By David Sikorsky
Product Support Specialist
Caterpillar Forest Products
In my conversations with customers, I am often asked why methods of fuel system maintenance they have used for years—and perhaps still use successfully on some units in their fleet—are now unacceptable. I’d like to offer an explanation and guidance as we move forward in a “low emissions” working world.
Diesel fuel systems have undergone significant changes since the mid-1990s. These changes were first driven by a need to increase engine efficiency but now are primarily a result of emissions regulations. By design, injection pressures have increased 10-12 times over what was the norm in the ’90s. Common rail and mechanical unit injection systems used by various manufacturers currently operate at injection pressures approaching 30,000 PSI. These operating pressures require very close tolerances. To maintain them, fuel must be filtered continuously to a level of extreme cleanliness.
Adequate filtration for fuel systems of 15 years ago was provided by a water separator with a screen in it and a secondary filter that filtered particles down to 15 to 25 microns. Today’s fuel systems wouldn’t run for more than a few hours with that level of protection. Current engines require 10 micron primary filters and secondary filters in the 2 to 4 micron range. That issue makes fuel filtration as important to the performance and life of the engine as lubrication or air filtration.
To help ensure fuel system longevity, consider these steps:
First, change filters per the maintenance schedule provided by your engine/machine manufacturer. Second, be aware that virtually all brands of diesel engines manufactured in the last four to five years (all Tier 3 engines) are protected by sensors that will flash a code in your instrument panel for either water in the primary filter or a flow restriction in either of the filters. Often, the engine will de-rate as much as 33% as well. This is the engine’s management system demanding that you change the filter. This can occur prior to a scheduled filter change if you have filled up with poorly filtered fuel.
Installing a filtration system on your fuel delivery system will help prevent this situation. A 10-15 micron filter on your supply tank will go a long way toward extending filter life and protecting your fuel system. The quality of filters installed on your engine is of vital importance as well. You should always use the very same brand and part number filters that were installed by the OEM when the engine was built. That way you ensure both a level of quality that was designed for your engine and limit your liability (warranty repairs).
To install a set of unit injectors and an injection pump on a Tier 3 engine of, say, 175 HP, will cost more than $3,000 in parts and as much as $1,200-$1,500 in labor. Because of the complexity of these engines, this type of repair almost surely will need to be performed by a dealer tech. This should be motivation enough to avoid an attempt at saving a few bucks on “will fit” filters. Finally, it is important to understand the proper way to change fuel filters on today’s engines. The old way of filling the filters before spinning them on with your empty oil jug or tank nozzle simply is not acceptable.
If you use that method, the fuel you just poured into the filter is the first to go through the pump and injectors. Absolutely unfiltered, it can, and will, damage them and shorten their life. Filters on most Tier 3 engines must be installed dry and filled with the primer pump. (One exception is an OEM that uses a special filler that screws in the top of the filter, directing fuel through the element.) In this manner all fuel is pumped through the filters and filtered to the required level of cleanliness, providing optimum fuel system life and engine performance.