D4d Fuel Filter. Can Drain/clean Or Must Change?

[davestringer]

I seem to have bought some bad diesel from a supermarket (Morrisons at Boroughbridge, next to A1). I want to clean out the fuel filter if possible but can't see how. Tried everything that looks like it should unscrew on the filter including a plastic wing-nut underneath it but wouldn't budge. Don't want to force it and break it. Are these sealed units? Do I have to change the whole thing? What is the function of the button thingy on the top?

[GLIExec]

They can be a fiddle to get to, the easiest thing to do is remove the whole primer pump/heater assembly with the filter still attatched. Remove the pipes either side of the filter & plug them with a couple of screws to prevent you covering everwhere with diesel, disconnect the 2 connectors, one is the fuel heater, the other is the filter drain warning switch then remove the 2 bolts holding the whole assembly to the bulkhead. You'll then be able to replace the filter as a whole if required or remove the wingnut at the bottom & drain it out, also pump out any remaining fuel by pressing the primer pump a few times (the button on top ;) Refit then pump the primer again untill resistance is felt, if you do not do this, the engine will not run as it will cause an airlock at the diesel pump. Worth noting if you ever run out of fuel & wonder why it won't start after filling up!