لجن یا آشغال در محفظه فیلتر سوخت

Sediment collected in the fuel filter's housing, restricting flow or being carried downstream. The housing is a settling chamber as well as a filter mount, so what accumulates there is a direct sample of what is in the tank.

Finding it is a finding about the tank rather than the filter. Rust from a steel tank, microbial growth in diesel, or debris from a disintegrating pump all end up here — and a new filter dropped into a dirty housing blocks quickly. Clean the housing whenever the filter is changed, which is routinely skipped. A vehicle that blocks filters far short of their interval has a tank problem, and replacing the filter again is treating the symptom.