Adjusting B&M Fuel Pressure Regulators: A Step-By-Step Guide

Adjusting the B&M fuel pressure regulator is a straightforward process. The B&M FPR is designed to replace the stock fuel pressure regulator and allow for adjustments to the fuel pressure. The installation process involves cutting the stock FPR and bolting the B&M FPR in its place, as per the instruction sheet provided with the product. It is important to ensure that the B&M FPR is compatible with your vehicle, as using an incompatible regulator can lead to issues with fuel pressure and pump performance.

Installing a B&M fuel pressure regulator

Step 1: Research and Selection

Before installing a B&M fuel pressure regulator, it is essential to ensure that it is compatible with your vehicle's fuel delivery system and fuel pump. Research the specifications of your fuel pump, including flow rate, maximum working pressure, and amperage draw. This information will help you select the appropriate B&M fuel pressure regulator for your vehicle.

Step 2: Preparation

Once you have purchased the B&M fuel pressure regulator, carefully read the instruction manual provided with the product. Familiarize yourself with the installation process and gather all the necessary tools and equipment. It is crucial to work with a clean setup, so ensure that you have cleaning materials such as carb cleaner and compressed air.

Step 3: Cutting and Bolting

As per the instructions provided by B&M, cut your stock fuel pressure regulator and bolt the new B&M regulator in its place. This process should be straightforward, but ensure that you follow the manufacturer's guidelines precisely.

Step 4: Fuel Rail Preparation

Before proceeding, it is essential to prepare the fuel rail. Mark the desired location for drilling, ensuring that nothing interferes with the installation when re-installing the fuel rail. Remove the fuel rail and the FPR, and drill a hole in the marked location. Thread the hole to accommodate the fuel pressure gauge. Blow out the rail with compressed air and clean it thoroughly with carb cleaner to eliminate any metal shavings that could cause issues in the fuel system.

Step 5: Fuel Pressure Gauge Installation

Install the fuel pressure gauge by screwing it into the drilled and threaded hole in the fuel rail. Secure it tightly to prevent leaks, and consider using products like Teflon tape for added security.

Step 6: Routing and Mounting

Determine the routing of the hose from the fuel pressure gauge to the desired mounting location. Cut the hose to the appropriate length and force the fitting onto the end. Remember to use Teflon tape on the threads to ensure a tight seal. Mount the gauge securely, using zip ties or a custom bracket, to prevent vibrations and potential damage during engine revving.

Step 7: Final Checks

Before starting the car, perform a thorough inspection of the entire fuel system, including fittings, hoses, and injectors. Check for any fuel leaks, ensuring that all connections are secure and tight.

Step 8: Fuel Pressure Adjustment

With the vacuum line to the FPR unplugged, the stock fuel pressure should be within the range of 35-40 psi at idle for most vehicles. You can adjust the B&M fuel pressure regulator to fine-tune the fuel pressure according to your specific requirements. However, it is important not to run extremely high pressure, as it can prematurely wear out the fuel pump and damage injector seals.

Note: It is always recommended to consult a professional mechanic or a trusted workshop if you are unsure about any aspect of the installation or adjustment process.

Installing a B&M fuel pressure gauge

Step 1: Prepare the Fuel Rail

Before beginning, ensure you have the correct B&M fuel pressure gauge for your vehicle. The B&M FPR for a 92-96 Lude, for example, is known to fit most Honda models.

First, mark where you want to drill on the fuel rail with everything hooked up to the car. This is to ensure that nothing interferes when you reinstall the rail. Next, remove the fuel rail and the FPR. Drill a hole into the marked spot on the fuel rail and thread it for 1/8" pipe thread. Blow out the rail with compressed air and spray it clean with carb cleaner to remove any metal shavings.

Step 2: Install the Gauge

The B&M fuel pressure gauge should be installed according to the manufacturer's instructions. Typically, it involves cutting the stock FPR and bolting the B&M FPR in its place. Ensure you have the correct tools and fittings for the installation.

Step 3: Seal the Connections

It is crucial to use the correct sealant for the connections to prevent leaks. While some sources suggest using Teflon tape or liquid Teflon sealant, others warn against using them on tapered fittings in the fuel system. A light coating of oil or a lubricant/anti-seize on the threads may be recommended. Always refer to the manufacturer's instructions and seek advice from professionals or experienced enthusiasts.

Step 4: Test for Leaks

Once the gauge is installed, start the car and monitor for any fuel leaks. Keep a close eye on the fittings, hoses, and injectors for any signs of leakage. Ensure all connections are tight and secure, and use hose clamps if necessary.

Step 5: Mount the Gauge

Decide where you want to mount the gauge and route the hose accordingly. Cut the hose to the desired length, and force the fitting onto the end. Again, use Teflon tape on the threads before tightening. You can use zip ties to attach the gauge to the firewall temporarily until you make a proper bracket for a more permanent installation.

Remember to refer to the manufacturer's instructions and seek professional advice if you are unsure about any steps in the installation process.

Avoiding pressure creep

Accurate and consistent fuel pressure is critical for maximum and consistent high performance. Therefore, accurate adjustment of fuel pressure is critical. This can prove challenging with Blocking Style fuel pressure regulators. Unless the proper adjustment procedure is followed, the regulator's design can cause "pressure creep", resulting in inconsistent fuel pressure readings during the adjustment process.

Understanding Pressure Creep

To understand pressure creep, let's review the functions of Blocking Style Regulators and Bypass Style Regulators.

Blocking Style Fuel Pressure Regulator

With a blocking style regulator, fuel enters through the inlet port and travels past the fuel control valve, which controls the fuel flow and pressure, and is then distributed through an outlet port to the carburetor. Blocking style regulators are characterised by the absence of a fuel return line from the regulator back to the fuel tank. When there is no fuel demand from the engine, the fuel flow is completely halted by the fuel control valve.

Bypass Style Fuel Pressure Regulator

In contrast, a Bypass Style Regulator has a fuel return line from the regulator back to the fuel tank. When there is no fuel demand from the engine, the fuel continues to flow and is rerouted away from the engine and back to the fuel tank.

Addressing Pressure Creep

Now, let's address pressure creep. As fuel pressure reaches the maximum value in a Blocking Style Regulator, the fuel control valve must shut off inlet pressure from reaching the outlet port. This action requires extra fuel pressure to fully shut the valve, creating a spike in fuel pressure as the valve closes. This is referred to as "Pressure Creep". Bypass Style Regulators do not experience this issue since fuel continues to flow.

Pressure creep can cause inconsistent fuel pressure readings, especially when the fuel control valve is fully closed and the engine is shut off, but the fuel pump is still energised. This inconsistency makes it challenging to accurately and consistently adjust fuel pressure.

Strategies to Avoid Pressure Creep

To properly adjust fuel pressure with a Blocking Style Regulator, pressure creep must be eliminated. This can be achieved by maintaining a small amount of fuel flow through the regulator while making adjustments. The most common method is to operate the engine at idle speed.

However, there are scenarios where this approach may not be feasible, such as when adjustments need to be made with the engine shut off but the fuel pump energised, or in nitrous oxide applications with an additional regulator that only activates under full throttle. In such cases, the solution lies in utilising bleed returns to simulate a flow rate (trickle flow).

• Plumb a permanent -3AN fuel return line from the outlet port(s) to the fuel tank. This line provides sufficient restriction to prevent throwing off readings. More lines can be plumbed for additional regulators.
• If the -3AN line is connected to an unused port, it can be left in place as it won't cause capacity issues. Otherwise, the line(s) can be disconnected when not in use, and the outlet plumbing reconnected to the regulator.
• Establish an external flow source by setting up a temporary fuel line that allows fuel to flow into a safe container outside the vehicle. This can be done using a "tee" fitting at the gauge port or a specialty adapter fitting placed inline in the outlet plumbing. The fuel line can be routed through a valve or orifice to restrict the flow to small amounts.

By implementing these strategies, you can effectively avoid pressure creep and ensure accurate and consistent adjustment of Blocking Style Regulators, leading to optimal engine performance.

Setting the base fuel pressure

Step 1: Understand the Basics

Before you begin, it is important to understand how fuel pressure regulators work. The B&M fuel pressure regulator is designed to adjust the fuel pressure according to the boost in the turbo. It is crucial to ensure that the fuel pressure is set correctly to avoid running lean or encountering performance issues.

Step 2: Check Stock Fuel Pressure

Refer to the manufacturer's guidelines or a mechanic to determine the recommended stock fuel pressure for your specific vehicle. For example, for a 1990-1999 Mitsubishi Eclipse, the stock fuel pressure at idle with the vacuum line off should be around 43.5 psi.

Step 3: Install the B&M Fuel Pressure Regulator

Follow the installation instructions provided with the B&M fuel pressure regulator. The process typically involves cutting the stock fuel pressure regulator and bolting the B&M regulator in its place. Ensure you have the correct B&M regulator for your vehicle's make and model.

Step 4: Set the Base Fuel Pressure

With the B&M fuel pressure regulator installed, it's time to set the base fuel pressure. Start by locating the threaded adjustment mechanism on the regulator. This mechanism allows you to adjust the fuel pressure. Using the appropriate tool, carefully adjust the mechanism to achieve the desired fuel pressure as per the manufacturer's recommendations.

Step 5: Verify Fuel Pressure

Once you have adjusted the base fuel pressure, it is crucial to verify that the regulator is set correctly. Use a fuel pressure gauge to check the fuel pressure at idle and with the vacuum line disconnected. Ensure that the pressure matches the recommended stock fuel pressure for your vehicle.

Step 6: Test and Fine-Tune

After setting and verifying the base fuel pressure, take your vehicle for a test drive. Monitor the engine's performance and fuel efficiency. If necessary, make fine adjustments to the fuel pressure regulator to optimize performance. Remember, the goal is to find the sweet spot that provides the best balance of power and fuel efficiency without running too lean or rich.

Step 7: Regular Maintenance and Checks

Fuel pressure can fluctuate over time due to various factors, so it is important to perform regular maintenance and checks. Periodically verify the fuel pressure and make adjustments as needed to ensure optimal engine performance.

Using a bleed return

There are a few ways to set up bleed returns for this purpose. One approach is to plumb a permanent -3AN fuel return line from the outlet port(s) to the fuel tank. The -3AN line provides sufficient restriction, while a larger line, such as a -6AN, would allow too much flow and affect the readings. If needed, more lines can be plumbed for additional regulators. If the -3AN line is connected to an unused port, it can be left in place as its restricted flow won't cause capacity issues. Alternatively, the line(s) can be disconnected when not in use, and the outlet plumbing can be reattached to the regulator or the unused outlet port can be plugged.

Another method is to establish an external flow source by quickly hooking up a temporary fuel line to allow fuel to flow into a fuel-safe container outside the vehicle. This can be achieved through different means, such as using a "tee" fitting or a specialty adapter fitting placed inline in the outlet plumbing, to which the fuel line is attached. The fuel line can also be routed through a valve or orifice to restrict the flow and allow only small amounts of fuel to pass through.

Using bleed returns to simulate flow rate is a valuable technique when adjusting a B&M fuel pressure regulator, especially in situations where keeping a small amount of fuel flowing through the regulator is necessary for accurate adjustments.

Frequently asked questions