Hi - first of all, I want to express gratitude for this forum - I went into being a diesel Benz owner with not a lot of car knowledge, and the amount I've learned within two months has been astounding.

Edited to add: The car in question is a 1983 300SD with 258k on it. I've owned it for about two months.

I've had an ongoing problem with my fuel tank since I got the car - it's filled with sludge, and I've had to change my pre-filters every four days, on average. It's getting on my nerves, to say the least. I started off running mostly biodiesel, but have added more diesel into the mix to thin it out, to the point where I'm now running mostly diesel. I bought the Startron diesel additive and threw in a bunch the first time, and am now adding an ounce with every fill up. I'm trying to keep my tank pretty full, and I had my mechanic change the fuel strainer and the main filter when he did some other work on my car. He said that he also cleaned out the lines.

We're both reaching the conclusion that the fuel tank needs a good cleaning - the price he quoted me for this made me swear to myself a little, so I'm hoping to do it on my own. However, I live in an apartment building and don't have shop space to do such a dirty job, so it's going to have to wait until my friend can kindly loan me space. In the mean time, I had a crazy idea...

The previous owner left a large auxillary fuel tank in the trunk - he was going to try to run SVO, but never finished installing the system. He also left behind the fuel lines that run to it, which are now just hanging out under the hood. There's a valve installed on the lines to divert the fuel flow from one side to the other. I am considering taking that tank out of the trunk, checking for a tank strainer on it, giving it the whole thing a good cleaning and putting it back. I'll install a pre-filter in the lines in between the tank and the main filter to be safe.

Is this workable as a short term (one month?) measure? Do I have to do anything to the inside of the auxilary tank after cleaning it? I'm not so worried about the long term health of the tank, more the short term health of my fuel system. And I've had to do small air purges after changing the pre-filter - I imagine that purging the air out after doing a tank swap is going to be a bear. Any advice on making that easier?

Thanks, all. If you think this is a bad idea, please feel free to tell me - I'll keep grumbling and changing my pre-filters until I can get the main tank clean.

There should be no problems using another tank for fuel assuming the tank is clean and free of holes and has a vent. Make sure there are both supply and return lines to the tank.

If I were planning on using it long term (a month or so) I would bypass the switching valves and run the lines right to the clear inline filter. Then hook up the return line to the return on the spin on filter.

Make sure the tank is secured in the trunk. Also make sure to use the hand primer to get all the air out of the lines. You may want to use a vacuum pump or 12V fuel pump to prime the lines to get fuel to the engine. Once you get the car running it should self prime out all the small air pockets via the return to the tank after a few trips.

Taking the diesel tank out to clean it is definitely the way to go.

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

Thanks - I got the secondary tank out and cleaned it, and am going to give it a few days to fully dry. The tank seems pretty solid and it does have a vent. It was pretty nasty in there, too - lots of the same junk that's been clogging my inline filter from the main tank.
I looked at the lines and it seems pretty easy to bypass the valve, so I'll definitely go that route. Good advice on the vacuum or 12V pump - that will certainly make it easier!

I'll get to do this all again in a month - so this will be good practice.

I use a homemade mini super sucker to prime lines/ filters..( used ac pump and grill tank)

__________________
1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.