs the filter.

ASPHALTENE PLUGING

All diesel fuel contains a substance known as asphaltene. Asphaltene particles are generally thought to be in the 1/2 to 2 micron range. While these particles do not harm the injection system, they tend to stick to the individual fibers of the filter as they pass through the filter. Over time, they coat the surface of the filter media and plug the filter.  A black, tarry substance accumulates on the dirty side of the filter element and prevents the passage of fuel.

DIESEL PARAFFIN (WAX) PLUGING

All diesel fuel contains wax. As the temperature of diesel fuel is reduced, wax crystals begin to precipitate out of solution. This temperature is known as the cloud point, the temperature at which the fuel transitions from a clear appearance to a cloudy appearance. The fuel filter begins to choke as more and more wax crystals begin settling out of solution and moving through the fuel system. A yellow, waxy substance eventually envelopes the filter and prevents the passage of fuel. 

CONCLUSION

There are normally several fuel filters found within a diesel fuel system. These filters prevent tiny particles from reaching the engine. Filters are susceptible to failure from asphaltene and wax. E-ZOIL manufactures several cold flow improvers that will keep wax crystals in solution to prevent fuel filter plugging. These products include DIESEL AID, DIESEL AID + CETANE, ARTIC POWER, and ARTIC FLO. These three products will depress the pour point and cold filter plugging point of diesel fuel and provide other benefits too.