I was polkaing around the internet and found this article which I will summarize: The article focuses on contamination of diesel fuel in the fuel tank (in this case a 600 gal diesel fuel tank on his boat) and Cptn wils idea as to the cause/s and his solution. What I got from the article is that he believes that part of the fuel contamination problem is due to the fuel in the tank being unfiltered and not being circulated. In short the crud is allowed to build up in your tank until it starts to come out of the tank and plug up your fuel filter eventually shutting you down. At this point the feels you are stuck with a really difficult problem. Chemical solutions to kill the algae and result in more plugged filters due to the “dead bodies“ (and gives an example of the chemical solution causing problems with injectors on a Detroit Diesel engine). After physically cleaning out the tank the problem reoccurred several years later and he wanted a more permanent solution.

His idea was to install a separate fuel pump and separate fuel filter/water separator system to filter the fuel from the thank and return it back to the tank.
Why Mercedes owners might be interested: I was thinking mainly of people who use alternate fuels in their Mercedes and keep a bunch of those plastic (primary) fuel filters (and gloves) in the glove compartment because occasionally have to pull off of the road to change them.

It would not be too hard or expensive to hook up an electric fuel pump to a remote 2 micron fuel filter/water separator to filter the fuel in the tank and return it to the tank.
Here is the article: http://www.trawlersandtrawlering.com/howto/captnwil.html

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84 300D, 82 Volvo 244Gl Diesel

The Mercedes fuel injection system already does that through the filter and fuel return lines.

If you want to filter more, change the plastic secondary filter out for a Racor 500FG or better.

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Gone to the dark side

- Jeff

Not being a boat owner it was new to me (and may be new to others also). What I got from the article was that by having the separate fuel filter system it helped prevent having your normal filter system get plugged up an some awkward time and shutting you down (or at least happening as often) and I can see the benefit of what he is saying if I was having fuel quality issues.

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84 300D, 82 Volvo 244Gl Diesel

People will have to answer that for themselves. I would not want to have an unexpected filter change a filter on the roadside on some cold winter minus degree /rainy/sleeting day and I sure would not want to be on a boat in a storm (when I need to mantain control of the boat) having to change a fuel filter.
Cost:Electric fuel pump $30-40, filter setup (depends on what you want, could be around $40 for a filter base and what ever a spin on filter cost), hose say $1 a foot and 2 Ts. One T tees into the fuel line before it goes into the primary filter the other tees into your noremal ruel return line. I think it could be done for $100 or less.
Added: If the secondary filte also was plugged the road side change gets a little more complicated as some folks have trouble bleeding their system of air.
http://www.peachparts.com/shopforum/showthread.php?p=1786228&posted=1#post1786228

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84 300D, 82 Volvo 244Gl Diesel

You won't have an unexpected roadside filter change if you change the filters at least at every other oil change and buy your fuel from a clean, reputable station.

i agree

anybody that has an "unexpected" fuel filter clog is just unprepared and hasn't given the engine proper maintenance in the first place.

Consider not only the cost but the labor involved as well. And somebody mentioned also that the Benz diesel basically does filter out fuel and returns it to the tank (excess fuel that gets "pumped" but not "burned"). I understand it doesn't filter high quantities but it's surely helpful.

I guess it's a good thought though.

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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me
1983 300sd
1985 500sel
1992 300se

While I did mention Mercedes remember this part of the forum the Diesel Forum and I notice a lot of the members have other diesel vehicles.
What I got from the article was that by having the separate fuel filter system it helped prevent having your normal filter system get plugged up an some awkward time (or at least happening as often) and I can see the benefit of that.
Years ago when I worked in a fuel injection shop and we installed the Racor or Dhal filters (mostly on Chev 6.5 and Ford 6.9 PU trucks) it was not unusual for our customers to complain that within a day or two they were stopped dead on the road. The filters had done there job but plugged up and cut the fuel off (they had contaminated fuel in their tanks). You can drain the water out of the filter but the algae and rust stay on the filter element. (Not to mention the cost of the Racor filters.)
What I got from the article is that this was a way to deal with/reduce the specific problem of contamination in the tank before it gets to your normal fuel system and you get shutdown.

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84 300D, 82 Volvo 244Gl Diesel

no benefit to us since we only have 23 gallons of fuel which most of us burn through in 1-2 weeks( 2 weeks for me)

I have to admit, running diesels for decades and being used to big Racor filters, I'm always uneasy about driving a distance and having to buy fuel somewhere unfamiliar. I did have an algae problem once, in a coach, and it was a pain to change filters constantly until the contaminated fuel was used, more to it than that, but at least I had an electric prime pump that would prime before cranking the engine (plus a diesel genset to keep batteries up if necessary).
I carry two each primary and secondary filters, cheap and easy, and the tools to change them. Also a quart of ATF to prime the filter, and a good booster box to help crank if it doesn't prime right away, that's the downside of the 60x is no hand pump.

Anyway, if I were to make a modification in the filtration, I would do it like most diesel boats: I would eliminate the difficult to change cartridge primary filter from the car, and replace it with a dual-racor setup like a pair of heated 500FGs with water warning, and a RACOR vacuum/pressure gauge to show restriction and indicate a clogging filter.
The idea is that you run (the boat) on one filter, if there is a problem (at sea) you go into the engine room and throw the valve to run on the other filter. You can even change the filters while the engine is running, kind of un-necesary on the benz, but I thought I'd throw it in there. Probably an electric boost pump would be nice, I would always change the Racor filter element (lid comes off, load/unload through the top with fuel still in the filter) and then start the boost pump, when fuel starts bubbling out around the T-handle I'd snug it down, primed and finished. Can do that with the engine(s) running.

Anyway, I wouldn't bother with a polishing loop, but the dual heated racor replacing the M-B primary / spin-on filter would be a tasty change, ... if I had the space.

Actually I have a spare 1000FG I was going to use for the genset, ... wonder if I really need a windshield-washer bottle in the car?

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Gone to the dark side

- Jeff

When I first got my 87 300D I had trouble with plugging filters. One of the things I did to help was to connect the suction of my external fuel pump/filter to the supply line from the tank and put the discharge back into the fuel tank. I ran it like that for about an hour. I think it helped. Who knows.

-Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.