How to Change a Diesel Fuel Filter
To change a diesel fuel filter, drain the water, replace the filter without letting dirt in, then bleed the air out before running under load. The steps below cover spin-on filters and cartridge elements.
How often to change a fuel filter
Follow the interval in the engine or machine manual; diesel fuel filters usually have their own interval, separate from the oil change. Change sooner when a fuel restriction indicator trips, the water-in-fuel warning keeps coming back, or the engine loses power under load after a tank of poor fuel.
Before you start
Stop the engine and let it cool. Keep flames and sparks away. Have the correct replacement, matched by part number, plus a drain pan, clean rags and gloves. Close the fuel shut-off valve if the machine has one.
Changing a spin-on fuel filter
- Drain the water from the separator bowl through the drain valve at the bottom.
- Clean around the filter head so dirt cannot fall into the fuel system.
- Unscrew the old filter. If a bowl or water sensor is fitted to it, remove it to reuse on the new filter.
- Check that the old gasket came off with the filter and wipe the sealing face clean.
- Fit the bowl and sensor to the new filter, with new O-rings where they are supplied.
- Coat the new gasket with clean diesel and screw the filter on by hand until the gasket touches, then add the turn printed on the filter. Do not prefill it with unfiltered fuel, which would reach the clean side.
- Open the fuel valve and bleed the air from the system.
Changing a fuel filter element
For cartridge housings, drain the housing, remove the cover and the old element, fit the new O-rings supplied with the element, insert the new element and tighten the cover to the torque the manual gives.
Bleeding air from the fuel system
Most machines have a hand primer pump on the filter head or an electric lift pump. Open the bleed screw if one is fitted, prime until fuel comes out without bubbles, close the screw and keep priming until you feel resistance. Start the engine, let it idle and check for leaks before running under load. On common-rail engines follow the maker's procedure and never loosen high-pressure lines.
Primary and secondary filters
If the machine has a primary filter or water separator and a secondary filter, the manual states whether both are changed at the same service. Replace each with the part matched to its own number: the two stages have different micron ratings.
Related products
Shop diesel fuel filters and water separators.
How the separator works: fuel water separator guide.
Not sure of the part number? Send us a photo of the old filter.