Fuel System


Fuel Filters
Fuel Polishing – Methods
Fuel Polishing – Need For
  • Very simple matter to measure the quantity of fuel returned to the tank. Just break into the return line to the tank and catch a known quantity of fuel in a known time and compute the flow rate. You can do this at the dock with the engine in neutral. Place a bucket under the return line and have a large zip-lock ready to catch the measured fuel. Have the engine started and increased the RPM to cruising speed. Then catch fuel in the zip-lock for a timed interval. The longer the timing interval the more accurate the results will be.  (http://www.trawlersandtrawlering.com/howto/captnwil.html)
  • It is generally agreed that water in the fuel tank causes all sorts of hell. The experts tell us that algae is born, lives, multiplies, and dies in the surface between the water and diesel fuel. These critters and their residue are a major source of trouble. The moral is: no water, no algae. Most of the water gets into our tanks by water condensing on the inside surface of the fuel tank and less often on the surface of the diesel fuel itself. This occurs every time the temperature of a surface is below the dew point temperature of the air to which it is exposed. Without getting too technical, more moist air will have a higher dew point temperature than less moist air and be more likely to cause condensation. It is also helpful to note that the condensation always occurs on the warm side of the surface  (http://www.trawlersandtrawlering.com/howto/captnwil.html)
  • The most common means to prevent condensation in fuel tanks is to keep the tanks full. If they are full, there is no air in them so no condensation can occur. It is especially important to keep the tanks full when the boat is idle for a period of time.  (http://www.trawlersandtrawlering.com/howto/captnwil.html)
  • Desiccant filters in the vent lines have tremendous possibilities. If they can be fitted properly, they will keep most of the moisture in the air from entering the fuel tank, which will lower the dew point of the air to very low levels.  (http://www.trawlersandtrawlering.com/howto/captnwil.html)
  • It is one thing to get such dirt into a 20-gallon fuel tank and quite another to get it into a 300 or 400-gallon fuel tank on a trawler. The complete fuel turnover rate in the 20-gallon tank guarantees that the entire contents of the tank will be kept stirred up and the crud will quickly end up in our fuel filter. In the 400-gallon, on the other hand, the dirt will just settle to the bottom of the tank like the silt in the delta of a river. It will build there over time so that it can cause its worst evil at our most critical moment.  (http://www.trawlersandtrawlering.com/howto/captnwil.html)
  • Then there’s that black stuff that begins by discoloring the fuel filter, then discolors the fuel, then makes the fuel black and puts jelly-like stuff on the fuel filter, and then just shuts down the whole fuel system…I suspect it is the result of the solids from the original crude oil settling out and returning to their natural state. No matter what the cause, it is an ever-present, ever-continuing condition that adds to that awful mix at the bottom of our tanks. Let diesel fuel stand long enough and it will turn black.  (http://www.trawlersandtrawlering.com/howto/captnwil.html)
  • The common system with one secondary and one primary fuel filter tries to keep the fuel that enters the injection pump just like new and the only effect on the remaining fuel is the returned clean fuel. Once we understand that most of our engines return very little fuel to the tank it becomes obvious that this system has little or no effect on the fuel in our tank. The fuel in the tank keeps getting less and less just like new, and filter replacement intervals decrease.  (http://www.trawlersandtrawlering.com/howto/captnwil.html)
  • diesel fungus that was treated with a biocide. One of the most common is C. Resinae. The biocides tend to kill off the fungi or bacteria and then leave that residue behind which can plug a filter…the residue that gets on tank walls, and hides behind baffles, needs to be scrubbed clean or be given a chemical bath. I would strongly advise against the use of chains in tanks as even a small piece of dissimilar metal in the bottom of an aluminum tank can wreak havoc galvanically.  (http://www.capedory.org/board/)
  • There is, native to this planet, a life-form that thrives in diesel fuel. It’s commonly found in most tanks that aren’t really, really new. Ideally a biocide for treating diesel in a tank would kill and DISSOLVE the little critters. To my knowledge, none of them do…, so you just swap one problem for another. You have dead stuff that you must filter out, instead of live stuff that you must filter out.   (http://www.capedory.org/board/)
  • Upon inspection, when opening the top of the Racor filter, we saw there was not enough fuel in there… obviously, something went wrong along the fuel lines. Clogged, or crud from the tank, etc. A couple of days later, I cleaned up Racor as well as I could, replaced the filter which was absolutely full of junk, filled it up with new fuel. I also replaced the secondary fuel filter, cleaned the electric fuel pump. Then bled the system. My engine started again fine. However, since I have owned the boat-12 yrs. now, I have never cleaned that fuel tank… neither the PO. So I can only imagine what can be in there. I did not want to start my engine again without trying to do something about the fuel in that tank and trying to somehow clean it, if possible…Most of the water present in fuels will drop out as it is heavier than the fuel and will sink to the bottom if given time.  (http://www.capedory.org/board/)
  • Water gets into diesel fuel storage and vehicle tanks in several ways – by condensation of humid air, during transportation from refineries to service stations, by leakage through faulty fill pipes or vents and by careless handling. Water can cause injector nozzle and pump corrosion, microorganism growth and fuel filter plugging with materials resulting from the corrosion or microbial growth. Both vehicle and storage tanks should be checked frequently for water and drained or pumped out as necessary. In extreme cases, biocides may be required to control microorganism growth. In cold northern winters, ice formation in fuels containing water creates severe fuel line and filter plugging problems. Regularly removing the water is the most effective means of preventing this problem; however, small quantities of alcohol may be used on an emergency basis to prevent fuel line and filter freeze-ups. Cleanliness refers to the absence of water and particulate contamination. This characteristic is important because dirt and water can plug fuel filters in your engine and cause severe damage to your fuel injection system because of the close tolerances within fuel pumps and injectors. All diesel engine manufacturers equip their engines with fuel filters to protect the fuel delivery system. You should replace these filters according to the manufacturer’s recommendations. Some manufacturers also provide filters with drain valves and recommend periodic draining of any water that may accumulate from condensation and careless handling in storage or vehicle tanks.  (http://www.cleanfuelguys.com/heat.html)
  • Water in tanks can freeze 20F – 30F above the temperature at which fuel-related problems begin (cloud point). Ice crystals can build up on filters, restricting flow and compromising performance. They can also restrict fuel flow in tank pumping lines…In warmer weather, the presence of water in tanks may encourage the growth of fungi or bacteria which live in the tank water bottoms and feed on the fuel. Under the power of a microscope, these bugs look like deep-sea creatures. To the naked eye, these bugs show up as slimy mats of substance that can be any color from green to black. Under ideal conditions, these bacteria can double in number in as little as four hours. When left unchecked, they can be drawn out through suction lines and plug filters. In addition, the by-products of their fuel consumption are very acidic and can cause pitting and decay in tank bottoms. Many tanks go unchecked for years, accumulating water from any number of sources.  (http://www.cleanfuelguys.com/heat.html)
  • I think its a good idea to be able to have easy access to available fuel i.e.: you can easily pump it out to pre fill a filter or if someone is in need of fuel. Everyone I have talked to who have had to polish their fuel have had older boats (tanks) several owners, several levels of maintenance skills and a lot of crappy fuel from somewhere. So there is a lot of build up in those olds tanks. rough conditions stir it up and your filter is shot.I would carry a screen (Baja) to filter the fuel going into the tank if in doubt. And use the simplest way you can think of to be able to polish the fuel via an independent internal system while possibly still running the engine from the same tank.You will probably have a brand new or very cleaned out fuel tank to start with so you are way ahead already. I would check out the fuel treatment stuff if fuel sits for very long. (Ben Thomas, Beta Dealer)

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