Fouling or growth of microbes on filters can cause severe problems. The above image shows an example of a diesel filter with less than optimal function, due to fouling from microorganisms. A common cause of these problems is presence of water in the fuel, for example from condensation of water in the air, and the problems typically increase when the fuel includes biobased materials.
In a light microscope at 400x magnification the fouling/microbes can look something like in the image above. It can be fungi or alge which grow on the filter or in the fuel and their filaments or hyphae can cause clogging of the filter. We can help you determine if it is fouling from microbes which causes the filter clogging or if it is mainly, for example, a chemical problem. If the problem is mainly chemical in nature we can also do chemical analyses to determine the root cause.