Changing Fuel Filters: Easy Diy Or Mechanic Job?

Changing a fuel filter is a simple and inexpensive procedure that can be done at home or by a mechanic. It is an important part of regular vehicle maintenance, as it ensures the fuel pump remains in good condition and prevents contaminants from entering the engine. Depending on the vehicle, the fuel filter is usually located along the fuel line, either under the car or in the engine bay, and should be replaced every two years or between 24,000 and 30,000 miles. The process involves relieving the pressure in the fuel system, removing the old fuel filter, and installing a new one, ensuring that the arrow on the filter points towards the engine.

Locating the fuel filter

The exact location of the fuel filter depends on the vehicle’s make and model. For example, 1995-2002 Honda Accord models have the fuel filter near the brake master cylinder on the back of the engine. In some vehicles, the fuel filter is located in the engine bay on the line that leads to the fuel rail. In others, it is placed underneath the vehicle, near the fuel tank. Some vehicles may place the fuel filter in a different location, so it is best to refer to your vehicle's service manual or consult an auto repair manual.

Before accessing the fuel filter, it is important to first relieve the pressure in the fuel system. This can usually be done by allowing your engine to run for a minute or so without the fuel pump functioning. To do this, locate the fuse or relay for your vehicle’s fuel pump and unplug it. Then, try to start the vehicle. If you have disconnected the correct circuit, the engine will turn over but not start, or it might start and run for a few seconds before dying.

Depressurising the fuel system

Locate and Remove the Fuel Pump Relay

First, locate and remove the fuel pump relay from its socket. The fuel pump relay is usually located in the fuse box under the hood of your vehicle. Once you have located it, simply pull it out.

Start the Engine

With the fuel pump relay removed, start the engine. Since the fuel pump will not be operating, the engine will eventually stall as there will be no supply of fuel. This will relieve the pressure within the lines, making it easier and safer to disconnect them later in the process.

Shut Off the Engine and Replace the Relay

Once the engine has stalled, shut off the ignition and replace the fuel pump relay or fuse.

Additional Tips

• It is important to wear safety glasses and have a drain pan or rag ready to catch any spills when disconnecting the fuel lines.
• Before beginning any work, ensure your vehicle is safely parked in an area with ample working space.
• If you are uncomfortable with any part of the process, it is best to consult a professional mechanic for assistance.

Removing the old fuel filter

Before removing the old fuel filter, it is important to relieve the pressure in the fuel system to prevent fuel from spraying out. To do this, locate the fuel pump fuse or relay in the fuse box and remove it. Then, start the engine and let it run until it stalls. This will depressurise the fuel system.

Now, with the fuel filter accessible, note its orientation, particularly if there is an arrow marking. The arrow represents the direction of the flow.

Loosen any hose clamps or mounting hardware from the fuel lines connecting to the fuel filter. As you remove the fuel lines from the old filter, gasoline may spill, so it is helpful to have a catch pan or rag to minimise any spills. If you are having difficulty removing the rubber lines from the filter, use a pair of pliers to gently pry the fuel line off the old filter. Be careful not to damage the fuel line in the process.

If your filter is held in place by a bracket, you will need to slide the fuel filter out of it. The fuel filter is likely to have a slight bell shape, allowing it to slide out in only one direction.

If your filter sits in the bracket differently, you may need to slide it toward the back of the car to remove it. Some fuel filters under the hood may be held in the bracket with a bolt that will need to be removed to slide the filter out.

Installing a new fuel filter

Prepare Your Vehicle:

• Park your vehicle in a safe and well-ventilated area with ample working space.
• Relieve the pressure in the fuel system by removing the fuel pump fuse or relay and allowing the engine to idle until it stalls.
• Disconnect the battery ground cable, marked with a minus sign, and set it aside, ensuring it doesn't touch any metal surfaces.
• Place a drain pan or container underneath the fuel filter to catch any fuel spillage.

Remove the Old Fuel Filter:

• Locate the fuel filter, which is usually found near the fuel tank, underneath the vehicle, or within the engine compartment.
• Remove any clips or mounting hardware securing the fuel lines to the fuel filter.
• Detach the fuel lines from the fuel filter by gently prying them off with a pair of pliers. Be careful not to damage the fuel lines.
• Slide or push the old fuel filter out of its bracket or housing.

Install the New Fuel Filter:

• Compare the new fuel filter with the old one to ensure they are the same size and will fit properly.
• Slide the new fuel filter into the bracket or housing, ensuring it is facing the correct way, with the arrow pointing towards the engine.
• Reattach the fuel lines to the new fuel filter and secure them with the appropriate clips or mounting hardware.
• Reinstall the fuse or relay for the fuel pump.

Test the Installation:

• Try starting the vehicle.
• Check for any fuel leaks around the new fuel filter.
• If there are no leaks, lower the vehicle and reconnect the battery.

By following these steps, you can effectively install a new fuel filter in your vehicle, ensuring a smooth and efficient fuel system.

Testing for leaks

Step 1: High-Pressure System Fuel Leak Test

This test will help you identify any leaks in the high-pressure fuel system, which includes the fuel pump, fuel lines, injectors, and the fuel rail.

• Start by steam cleaning the entire fuel system to remove any dirt or debris that may interfere with the test.
• Start the engine and allow it to reach operating temperature (140°F or 60°C).
• Perform the RPBO (Rail Pressure Bleed-Off) test. Refer to your vehicle's service manual for specific instructions.
• If the RPBO test passes, no further action is needed. If it fails, proceed to the next step.
• Inspect the high-pressure pump to rail feed fittings at the rail and the pump for any leaks or loose connections. Tighten any loose connections and retest. If leaks persist, replace the lines.
• Inspect the injector fuel line rail connections for external leaks or loose lines. Tighten any loose connections and retest. If leaks persist, replace the lines.
• Inspect the Fuel Rail Pressure Sensor for any leaks or loose connections. Tighten or replace the sensor if necessary.
• Inspect the PLV (Pressure Limiting Valve) connection for any leaks or loose connections. Tighten or replace the PLV connection if necessary.
• Inspect the high-pressure fuel pump for any external leaks. Replace the pump if leaks are found.

Step 2: Dye Test

If no leaks are found in the previous step, proceed with a dye test to check for smaller leaks.

• Turn off the ignition and install a fuel test bottle kit (part number J-48708). Fill one container with ultra-low sulfur diesel fuel and add fuel dye to the bottle.
• Connect the hoses from the kit to the fitting on the top of the fuel cap. This will isolate the engine from the chassis fuel system.
• Prime the fuel system using a hand primer until there is no air coming out of the return fuel line.
• Remove the rocker cover and install a tool (part number W470589009800) onto the rear of the cam frame to cover the cam gears.
• Start the engine and allow it to reach operating temperature (140°F or 60°C). Run the engine at 900 rpm.
• Using a black light, inspect the injectors and fuel lines for signs of leakage. Replace any leaking injectors or fuel lines.
• If no leaks are found, inspect the entire high-pressure system again with the black light. Repair any leaks that are found.

Step 3: Pressure Test

Another method for testing fuel system leaks is by pressurizing the system and checking for pressure loss or leaks.

• Locate the fuse or relay for the fuel pump and unplug it.
• Attempt to start the vehicle. If the correct circuit was disconnected, the engine will turn over but not start, or it may start and run for a few seconds before dying.
• Shut off the engine and allow it to cool if it was running.
• Connect a garden hose to a water source and have it ready near the vehicle.
• Put on safety glasses and drive the vehicle up on ramps if the fuel filter is mounted underneath and you need more clearance.
• Place a drain pan under the fuel filter to catch any spills.
• Locate the fuel filter and loosen or remove the fuel lines connected to it. Be careful as fuel may squirt out.
• Remove the screw clamp or bolts holding the fuel filter in place and place it aside.
• Pressurize the fuel system using a bike pump or similar tool. Pump until the system is a couple of psi above ambient pressure.
• Listen for any unusual sounds and check under the vehicle for any fuel leaks.
• If no leaks are found, open the fuel cap to release the pressure. If the return hose is still connected, it may spew fuel, so be cautious.

Step 4: Final Checks

Once you have completed the above tests and repairs, it is important to perform final checks to ensure the system is leak-free.

• Reinstall the fuel pump fuse or relay that was disconnected earlier.
• Attempt to start the vehicle. If it runs normally and there are no fuel leaks from the new filter, the job is done.
• If there are still signs of a leak, repeat the above steps to identify and repair the issue.

Frequently asked questions