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HOW TO: Change a Fuel Filter on a Diesel Engine

How long has it been since you replaced your fuel filter?

 

Merlin Diesel Systems Ltd stock a comprehensive range of 100% OEM quality oil, fuel, air, and hydraulic filter products to complement our traditional background of fuel injectors, fuel pumps, diesel fuel injection components and test equipment.

We stock a wide variety of trusted filter brands (pictured below) with over 4000 different filter references in stock to help protect and improve the performance of your engine.

Filter Supplier Logos

 

For any information on our filter range, please contact:

OR, click on the images below to be directed to our ‘Parts’ Page.

 

This article maps out: the importance of changing fuel filters; a list of crucial signs when a fuel filter should be replaced; a step-by-step guide on how to change a diesel engine fuel filter; and appropriate links to our filter range.

Fuel Filters

Fleetguard, Mann and Delphi Fuel Filters

 

What Fuel Filters Do

A diesel fuel filter extracts dirt, debris and other contaminants and impurities from the fuel before it reaches the injectors to power the engine. This ensures that the fuel is clean before it travels through the fuel system.

Most diesel vehicles may have two diesel fuel filters: a ‘primary’ filter and a ‘secondary’ filter, however this can differ from vehicle to vehicle. The purpose of the filters is:

  • Primary Filter: This is typically located between the vehicle’s fuel tank and the engine. This provides the fuel with an initial cleaning before it reaches the fuel transfer pump.
  • Secondary Filter: This is usually located near the engine and allows the fuel to have a more robust, final clean before it reaches the fuel injectors.

 

Fleetguard Fuel Filter

Fleetguard Fuel Filter [stocked at Merlin Diesel]

 

Importance of Changing Fuel Filters

It is crucial that a diesel fuel filter is replaced as clogged or damaged filters can result in unnecessary strain on the vehicle and, thus, poor fuel efficiency. Poor functioning diesel filters would also, overtime, result in damage to the vehicle’s engine and fuel injectors due to the lack of clean fuel reaching these components.

Typically, for the utmost maintenance of the diesel fuel filter, filters should be changed every 10,000 to 25,000 miles, however this can depend largely on: how frequently the vehicle is used; what type of vehicle holds the diesel filter; and how the occupant drives the vehicle.

 

Mann Fuel Filter

Mann Fuel Filter [stocked at Merlin Diesel]

 

When to Replace a Fuel Filter

  • THE ENGINE HAS DIFFICULTY STARTING

A common reason for trouble starting an engine can be due to a clogged fuel filter. The clean fuel cannot pass through the filter. Thusly, the fuel has become congested due to the high content of contaminants that, otherwise, would have passed freely through a new or clean diesel filter. In the short-term, changing a fuel filter is generally a quick and easy process and can save a great deal of time, stress, and money long-term if a clogged fuel filter is to cause your vehicle further damage.

  • THE VEHICLE STRUGGLES TO ACCELERATE OR DRIVE AT LOW SPEEDS

If your vehicle is having trouble accelerating, it could be a sign that your fuel filter is blocked. A blocked fuel filter means that the fuel system cannot inject enough fuel into the engine to allow the vehicle to travel effectively. Also, if your vehicle experiences harsh ‘jolts’ when accelerating, this consequently may be due to a clogged fuel filter.

  • THE ENGINE IDLING IS ROUGH

When a vehicle is not moving, the idling, or ‘running’, of the engine should be relatively smooth. When a fuel filter is obstructed with debris, this negatively impacts the smooth running of the engine. Poor engine idling can be indicated through a rough-feeling or shaky as your vehicle runs. A replacement of the fuel filter can ensure that the vehicle idles smoothly.

  • THE ENGINE LIGHT APPEARS OFTEN OR ALL THE TIME

A vehicle’s fuel pressure sensor monitors the fuel system. A clogged fuel filter can be detected by the pressure sensor monitors due to the lack of fuel passing through the filter and reaching the engine, which may be causing the engine light to appear on your vehicle’s dashboard.

  • THE ENGINE STALLS

Even despite a ‘smooth’ engine start-up, unexpected engine stalling can also be a consequence of poor fuel filter quality. This is due to high stress transferring onto the vehicle engine to attempt to receive fuel from a jammed fuel filter.

 

To spot the signs of a poorly functioning fuel filter and to ensure the smooth ‘sailing’ of your vehicle,

REMEMBER: ‘SAILS

  • Starting
  • Accelerating
  • Idling
  • Lights on dashboard
  • Stalling

 

Delphi Fuel Filter

Delphi Fuel Filter [stocked at Merlin Diesel]

 

Steps to Replace a Fuel Filter

  1. ENSURE YOUR ENGINE IS SWITCHED OFF

 

  1. LOCATE THE OLD (PRIMARY) FUEL FILTER

Your fuel filter can be located using your vehicle manual. Otherwise, the primary fuel filter is typically located between the vehicle’s fuel tank and engine. You may need to jack the car up to easily access the fuel filter.

 

  1. DETACH THE OLD (PRIMARY) FUEL FILTER

Place a container underneath the old filter as your remove it to prevent any spillages from excess fuel. If your filter is attached through fittings, use a wrench or screwdriver to loosen the filter’s fittings or, otherwise, unclip the filter brackets to detach the filter. You could use tape or caps to temporarily cover the fuel line to prevent further spillages during the transfer.

 

  1. INSTALL THE NEW (PRIMARY) FUEL FILTER

Secure the new filter and reattach any fittings or clips that were loosened in the previous step.

 

  1. LOCATE THE OLD (SECONDARY) FUEL FILTER

Your fuel filter can be located using your vehicle manual. Otherwise, the secondary fuel filter is typically located near the engine.

 

  1. DETACH AND INSTALL NEW (SECONDARY) FUEL FILTER

Repeat steps 3-4 on the secondary fuel filter.

 

  1. CHECK FOR LEAKS

Before starting your engine with your newly fitted fuel filters, ensure there are no leaks coming from the filters. If there are leaks, the filter may not have been fitted correctly and could cause damage to the vehicle if not refitted properly. Once accurately fitted, ensure that your engine starts properly. This may take a few attempts to the allow fuel pressure to be replenished.

 

  1. RECYCLE OLD FUEL FILTERS

Your old fuel filters cannot be disposed of simply by being discarded for landfill as they contain harmful chemicals that can negatively impact the environment. Instead, ensure that you recycle your old fuel filters at an autoparts centre.

 

 

Availability of Fuel Filters

When changing or replacing other components of your vehicle, you must ensure that you consider the condition of your fuel filter and how long it has been since it was replaced.

When diagnosing common rail pump or injector faults, it is crucial that the fuel filter is examined for swarf.

Swarf would indicate fuel contamination and the likely imminent failure of the fuel pump.

When replacing the fuel pump or injector, it is recommended that the fuel system be thoroughly cleaned and the fuel filter replaced every time.

 

Merlin Diesel Systems Ltd supply a wide variety of trusted filter brands (seen below)

Filter Supplier Logos

 

And stock filters for:

Filter Stock

 

For more information on our filter range, please visit or contact:

 

Want to read more of our insightful blogs about the products and services we offer at Merlin?

Here are a few of our latest posts to read up on:

 

 

Keywords: Filter, Fuel, Oil, Air, Hydraulic, Fuel Filter, Filter Replacement, Stock, Diesel, Merlin

 

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