How to Drain a Diesel Fuel Filter

Draining the water separator of your diesel fuel filter should be part of a regular service to ensure your engine receives clean fuel, and skipping this step could cause irreparable harm to both its system and engine.

A separator is an efficient device for extracting moisture from fuel. Usually found near or adjacent to a filter, it helps separate out excess moisture that might have found its way into your tank.

Remove the Fuel Tank

Clogged diesel fuel filters will cause your vehicle to burn more fuel. They will also put pressure on sensitive parts such as injectors and combustion chambers of your engine that could become compromised from dirty fuel; damaging these parts, making replacement more frequent.

Your diesel fuel filter should be changed regularly according to its recommended schedule found in your owner’s manual. Before beginning to change it, jack up your vehicle and place it on jack stands, leaving yourself enough working space underneath for changing it. Place a drain pan beneath the filter to catch any gasoline that may leak through, then locate and position the filter before using a hex tool or Allen wrench to unplug from its housing and loosen its cap and allow any remaining gasoline to drain into your drain pan before replacing its cap ensuring its new o-ring is properly seated against its ridge all around its ridge for best results.

Remove the Fuel Pump

A diesel fuel filter serves as the first line of defense against dirty fuel reaching engine injectors and potentially stalling when accelerating, or worse. When this filter becomes clogged it could have serious ramifications on car performance such as starting difficulties or even stalling when accelerating. Depending on its level of contamination it may require draining in full to restore proper functioning.

Fuel filters can often be found along the route from tank to engine. Once located, loosen any clips or banjo bolts connecting it with its associated fuel line and open up its clamps or banjo bolts for easier removal.

If the fuel filter features a vent valve at its top, release it. Otherwise, loosen or remove its drain plug or tap at its base and let the filter drain until clean diesel fuel comes pouring out, before closing its vent valve and returning it to service.

Remove the Fuel Filter

Clogged fuel filters can drastically decrease the amount of fuel delivered to an engine, leading to power losses and possibly increasing emissions. This is particularly relevant in diesel engines where they protect high-pressure components like injectors and injection pressure regulator valves used to set timing and pressure of injection processes.

Start by disconnecting the fuel filter cap from your tank shroud to prevent fuel spray from reaching your eyes and face while undertaking this delicate yet essential job.

Place a drain pan under the filter, and loosen and disconnect both ends of its fuel lines connected to it. Pliers may be needed to open any retaining clips at either end.

After removing the old filter, install a new one with a retaining clip or screw and hose clamp. Next, use a clean cloth to wipe down the housing and sealing surfaces of the new filter to remove any dirt or residue that has accumulated on them. Finally, add your o-ring that came with the filter against its cap ridge for optimal performance.

Remove the Water Separator

Diesel and gas fuels tend to absorb moisture from both atmospheric sources and natural condensation in storage tanks, which may then accumulate within their systems and result in misfiring and other costly damage if left accumulated for too long.

An efficient solution to this issue is a water separator. These devices are usually found near or at the fuel filter in a diesel engine bay and feature a clear plastic bowl that collects water, complete with drain valve and user viewing window for monitoring its level. Many also come equipped with handles making removal and replacement easy.

To keep their water separator functioning optimally, users should drain it regularly. Depending on fuel consumption and humidity levels, this could occur anywhere between once a week to two. It’s a relatively straightforward task that only involves loosening a nut with a spanner and pouring out all of the collected water into an appropriate container.