Relieving Fuel Line Pressure: A Step-By-Step Guide

Knowing how to release pressure from a fuel line is an important skill for anyone who wants to perform maintenance on their car's fuel system. Before changing a fuel filter or removing a fuel line, it is crucial to relieve the pressure to avoid being sprayed by high-pressure fuel. There are several methods to do this, including disabling the fuel pump and starting the engine until it stalls, removing the CIRCUIT RELAY, or pressing on a Schrader valve on the fuel rail. It is also important to take safety precautions, such as wearing eye protection and using rags to catch any dripping fuel.

Remove the CIRCUIT RELAY

To remove the CIRCUIT RELAY, follow these steps:

First, locate the CIRCUIT RELAY. It is usually found in one of two plastic fuse boxes near the battery and is labelled "CIRCUIT RELAY" on the top of the fuse box.

Once you have located the CIRCUIT RELAY, you will need to disable the fuel pump. This can be done by pulling the fuel pump relay or tapping on the inertia switch. Alternatively, you can disconnect the negative battery terminal.

After disabling the fuel pump, start the engine and let it run until it dies. This will relieve the pressure in the fuel lines. Be prepared to catch any remaining fuel with a shop towel or rag as you work.

Now, you can proceed to remove the CIRCUIT RELAY. Pay attention to how it is connected, as you will need to install the new relay in the same way.

It is important to note that releasing fuel pressure can be dangerous if not done properly. Always refer to your vehicle's owner's manual for specific instructions and take appropriate safety precautions.

Turn off the ignition switch

Turning off the ignition switch is an important step in releasing the pressure from your fuel line. This is not something that should be rushed, and safety precautions should be taken.

Firstly, locate the CIRCUIT RELAY in one of the two plastic fuse boxes near the battery. It will be in the larger of the two boxes and will be labelled. Remove the CIRCUIT RELAY.

Next, you need to wait for the engine to stall. This is a crucial step, as it ensures that the pressure is released from the fuel line. Once the engine has stalled, you can turn off the ignition switch.

It is important to note that you should not attempt to remove the fuel filter or any fuel lines before releasing the pressure. If you do not release the pressure first, you will be squirted by high-pressure fuel.

After turning off the ignition switch, you can then install the circuit-opening relay. Remember to always refer to the manufacturer's instructions or a trusted mechanic for guidance on releasing fuel pressure.

Depressurise the fuel tank

Depressurising the fuel tank is an important step before replacing the fuel filter or removing any fuel line. If you don't do this, you will be met with a squirt of high-pressure fuel. Here are the steps to depressurise the fuel tank:

Firstly, remove the CIRCUIT RELAY. This is located in the larger of the two plastic fuse boxes near the battery and is labelled on the top of the fuse box.

Next, after the engine stalls, turn off the ignition switch. Then, install the circuit-opening relay. Finally, remove the gas cap to depressurise the fuel tank.

Use a rag as protection from fuel spray when disconnecting the hoses and plug the hoses after removal.

Another method to depressurise the fuel system is to disable the fuel pump and start the engine, letting it run until it dies. You can disable the fuel pump by pulling the fuel pump relay or tapping the inertia switch.

Alternatively, you can press down on the Schrader valve, which is located on the fuel rail. Place a shop towel under and around the Schrader valve, and with the key off, press a small screwdriver onto the valve until fuel stops dripping from the line.

Disconnect the hoses

To disconnect the hoses, you will need to relieve the pressure in the fuel lines. Here is a step-by-step guide:

Step 1: Remove the Negative Battery Terminal

First, remove the negative battery terminal. This will ensure that the electrical system is disconnected before you start working on the fuel lines.

Step 2: Prepare the Work Area

Place a shop towel, rag, or any other absorbent material under and around the Schrader valve. This will help catch any fuel drips or spills during the process.

Step 3: Release Pressure from the Schrader Valve

With the key off, use a small screwdriver to press the Schrader valve. The Schrader valve is located on the fuel line in the engine compartment. Keep pressing until fuel stops dripping from the line.

Step 4: Wear Safety Gear

Before proceeding, put on safety goggles and other appropriate safety gear. Working with fuel lines can be dangerous, so it is important to protect your eyes and body from any potential fuel spray or spillage.

Step 5: Disconnect the Hoses

Now you are ready to disconnect the hoses. Use a rag to protect yourself from any fuel spray and have a bucket or container ready to catch any fuel that may spill. Slowly and carefully loosen the clamps or bolts holding the hoses in place, then remove the hoses.

Remember to work slowly and carefully throughout the entire process. Fuel can be dangerous, and it is important to take the necessary precautions to ensure your safety.

Prime the fuel system

To prime the fuel system, you will need to follow these steps:

Firstly, locate the fuel pump. This is usually found between the fuel tank and the first fuel filter. You will then need to identify the manual primer on the pump, which can take the form of a lever or a plunger.

Next, open the bleed plug on the fuel filter closest to the fuel tank. Consult your vehicle's owner's manual for the exact location of the bleed plug. Then, open the fuel supply valve to allow fuel to flow from the pump to the filter. Again, the location of the valve will vary depending on the vehicle's make and model, so be sure to consult the owner's manual for specific details.

Now, it's time to prime the engine. Do this by either lifting and lowering the lever or pumping the plunger, depending on the type of primer your engine has. Continue this process until fuel escapes from the bleed-plug holes in a steady stream, without any air bubbles.

Once you have a steady stream, close the bleed plug and the fuel supply valve. Insert the key into the ignition and turn the engine over. If the engine doesn't start, simply repeat the process until it does.

You can also prime a mechanical fuel pump by locating the pump and removing its outlet line. Shine a flashlight into the pump's inlet while continuously cranking the engine until you can see the fuel. This method helps create pressure to ensure proper fuel delivery to the engine.

Additionally, it's important to note that you should release the fuel pressure before priming the fuel system. This will prevent excessive engine cranking during the first start.

Frequently asked questions