Changing the fuel filter - FQ101 The fuel filter is located towards the front of the car just behind the air duct. You don't have to, but if it makes it easier, remove the duct. It is held on with 3 plastic rivets. fuel filter changing - smartManiacs Re: fuel filter changing There are two fuel filters on the CDi smart. The main filter is a large, combination fuel filter and water separator. It looks like this:... It is two parts: the filter canister itself, and the electronic sender module that screws into the centre. Expect to pay 50 pounds or more for the two elements together.