How to Put Together a Homegrown Fuel Filtering System
Keeping your diesel fuel clean should be one of your highest priorities, and you can avoid a lot of trouble by adding extra filtration. During the 2015-16 winter aboard Eclipse, our Tayana Vancouver 42, we pulled out our old Perkins 4-108 for a rebuild. With the engine out of the way, I also took the opportunity to plan and install an electric pump-driven polishing system that would improve the likelihood of having clean fuel in our two tanks.
In this context, the term “polishing” really just refers to the repetitive refinement of the diesel fuel by circulating it through an external filter. The system I decided on also offers some bonus features, like the ability to move fuel between Eclipse’s two tanks and the option to keep fuel flowing should the primary filter experience a blockage. Its electric pump also makes an easy task of priming the fuel system all the way to the injectors.
It only took a brief look at some of the commercially available polishing systems to determine that a homegrown approach would be much more cost-effective than spending upward of $3,000. It’s important to note that systems at this price point are slightly more complex than the dual filter setups more commonly found aboard many sailboats. Redundant filters are usually designed so that there is always a clean filter ready to go when the other clogs up. The operator then has to just turn the lever on a valve to swap over to the opposite filter. This, in turn, should keep the engine running while changing out the clogged element (not an easy task in a big swell, next to a hot engine). That said, it was my hope that my DIY polishing system would reduce, if not eliminate, the need for this kind of an emergency filter change in the future.
Essentially, the system consists of two filter housings, two manifolds, and various bits of hose, ball valves, low-pressure check valves and threaded pipe connections. All parts were purchased from McMaster Carr, Ebay or Amazon. I used a USCG approved A1 fuel hose from Trident along with proper non-perforated 316 stainless hose clamps. Every connection was also double clamped, and all threaded connections were sealed with liquid Teflon plumbing sealant that is rated for diesel fuel. Finally, I used stainless nipples between any aluminum and brass connections to minimize galvanic corrosion. Everything was secured to a large piece of Starboard that required some creativity to mount in the engine compartment.
The most important component of this system is the polishing filter—this is where the magic happens—and I used an industrial-style depth filter from Shelco. The specific model I have is an FLD-78, in stainless steel, purchased on Ebay for about $100. These are the same types of filters that can be used under your sink at home with tap water, which means they are meant for a high volume of flow and can trap enormous amounts of particulate matter compared to a surface filter like those found in many standard water separators. Their thick fiber elements look like a roll of toilet paper and are inexpensive compared to their surface-filtering counterparts. (Depending on the size of the housing you can find filter elements for less than $6 each, far less if you buy them by the case.) Just be sure to buy the type that is compatible with diesel fuel. I chose a 10 micron filter, which is sufficient for most conventional diesel engines. If you have a modern engine with common-rail fuel injection, you’re going to want to filter to 4 microns or smaller.
Like most projects, most of my time was spent researching and planning. Full assembly probably took about 20 hours, but that was after a number of late nights on the computer doing research and putting my shopping list together. The system is not perfect. It cannot cleanse a huge load of bad fuel, nor can it clean thick sludge from the bottom of a badly contaminated tank. However, it is a great tool for preventing good fuel from going bad.
Phil Gutowski sails a Tayana Vancouver 42 and lives aboard in Boston, Massachusetts
Photos by Phil Gutowski