Running Dual Fuel Pressure Regulators: Is It Possible?

Running two fuel pressure regulators in line is possible, but it depends on the type of regulators being used. If you are using two non-return-style (blocking) regulators, this setup will not work as intended because the second regulator will default to the lower pressure setting. However, if you are using a combination of a non-return-style regulator and a return-style (bypass) regulator, this can be an effective way to control fuel pressure. This setup is often used in nitrous oxide systems, where the non-return-style regulator is set to a higher pressure to feed the nitrous stages, while the return-style regulator maintains a lower pressure for the carburetor. It is important to note that the non-return-style regulator must be placed before the return-style regulator in the fuel line for this setup to function correctly.

Using two fuel pressure regulators with a carbureted engine

First, let's understand the role of fuel pressure regulators. These components are critical in ensuring that the correct fuel pressure reaches the carburetor, optimizing engine performance. There are two main types of fuel pressure regulators: deadhead (or blocking) regulators and bypass regulators. Deadhead regulators are the simplest and most common type, placed between the fuel pump and the carburetor to restrict fuel flow and maintain pressure. Bypass regulators, on the other hand, bleed off excess fuel pressure, returning it to the fuel tank via a return line.

Now, when it comes to using two fuel pressure regulators, also known as a regulator manifold, it is possible and even advantageous in certain scenarios. This setup is particularly useful when using multiple carburetors or multiple stages of nitrous oxide injection. By employing a regulator manifold, you gain the flexibility to feed fuel to multiple components and adjust their fuel pressure individually. This ensures that each carburetor or stage receives the optimal fuel pressure for its specific requirements.

When installing two fuel pressure regulators, it's important to consider the plumbing arrangement. The ideal setup for a high-power street or strip application is to position the bypass regulator in the return line shortly after the carburetor. This allows fuel to flow through the carburetor before reaching the regulator, ensuring that fuel pressure is regulated effectively. It's also crucial to use the appropriate fuel line sizes, typically stepping down from a larger feed line (-10 AN) to a smaller return line (-8 AN) to avoid plumbing bulk.

Additionally, when using two fuel pressure regulators, it's essential to ensure that the return line is not restricted. A restricted or undersized return line can lead to a buildup of backpressure, hindering the regulator's ability to effectively bleed off excess fuel pressure. As a rule of thumb, using a return line that is the same size as the feed line is recommended to maintain optimal fuel flow.

By using two fuel pressure regulators with a carbureted engine, you gain the ability to fine-tune the fuel delivery to each carburetor or stage, maximizing engine performance and ensuring a consistent fuel supply. This setup is especially beneficial in high-performance applications where fuel demands are significantly higher.

Using two fuel pressure regulators with a nitrous kit

First, it is important to understand the purpose of each component. The nitrous kit, also known as an NO2 or N2O set-up, is used to increase the power output of an engine by supplying nitrous oxide, which acts as an oxidizer. The fuel pressure regulators (FPRs) are responsible for controlling the fuel pressure and ensuring a consistent supply of fuel to the engine.

When using two FPRs with a nitrous kit, it is essential to have a clear understanding of the plumbing and wiring. In this setup, the main NO2 line from the bottle should be connected to the nitrous FPR first and then to the other FPR before going to the carburetor. It is recommended to have a fuel pressure gauge at each FPR to allow for accurate adjustments.

To ensure the system works correctly, the correct plumbing must be used. A Y-block should be installed at the end of the -10 line, followed by a -8 line to the inlet of each regulator. Regulator number one should have two lines running to the carburetor, one for each bowl. Regulator number two should have a single line connected to the fuel solenoid, and the second port should be blocked off.

It is also important to set the correct fuel pressure. The nitrous plate should be flowed at 6 psi, and the nitrous bottle should be set to 900 psi. This can be adjusted by activating the system and watching the pressure gauge. The pressure should drop but quickly recover, maintaining 6 psi for a few seconds.

Additionally, it is recommended to use a Holley regulator on the nitrous side to prevent chattering when flowing low amounts of fuel.

When using two FPRs with a nitrous kit, it is crucial to monitor both fuel pressure and nitrous pressure to ensure the system is working correctly and safely.

Adjusting a static fuel pressure regulator

Understanding Blocking-Style Regulators

Blocking-style fuel pressure regulators are characterised by the absence of a fuel return line from the regulator to the fuel tank. Fuel enters through the inlet port, passes the fuel control valve, and is then distributed through an outlet port to the carburetor. The fuel flow and pressure are controlled by the fuel control valve, which is activated by a diaphragm.

Avoiding Pressure Creep

Blocking-style regulators can experience "pressure creep," which results in inconsistent fuel pressure readings during adjustments. This occurs when the regulator reaches its maximum set value, and the fuel control valve shuts off inlet pressure from reaching the outlet port. This creates a spike in fuel pressure, leading to potential over-pressurisation of the carburetor and overfilling of the float bowls.

Adjustment Procedure

To properly adjust a blocking-style regulator, pressure creep must be eliminated. This is achieved by maintaining a small amount of fuel flow through the regulator during adjustments. The most common method is to operate the engine at idle speed. However, there may be instances where this approach is impractical, such as when adjustments need to be made with the engine turned off or in nitrous oxide applications with an additional regulator.

Implementing Bleed Returns

In such cases, bleed returns can be utilised to simulate a flow rate (trickle flow). Here are a few ways to set up bleed returns:

• Plumb a permanent -3AN fuel return line from the outlet port(s) to the fuel tank. This provides sufficient restriction to prevent inaccurate readings.
• Use multiple -3AN lines for additional regulators. These lines can be left in place if connected to an unused port or disconnected when not in use.
• Establish an external flow source by quickly connecting a temporary fuel line to direct fuel 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.

By following these steps and maintaining a small fuel flow during adjustments, you can ensure accurate and consistent fuel pressure regulation, maximising the performance of your engine.

Troubleshooting a static fuel pressure regulator

• Engine Misfiring: A faulty fuel pressure regulator will cause the air-fuel ratio of the engine to be affected, resulting in the engine misfiring and not maximising its performance.
• Engine Not Starting: A bad fuel pressure regulator can cause very low fuel pressure, leading to insufficient fuel entering the engine and making it hard to start.
• Black Smoke from the Exhaust Pipe: Black smoke from the exhaust usually indicates that unburnt fuel is making its way into the cylinders and the exhaust manifold. This is often a sign of a rich air-fuel mixture, which can be caused by a faulty fuel pressure regulator.
• Fuel Odour Inside the Car: A failing internal diaphragm in the fuel pressure regulator can cause fuel odours inside the car or engine bay.
• Check Engine Light: A bad fuel pressure regulator can cause the check engine light to come on, indicating a fuel pressure issue.
• Loss in Acceleration: A faulty fuel pressure regulator can cause the engine's fuel pressure to be too high or too low, resulting in a drop in acceleration.
• Fuel Leakage: A damaged fuel pressure regulator diaphragm or outer seal can cause fuel leakage, leading to performance issues and unpleasant odours.
• Reduced Fuel Efficiency: A problematic fuel pressure regulator can cause the engine to use more fuel than necessary, resulting in decreased fuel efficiency.
• Weak Acceleration: The inability of the engine to achieve the perfect balance between air and fuel can lead to weak acceleration, which is often a sign of a bad fuel pressure regulator.
• Problems when Decelerating: A faulty fuel pressure regulator can cause excessive gasoline buildup, leading to engine backfire and difficulty in decelerating.

If you suspect a problem with your static fuel pressure regulator, it is recommended to consult a professional mechanic for a proper diagnosis and repair.

Troubleshooting a liquid-filled fuel pressure gauge

• Understanding the Basics: Familiarize yourself with the components and functioning of a liquid-filled fuel pressure gauge. This includes knowledge about the fuel control valve, diaphragm, spring, adjustment mechanism, and reference ports. Understand the differences between blocking-style (non-return) and return-style (bypass) regulators.
• Identifying the Issue: Start by identifying the specific problem you're trying to troubleshoot. Common issues with fuel pressure gauges include inaccurate readings, pointer flutter, leakage, or complete failure.
• Checking for Leaks: Inspect the liquid-filled fuel pressure gauge for any signs of leakage. Leaks can affect the accuracy of the gauge and are often caused by damage to the housing or improper sealing.
• Checking Fuel Control Valve: Ensure that the fuel control valve is functioning properly. In blocking-style regulators, a faulty fuel control valve can lead to "pressure creep," resulting in over-pressurization and float bowl overfilling.
• Inspecting the Diaphragm: Examine the diaphragm for any damage or debris. The diaphragm plays a crucial role in controlling fuel flow and pressure, and any obstruction or tear can impact the accuracy of the gauge.
• Adjusting the Spring: Verify that the spring is in good condition and properly adjusted. The spring controls the movement of the diaphragm, and incorrect adjustment can lead to inconsistent pressure readings.
• Verifying the Adjustment Mechanism: Check the threaded adjustment mechanism to ensure it is functioning correctly. This mechanism allows you to set the fuel pressure and should be adjusted while the engine is idling for greater consistency.
• Monitoring Reference Ports: Pay attention to the vacuum/boost reference ports, especially in forced induction applications. These ports compensate for boost pressure and can impact the accuracy of the gauge if not functioning properly.
• Comparing with Other Gauges: If possible, compare the readings of the liquid-filled fuel pressure gauge with other gauges in the system. This can help you determine if the issue is specific to the liquid-filled gauge or a broader problem.
• Considering Gauge Type: Evaluate whether a liquid-filled gauge is the best choice for your application. While liquid-filled gauges can reduce pointer flutter, they are more susceptible to temperature-related inaccuracies and leaks. Dry gauges may be more suitable in certain cases.
• Seeking Professional Help: If the issue persists or you're unsure about the troubleshooting process, don't hesitate to consult a professional mechanic or automotive specialist. They can provide expert guidance and ensure the issue is properly diagnosed and resolved.

Remember to refer to your vehicle's specific instructions and always exercise caution when working with fuel systems.

Frequently asked questions