Noun
a filter in the fuel line that screens out dirt and rust particles from the fuel
Source: WordNetThe fuel filter must be replaced much more often on a diesel engine than on a petrol engine, changing the fuel filter every 2–4 oil changes is not uncommon for some vehicles. Source: Internet
The water trap (which is sometimes part of the fuel filter) often has a float connected to a warning light, which warns when there is too much water in the trap, and must be drained before damage to the engine can result. Source: Internet