Plugged Fuel Filters and Cannot Solve the Problem?

It is not algae sludge. What is it?

Here is one that had a lot of people fooled for a long time.

Relatively clear fuel but plugged filters after 2,000 mile in a Class 8 Truck

In this case the problem was constant filter plugging with a black colored material.
Generally if it is a fuel tank with a black film plugging filters we assume it is bacteria so we recommend Technol 246 tank cleaning additive.

Technol was used as direct for 30 days and the problem did not go away.
At that point we asked for photos.

The fuel was relativity clear but filters were plugged with the mystery black material.
The filter and fuel sample were sent to a lab for answers. No bacteria was found but was what the black material? We again gave our best guess, could it be rubber. Some fuel blends with high amounts of biodiesel are not so friendly with some rubber hoses. The fuel eats up the hose from the inside out and causes a similar black substance that plugs filters.

Again back we go to the lab to identify the culprit.

The tank was drained and pressure washed and this residue was found in the wash water. It was send to a lab for identification.

No it’s not rubber it is soot from the engine. The engine has 5 of 6 bad fuel injector seals and this was sending engine soot back down the return line to the fuel tank. So as we cleaned the fuel and the tanks, the engine was creating the problem as the engine was running.

To self test filter plugging mysteries take a sample of the sludge and mix it with as small amount of Xylene. Xylene is as synthetic paint thinner available at the hardware store. This should dissolve any biomass sludge if the problem is bacteria. If it does not, rinse in warm soapy water and rub the material between your fingers. Feel gritty? Could be soot or does it feel like rubber?