240D algae part 2

Over the last week or so, I’ve been dealing with the algae in the fuel tank of my 240D.    In the last update, after changing the fuel filters, I added the Penrite Diesel Biocide.   I was already noticing after about 30 kilometers the pre-filter was looking quite dirty and the car was down on power.

It seemed that some of the algae was able to get through the screen in the fuel tank.   As I still had two thirds of a tank of diesel, I figured it would make sense to try and get as much of the algae out as I could, before I changed the screen.   The screen is much more of a hassle to change than the two fuel filters.    Since the car was already down on power after 30km, I didn’t fancy changing filters by the side of the road, so I came up with another plan.

I purchased a cheap oil transfer pump on Temu, plus a bunch of cheap fuel filters.   My idea was to hook the pump up to the fuel tank supply and return lines in the engine bay, with one of those filters and see how much crap I could filter out before I changed the screen.

The cheap oil pump was self priming, which made it a doddle to install in the engine bay.    I wouldn’t consider doing this with a petrol car, but since diesel is not all that volatile, I felt ok doing it with diesel.

Starting the pump, I quickly got diesel running through the system and I could hear a lot of gurgling in the fuel tank.   I quickly noticed a couple of things.   Firstly, the pump volume was lower than I thought, and the filter was not getting dirty.

I am assuming the biocide has further blocked up the screen in the tank with dead algae and this is why the car was down on power.   I ran the pump for about 30 minutes, but the filter stayed pretty clean.

Next, to see how bad my algae is, I moved my setup to the rear of the car and put the inlet hose directly into the fuel tank.   This meant the pump was no longer going through the screen.   The amount of diesel going through the pump was a lot more, pointing to an even more blocked screen.   Surprisingly, the filter was hardly discoloured at all.   My theory is that the algae in the tank isn’t all that bad.   Bad enough to block the screen, but not bad enough that the tank is full of it.

At this point, the only thing left is to change the screen.   Since I had my pump setup, I pumped out 30 liters of diesel into jerry cans.   There is still plenty in there, so I’ll need to get another can before removing the screen.    The filter also allowed me to filter it before it goes into the jerry can, which makes me far more comfortable with putting it back into the tank after I replace the screen.

I tried again with my little remote camera, and I still wasn’t able to see much.   Just some minor spotting on the fuel tank walls, but it looked decent in there overall.