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Old 15-06-2010, 17:17   #1
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Diesel Fuel Contamination

Wondering what experience anyone has had with diesel fuel that has been blocking up filters because of fungus growth, or suggestions on prevention. I have copied below from a BP web site describing preventative measures.
Should a tank become over infested with fungus then filters will start blocking with a black slimy deposit and the fuel may be hazy with water and dirt suspended in it. In such cases the biocide should be added to the fuel tank and then the fuel in the tank should be circulated to ensure that the biocide spreads throughout the fuel. The biocide should be one which will kill the fungus and then assist the water to drop out of the fuel. Fueltreat BC 250 will do this. Following treatment, the water and dead fungus will drop to the bottom of the tank. It should then be drained off or sucked out with a hose, otherwise it will
sit on the bottom until becoming stirred up in rough water and again block filters. Treatment should continue for a few loads until filter operation has returned to normal. In an extreme case it may be necessary to empty and enter the tanks to carry out manual cleaning.
The cost of treating will depend on the biocide but can be estimated at about 1 to 3 cents per litre depending on the treat rate.
For further information, please call the
BP Lubricants and Fuels Technical Helpline
1800 033 558
or visit BP Australia - Products and services - On the road - Fuels - Fuel news
Regards Peter

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Old 15-06-2010, 17:26   #2
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HAd this happen a couple of times....Drained all the fuel replaced with new, scrubbed the tanks and added a fuel treatment for it.. Also if you are not using your boat too much fill up the tanks all the way. I use Biocide all the time now unless i'm going to be sailing a lot and using the engines as well. The biocide has prevented it happening again!

I pre filter everything that goes into the tanks no matter what...amazing the crap that comes out of the pumps sometimes.

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Old 15-06-2010, 19:18   #3
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It is an age old problem for as long as there have been marine diesels. It happens even in big ships as was demonstrated by the engineering problems experienced aboard the Admiral Graf Spee on her cruise from August to December 1939. As sailingaway states, use a biocide and multiple filters--mesh or cartridge types to remove the bio-contamination and centrifugal filters to remove water and particulates; filtered fuel can then go into a day tank to supply the engine, heaters, stove, and whatever else you have that runs on diesel. This will make it much easier on the engine mounted filters which will not have to work so hard or be changed so often.
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Old 15-06-2010, 21:44   #4
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Large dual Racor filters when if and when you get this are a big help.

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Old 17-06-2010, 08:45   #5
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Use some SEA FOAM you can buy it at auto parts and marine stores. a guy at my marina had a problem with his filters getting clogged so he put some seafoam in the tanks and it was no longer a problem.
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Old 17-06-2010, 09:35   #6
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Originally Posted by David M View Post
Large dual Racor filters when if and when you get this are a big help.
Also, a fuel polishing system can really, really help.

Fair Winds,
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Old 18-06-2010, 05:59   #7

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I have this problem with my starboard fuel tank. It's not horrible, yet filter changes are necessary more often than they should be. I've tried the chemical route yet the nasty slime persists. In my case I think the next step is removing the tank and thoroughly cleaning it.
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Old 13-03-2013, 10:11   #8
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Re: Diesel Fuel Contamination

I had bought an old 38' diesel rv 10 yr ago and the filters kept getting blocked every 500 miles from a rusty tank. I added a Gulf Coast paper towel filter as an inline filter before the other 2 factory installed filters and have had no problem since. For 10 years I have to move the rv one mile down the street every 7 months for 3 days because where I live out of it, the rv park has rules to do so. Same tank of fuel for all 10 years, which I once added fuel conditioner to years ago. It starts up with in 1 second every time from sitting 7 months straight. Those filters are suppose to filter out all containment including biological growth. In fact some people have bought bad contaminated fuel with algae and water for cheap and then use the Gulf coast filters to clean it all out. Each roll of bounty will absorb 2 quarts of water and 2 pounds of containment I think.

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