Replacing Fuel Pressure Regulator In 2006 Wrx: Step-By-Step Guide

If you're looking to replace the fuel pressure regulator (FPR) on your 2006 WRX, you've come to the right place. This is a job you can do yourself, but it's important to take the necessary precautions and follow the correct steps to avoid damaging your engine. Before you begin, make sure to wear safety goggles as you will be working with fuel lines. In this guide, we will walk you through the process of replacing the FPR on your 2006 WRX, including locating the FPR, depressurizing the fuel lines, removing the old FPR, and installing the new one.

Location of the fuel pressure regulator

The fuel pressure regulator (FPR) on a 2006 WRX is located on the passenger side of the engine bay, underneath the manifold and the inlet hose. It sits to the right of the stock turbo inlet and is placed next to the air intake box.

To access the FPR, you will need to remove the air intake box on the passenger side. You will see two 10mm bolts that need to be removed, along with loosening the clamp on the fuel line to carefully wiggle out the FPR. It is important to be cautious during this process to avoid damaging the vacuum line connected to the intake manifold.

The vacuum line is prone to popping off, so it is crucial to secure it with zip ties as a preventive measure. Additionally, ensure that you are wearing safety goggles when working with the fuel line. Before beginning any work, depressurise the fuel lines by pulling the E/G fuse from the fuse box and cranking the engine a few times.

Removing the old regulator

To remove the old regulator on your 2006 WRX, begin by putting on safety goggles and removing the E/G fuse from the fuse box. Then, crank the engine a few times to depressurise the fuel lines.

The fuel pressure regulator (FPR) is located on the passenger side of the engine bay, next to the air intake box. Remove the two 10mm bolts holding the FPR in place, and carefully loosen the clamp on the fuel line. Gently wiggle the FPR to remove it, being careful not to damage the vacuum line connected to the intake manifold.

Securing the vacuum line with zip ties is an important step to prevent it from popping off, which is a well-known problem with this model. If the O-ring is worn or damaged, it should be replaced. You can also apply a small amount of lube or dish soap to the O-ring before reinstalling it.

Installing the new regulator

To install the new fuel pressure regulator, you will need to begin by relieving the pressure in the fuel system. Remove the E/G fuse from the fuse box and crank the engine a few times to depressurise the fuel lines.

The fuel pressure regulator is located on the passenger side, next to the air intake box. Remove the two 10mm bolts, and carefully loosen the clamp on the fuel line, slowly wiggling it out to remove the regulator. Be careful not to damage the vacuum line, which is connected to the intake manifold.

Zip ties can be used to secure the vacuum line, as it is known to pop off. Replace the O-ring if necessary, and be careful not to over-tighten the bolts. A small amount of lube or dish soap can be applied to the O-ring before installation. Ensure you are using a Viton O-ring, as regular rubber will fail when used to seal fuel.

Finally, install the new fuel pressure regulator, following the above steps in reverse.

Securing the vacuum line

To secure the vacuum line when changing the fuel pressure regulator on a 2006 WRX, follow these steps:

Firstly, it is important to note that the vacuum line is connected to the intake manifold. This is a known problem area, so be sure to use zip ties to secure the vacuum line. This is the most important step in the installation process, as failing to secure the line can cause it to pop off and potentially lead to engine damage.

When removing the old fuel pressure regulator, be careful not to damage the vacuum line. Remove the two 10mm bolts, loosen the clamp on the fuel line, and slowly wiggle the fuel pressure regulator out. Once the old part has been removed, carefully install the new fuel pressure regulator, ensuring that the vacuum line remains intact and secure.

It is also recommended to wear safety goggles during this process, as you will be working with fuel lines. Before beginning, depressurise the fuel lines by pulling the E/G fuse from the fuse box and cranking the engine a few times.

Testing the new regulator

Step 1: Locate the Fuel Pressure Regulator

The fuel pressure regulator is typically located at one end of the fuel rail, which holds the fuel injectors in place. It is a small metallic cylinder with a thin vacuum hose connected to the top. Depending on your vehicle's configuration, you may also see an incoming fuel line and a return fuel line connected to it. However, on newer models, the fuel pressure regulator may be placed inside the fuel tank as part of the fuel pump assembly.

Step 2: Check the Vacuum Hose

Before proceeding, check the vacuum hose connected to the fuel pressure regulator. Ensure that it is tightly connected, as a loose hose can prevent the regulator from functioning correctly. Also, inspect the hose for any signs of damage or wear. If the hose is damaged, it should be replaced.

Step 3: Connect the Fuel Pressure Gauge

Most modern fuel injection systems have a Schrader valve or test valve located on the fuel rail. This valve is similar to the air valve on your tires. Connect your fuel pressure gauge to this Schrader valve. If your system lacks this valve or has an older fuel system, refer to your repair manual for the best way to connect the gauge. If there is no test port or you don't have the correct adapter, you can either remove the test port valve and connect the gauge directly or disconnect the fuel inlet line and use a T-adapter.

Step 4: Start the Engine and Observe Pressure

Start the engine and let it idle. Observe the fuel pressure gauge while the engine is running. Fuel pressure should remain within the specifications provided in your car repair manual. With the engine off, pressure should hold for about 5 minutes. Additionally, remove the vacuum line while the engine is running, and the pressure should rise. If it doesn't, there may be an issue with the fuel pressure regulator.

Step 5: Repeat the Process

Ask an assistant to turn the ignition key to the "On" position without starting the engine for 5 seconds, and then turn it off. Repeat this step at least 5 times to ensure consistent fuel pressure. Inconsistent pressure may indicate that the fuel pressure regulator is sticking.

Step 6: Compare Readings to Specifications

Compare the pressure gauge readings to the specifications provided in your repair manual. If the readings are lower than the specified pressure while the engine is running, there could be an issue with the fuel injector, fuel pump, fuel filter, anti-drain valve, or the fuel pressure regulator itself. If the pressure begins to drop soon after shutting off the engine, a leaking injector, leaking anti-drain valve, or problems with the fuel pressure regulator may be the culprit.

Step 7: Test for Maximum Pressure

If your previous test showed low fuel system pressure after shutting off the engine, you can perform a maximum pressure test to help locate the source of the problem. Connect the fuel pressure gauge as before, and place a rag over the fuel incoming line and another over the fuel return line. Start the engine, let it idle for a minute, and then turn it off. As the engine turns off, use pliers to squeeze and block the incoming and return lines. If the pressure remains steady, the fault is likely in the fuel pump anti-drain valve. If the pressure drops, you have either a leaking fuel injector or a faulty fuel pressure regulator.

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