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Contaminated Diesel Fuel Cure

Has anyone successfully rid their fuel system of algae? What is the best method? When I did my annual fuel filter change, I found that the Racor filter had quite a bit of black stringy and black globular material in it. I am presuming that this is algae and that I received a contaminated fill up this summer.

What to do now. One mechanic assures me the algae will die in the freezing winter temperatures of Western NY and will slowly be captured by the filter next season as long as I monitor and frequently change them @ $17.95 a Racor filter. Another mechanic says to pump the diesel from the tank, rinse well and discard it via a waste management company (total cost about $90 plus the cost of refilling the tank). Has anyone successfully rid their fuel system of algae? What is the best method?
Paul Law, Avalon #912

  • By any chance does your fuel system have the screen on the fuel tank line pickup and have you removed the screen? By the way, the cost of cleaning the tank is still a lot less expensive than rebuilding, and replacing, the injector pump. Rich Dwyer "Rebellious"

  1. Have you been treating your fuel with biocide regularly at every fill up? If not, you could have been growing the algae all by yourself and it may not have been the fuel vendor's fault.
  2. It is possible to have the fuel analyzed to determine what the growth is?
  3. It is also possible to have the fuel "polished" or reconsitituted, rather than discarding it? Depends on how much fuel you have left in your tank.
  4. Have you checked the strainer on your fuel pump also?
Stu Jackson #224 "Aquavite" San Francisco

  • We've had a problem with our 1986 boat with algae. The first year we bought the boat (1996) the engine quit several times until I removed the pick up tube on the fuel line. Thereafter, we had the engine quit once or twice after traveling in heavy seas (wash machine action in the tank) after not changing the filter for some time. For the past two years, I've changed the filter regularly at approximately 50 hours or after numerous heavy seas travels and have ("knock on wood") not had the engine quit. My neighbor had the tank cleaned on his 36 with the high pressure filtering system. The residue in the Racor filter from his boat looks worse than ours. Think about it, the tank has baffles and corners. How do you think the high pressure filter system can "see" all of the blind corners and sides around the baffles from that small fuel hose entry hole? My solution is to keep a clean filter with regular changes and regularly use a biocide in the tank (one a month). After seeing the residue from my neighbor’s boat, I believe the $250 cost to hire one of the high pressure filter services is a joke. That buys a lot of Racor filters (about 14) which would bring you to a break even at about four years. By then your filtered tank will have another severe algae problem. Anyone who believes that their diesel fuel tank is algae free will eventually get a shocking surprise when the engine shuts down in the most awkward spot after some heavy sea traveling. By the way, I also investigated replacing the tank. You can replace the tank for the same amount of money as getting it washed down. Removal / replacement looks fairly easy. Disposal of your old tank could be a problem, but then if you could take it home, dry it out and clean it over a period of a two to three years, it could be your next replacement when your new tank gets algae in it. Frank "Kik N Bak"

  • We had a similar problem with our C-30 last summer which stopped the engine a couple of times. After two filter changes and a good dose of algaecide in the tank, things appeared to be OK with the filter fairly clean at the end of the season. However, the problem was back early this season with the filter so gummed up it was hard to imagine why the engine ran at all before it quit. The boat is in Bayfield on Lake Superior with -30 degree temps common in the winter. The little bugs apparently came through that without suffering any loss of vitality, so I wouldn't count on freezing to kill them off. They can't exist in diesel fuel or water alone, but thrive at the interface between water and fuel. Thus if a water-fuel interface exists in the tank, they have a great habitat. Early this summer, we had the tank professionally cleaned (in the boat) and fuel "polished." This consisted of pumping it through a multiple filter arrangement, stored in a dockside tank, algaecide added, then put back into the boat tank after the tank had been cleaned and sterilized. Cost was around $130. There have been no problems since and the filter has remained clean. Based on this experience, I would suggest the second of your two options. Make sure no water remains in the tank as that's what provides a suitable environment for the little critters to prosper. Jim Moe "Windseeker" #976

  • I've had more up-close and personal interaction with the fuel tank for my 1988 Catalina over the past two years than I'd have preferred. Bottom line is that I agree with one of the prior posts about regular use of biocide and that the onboard fuel and tank cleansing operations are not work the money.
Summer 98 I noticed a diesel smell in the aft cabin. Upon investigating (which required exposing the tank by removing the port side wooden "wall" in the aft cabin) I found that the tank was leaking from somewhere on the bottom. After draining and removing the tank, it appears that the tank was sitting directly on the fiberglass shelf as it was supposed to, but that over the years, water had leaked down onto the shelf and had caused a couple of pinholes in the tank. This was easily remedied by a local welder who cut out the offending areas and welded new surfaces on the tank. Also did a complete cleansing of the tank before sealing it up. Changed the hoses when re-installing the tank and placed some of the plastic cockpit flooring squares under the tank to minimize exposure to water (also tightened up all of the deck fasteners). All in all a couple of hours of labor and a slightly twisted back from maneuvering the tank out of the aft cabin area. No problems for about a year.
July 99 - got a bad batch of fuel over the weekend of the 4th. Engine ran fine for about 4 hours after filling up but then the filter clogged and was not able to get it running so had to take a tow back to the dock. Turned out that not only was the intake filter clogged but the filter on the return line was as well. Plus the pump (which was going on 8 years anyway) died. Changed both filters and the pump and had the fuel tank "power filtered" by a local fuel cleansing company, which for $225 included a shock treatment of biocide (which costs about $10 at the local supply store). Everything worked well for about 2 hours of engine time.
August 99 - Two weeks later, had the primary filter completely clog up. The fuel was very cloudy and had a fair amount of precipitate. Changed the filters again (I'm thinking of buying stock in Racor), and drained the tank and disposed of the fuel at the local municipal hazmat recycle station (luckily no charge). Cycled a couple of gallons of clean fuel in to try to mix the sludge up a little, and did a little brushing through the fuel gauge access hole. Not very robust by any means but the fuel runs clean at this point.
So, many fuel filters and a pump later, I think I'm back on track. Lessons? Nothing earth-shattering. Biocide at all times. Carry spare filters and a pump. Wouldn't waste the money on the fuel cleansing process. Remove and clean the tank every couple of years. Change the primary and return filters every 50 hours, even if the bowl looks clean. J Murray "Therapy" #564

  • I don't know about "best" method, but here's my story: I think the fuel in my tank was contaminated when I bought the boat. It had fuel problems at the survey, and the broker had a mechanic "fix" it by a method that I would (with hindsight) describe as "covering up the problem". He moved the fuel pump ahead of the Racor filter, so it was blowing through the filter instead of sucking. For winter storage, I did put in fuel treatment and another 5 gallons or so to top up the tank. It always ran a little rough, but was at least working until one day I was motoring along in a bit of chop and the engine stalled. Ok, so it's a sail boat - we can still get home, right?
I had a mechanic come out and change all the filters, which helped for a day or two. Then it got clogged up again, and the idle speed dropped too low to sustain the engine. I considered having the fuel polished, but I had really had enough of engine problems. I took it to have the tank steam cleaned. To steam clean the tank, they empty it out and blow superheated steam through it. The heat of the steam helps to melt any semi-solid gunk that may be there. This, plus the force of the steam, gets it a lot cleaner than just sucking the fuel out through the filler hole. The place that did the work normally polishes the fuel and puts it back in the tank when you're done, because that is cheaper than disposing of the contaminated fuel (which is a hazardous waste). When I picked up the boat, he told me that it was so bad that they discarded about 10 gallons (i.e. more than half a tank) of fuel because they couldn't get it to run through their filters.
Because I have had such a bad time with fuel contamination (and because I know what they eventually found in the tank), I'm glad I had it steam cleaned instead of just pumped out and filtered. It was pretty expensive, though, at over $400. I guess I could have replaced the fuel tank myself for that much, but then what am I going to do with 10 gallons of liquid hazardous waste and the old fuel tank?
I had a lot of problems with water and algae in the fuel system about two years ago until I replaced the standard plastic fuel filler deck fittings with good quality stainless steel fittings. Basically the problem was that the plastic screw in caps fractured at the bottom. While trying to sort out the problem I had the fuel tank professionally "polished" twice at considerable cost.
I wouldn't have the fuel polished again. It’s much cheaper to use a biocide routinely and, if necessary, either run the standard electric fuel pump with the engine bleed bypass open or buy a fuel pump and spare fuel filter and make up ones own fuel cleaning circuit. As an aside I discovered that the manual pump on the Racor contains components that corrode on exposure to water (at one point I had a lot of water in the fuel). The manual pump is to prime the filter and is located in the top of the unit. I managed to clean up the corroded parts so saving the cost of replacing the whole Racor unit but not everyone would find it practical or worthwhile. The message: check the filter every day and drain it if there's water or a sudden increase in sludge. Beware of water in the fuel, in rough seas the agitation can cause the water to emulsify in the fuel. If that happens the engine probably won't run. Although the electric fuel pump is after the Racor filter you should beware of plugging of its internal filter. During the same period when I was getting water into the fuel system, I also found the engine wouldn't put out its full power. The cause was fuel starvation due to plugging of the fuel pump filter. The standard pump can be dismantled without disconnecting the hoses by twisting the bottom cover of the pump. It has a bayonet style attachment. BUT beware there is a spring and several small components that are easily lost into the bilge. I know, I've lost them and had to buy a new pump. Charles Holder

  • There has been much talk on the problems of buying contaminated diesel. I would ask you to consider the following. When you pump fuel into the tank you are stirring up whatever crud, algae, bacteria and sundry goo is already lying on the bottom of the tank. Heavy seas also stir up the evils within. Algae and biocides leave the little bodies dead but intact within the tank. They have to go somewhere. The water removing additives somehow encapsulate the molecules so they mix with the fuel. I find most of my goo in the strainer in the fuel pump, which is before(?) the primary filter on my boat. So much so that I keep two extras of these on hand at all time, as well as spare primary (Racor 2micron) and secondary fuel filters. One idea you may consider is to get a yellow plastic five gallon jerry can and purchase Diesel from a truck stop - where daily consumption is great and the fuel doesn't sit around collecting wax and flora, (and costs 30% less than at a marina). Take it to the boat and pour it through a water-separating funnel (available at auto supply stores) to pre-filter the larger lumps. I would do this, but my marina forbids transferring fuel at the slips. There may even be state or federal laws against this. Good thing I and all Catalina owners are law abiding citizens. Charlie Pearsall

  • My '86 C-30 had the fuel filters arranged as you describe here. On advice of folks on one or more of these lists, who advised me that the newer Catalina's had the filters set up so that the fuel goes through the primary (Racor) first, then the fuel pump, and then the secondary (spin-on), I recently rearranged mine. So far, works fine, and avoids the problem of the fuel pump clogging. Just took some fuel hose and a few minutes' time. Changing the filter in the Racor is a different matter. That is a chore. John D. Watson, Birmingham, AL