The fuel filter is an item that hopefully shold give a long and trouble free life.
However several things can lead you to need to change them more frequently than normal.
The first is dirty fuel. This may sound obvious but it does happen. Some garages tanks are cleaner than others however in the UK you’ll usually be fine with normal service intervals.
The biggest cause of blocked filters is the use of biodiesel or poorly filtered veg oil or home brew fuel.
Biodiesel contains methanol which is used in the process but not removed in the manufacture of the fuel. This methanol is a very good solvent leading to the first few tanks of fuel removing all the gunk form the system and clogging up the fuel filter.
Another cause of blocked fuel filters is water in the fuel. If large quantities of water are present then this can cause the filter insides to swell causing it to effectively block itself. There is a water drain on the bottom of the fuel filter but how many of you out there have actually used it? I know I never do, as water contamination is far less common than it used to be.
I change my filter every second oil change so roughly every 20-30k miles.
Note if the priming bulb is sucked flat this does not mean the fuel filter is blocked, quite the opposite infact, it usually means the blockage is either in the priming bulb itself or in the fuel line that feeds it.
Remove both fuel pipes from the top of the filter.
Lift the fuel filter from its bracket, and unscrew the clamp.
Replace the new filter into the bracket and slide it back onto the bracket.
Ensure the water drain is closed on the base of the filter.
Replace the pipes noting the direction of fuel flow, – there is an arrow on the fuel filter usually, and use pipe clips to secure the pipes to the filter (if not fitted originally).
Loosen the bleed screw
Pump the priming bulb until bubble free fuel comes out of the bleed screw
Retighten the screw.
(It is usually not necessary to bleed the fuel through to the pump but if you need to then loosen the bleed screw on the pump and pump the priming bulb till bubble free fuel flows from it before retightening it).