Fuel filter change

[white90]

One of a small batch of basic Tech threads - the fuel filter should be replaced at recommended intervals, but rarely is. People suppose that fuel out of the service station pump is clean, and that a filter on the vehicle has little to do. Not so - an old filter is usually loaded with muck that was either in the fuel when you put it in, or fell in by some other means. Syptoms of a clogged filter are restricted revs and lumpy or non-existent tickover.

Changing the filter is relatively straight forward, but a bit messy, and the design of the vehicle means that it's almost impossible to stop fuel from spilling out. Location of the filter is on the bulkhead on all L/R's, this one is on a 2.5 N/A 90.

The new filter comes with new 'O' rings, and it's important to replace them as well. If your filter doesn't have a water drain in the bottom, then there is one too many with the filter.

There's a long bolt (11mm head), that passes through the top of the filter housing, through the centre of the filter, and into the base. The effect is to clamp the top and bottom together with the filter in the center. The filter has a large 'O' ring either side, and this completes a fuel-tight seal.

The bolt also has a small o-ring on, which has to be replaced with a new one supplied with the filter.

Place a suitable container (I use a 2 1/2 litre anti-freeze bottle with one side cut out), under the filter and remove the bolt. The base, filter, and around 1/4 litre of diesel will fall into the container.

Quite a build-up of debris in the bottom of the filter.

This o-ring has to be replaced as well with a new one that comes with the filter - put a thin film of grease on it - the new filter might bind and push it out of the groove.

The largest of the two o-rings in the kit fits into the groove you can see around the circunference of the filter housing.

Smaller one goes in the groove in the base of the filter housing.

Place the new filter on the base - the correct way up, and tighten the bolt - not head-throbbing tight, but enough to slightly compress the seals that are either side of the new filter.

The system has now to be bled - the lift pump has a lever on it for this purpose.

Place a thick wad of cloth under the injector pump, and undo the bleed screw a couple of turns with an 8mm spanner.

As you pump the lever, fuel will be sucked up from the tank to fill the empty new filter and any air in the system will be expelled through the bleed screw. Once there is a clear jet of fuel from the bleed - tighten the screw back up, and that should be it.

Start the engine and allow it to tick over - check for leaks, and if there are none, then that's it finished.

One thing to note - the lift pump is driven by an off-set lobe on the cam, and if the engine happens to have stopped with the pump diaphragm compressed, then the hand pump lever won't work. Just briefly flick the ignition to move the camshaft a bit, and you should then be able to do the job.

Les.