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Thread: Bio Sludge in fuel tank

  1. #41
    Join Date
    Jan 2006
    In the sunshine state.

    Re: Bio Sludge in fuel tank

    This most lilkely is tar from old mineral fuel, not bug. Given the Pug 405 age it will have run on the dirty stuff and this is what drops out of it. When I first started on Bio I kept a sample of the fuel int he tank, guess what dropped out of it, tar, I have experienced bug too in the bio which is a lot worse than anything you are facing, Enjoy,
    Biodiesel Bandit

    Landcruiser '98 80 series B100.

  2. #42
    Join Date
    Oct 2011

    Re: Bio Sludge in fuel tank

    How does microbial sludge respond to caustic soda, compared to algal sludge?
    Doesn't algae need sunlight to form?
    I don't know whether it was "microbial" or "algal" - I don't know enough about microbiology to classify it. All I know is that it was biological in nature. There are thousands, possibly millions, of bacteria that can make thousands, possibly millions, types of biomass - some anaerobic, some aerobic, some autotrophic, some heterotrophic etc atc etc

    And as for its response to caustic, it's entirely empirical. If you spray oven cleaner onto the mould (biomass) in your shower, it will just lift off and can be wiped away. No idea what's happening at a molecular level

  3. #43
    Join Date
    Feb 2007
    Natone, Tasmania

    Re: Bio Sludge in fuel tank

    I bought 2 dead Mazda Capellas from a biodiesel guy; sitting 8 years. He had started out doing all the right things then stopped using a biocide. One car had to have the whole fuel system replaced, filled with bitumen and the case hardened parts were too corroded to use even when it was cleaned up. The other had a dead motor, no head, cylinders filled with rat piss and detritus but for fun I opened up the fuel pump and it was pristine so I swapped it and the fuel tank over. A diesel mechanic told me how to clean these things. They have to be stripped down. They use a bronze wire wheel and acetone on the steel parts which don't like water and an ultrasonic cleaner (with water) to clean the aluminium housings. You should not use caustic in your fuel system as it will react with aluminium. To clean the fuel system in situ and keep living organisms out of your bio use Chemtech diesel treatment just like was in car #2, a litre costs about $30 at Super Cheap Auto. Put 200 mls in each 200 litre drum of fuel and the bottle has a handy squeeze measure system and you won't have to get any on yourself. If your fuel has been properly washed and dried your troubles will be over.

    Although I was getting some black in my wife's PD Caddy van. It seems the individual injection pumps (one in each cylinder) are lubricated with engine oil and some leaks through into the fuel system.

  4. #44
    Join Date
    Mar 2013
    Sydney, NSW

    Re: Bio Sludge in fuel tank

    Evening all,

    I just cleaned out my sediment / water trap from my Rodeo again almost exactly 12 months since I did it last time:

    NOTE: my engine fuelling issues turned out to be nothing to do with this sludge - it was air leaks from what I can tell....and I'm still getting them, but that is another story.

    Unsurprisingly, 12 months later there was quite a bit of the sediment in there again that we labeled 'Tarry Substance' or TS previously.

    But this time it was slightly different - less tarry and more sediment-like...almost grainy like dirt, but you could crush it smooth by rubbing your fingers together.

    It cleaned up much more easily this time too - basically wiped out with a rag followed by a small spray of El Cheapo degreaser and it was clean.

    This may be a result of the fact that the cleaning interval was much shorter this time - only 12 months as opposed to about 4 years last time

    Since I did the original clean-out a year ago, I have been letting my finished fuel sit for as long as possible after reacting (4 - 6 weeks sometimes), draining glycerol off, then running my fish tank bubbler through it for a few days before washing - the latter always results in a bit more glycerol coming off even after sitting for a month. I have found I get a lot less soap and need to wash much less the before. Not sure if this has any bearing on the altered state of the TS.

    Photos aren't uploading for me again, so here is a link:

    2017 pics
    2018 pics

    I will try to send a sample to my friend the moss scientist and get him to look at it under a microscope.

    The good news is that the filter head and filter itself seem clean at the outlet, so I guess it as all doing its job. I dread the thought of that stuff building up in my IP.

    Question to other Mercedes drivers (and other vehicles that do not have water / sediment traps fitted): if running biofuels should we fit one?
    Last edited by 3DB; 26th February 2018 at 09:25 PM. Reason: added more content
    1995 Holden (Isuzu) Rodeo 2.8TD 4X4 - B100 since April 2013
    1976 Mercedes 300D Turbo 'The Coal Grenade' - B100 since May 2016
    (@thirddegreeburns on Instagram)


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