How To Block The Return On A Fuel Pressure Regulator?

Fuel pressure regulators are an important part of a vehicle's fuel system, ensuring optimal engine performance, fuel efficiency, and emissions control. There are two main types of fuel pressure regulators: return-style (also known as bypass-style) and non-return style (also known as blocking-style). The question of whether the return can be blocked on a fuel pressure regulator is relevant to understanding the key differences between these two types.

Return-style fuel pressure regulators are characterised by the presence of a fuel return line from the regulator back to the fuel tank. This type of regulator maintains constant and effective fuel pressure, enabling accurate adjustments and consistent fuel delivery. On the other hand, non-return style regulators lack this fuel return line, reducing weight, complexity, and expense.

Blocking the return on a fuel pressure regulator would essentially convert it from a return-style to a non-return style regulator. This modification has its advantages and disadvantages. By blocking the return, you eliminate the need for additional fuel lines and fittings, simplifying the system and reducing weight and cost. However, this also means that excess fuel cannot be redirected back to the fuel tank, which can impact fuel pressure regulation and potentially lead to over-pressurisation issues.

Characteristics of Blocking the Return on a Fuel Pressure Regulator

Blocking style regulators are also known as non-return or traditional style regulators

Blocking style regulators, also known as non-return or traditional style regulators, are characterised by their lack of a fuel return line from the regulator back to the fuel tank. This means that fuel enters through the inlet port, travels past the fuel control valve, and is then distributed through an outlet port to the carburettor.

In a blocking style regulator, fuel flow and pressure are controlled by the fuel control valve, which is actuated by a diaphragm. The movement of the diaphragm is limited by a spring, and fuel pressure to the carburettor is set with a threaded adjustment mechanism. A vacuum/boost reference port allows the regulator to compensate for boost pressure with forced induction applications.

One of the main advantages of blocking style regulators is that they require no fuel return line and fittings from the regulator to the fuel tank, reducing weight, complexity, and expense. Additionally, multiple regulators (set at different pressures) may be used from one pump.

However, there are also several drawbacks to blocking style regulators. As fuel pressure reaches the maximum value, the internal valve must shut off inlet pressure from reaching the outlet side of the valve. This requires extra force (fuel pressure) to fully shut the valve off and creates a spike in fuel pressure that could over-pressurise the carburettor and overfill the float bowls.

Another issue is "pressure creep", which occurs when there is leakage of the fuel control valve in the closed position, causing fuel pressure to continue to build at the outlet and potentially over-pressurising the carburettor and overfilling the float bowls. Blocking style regulators are also more sensitive to debris, which can prevent the fuel control valve from completely closing and cause pressure creep.

Finally, blocking style regulators may not be suitable for blow-though forced induction systems as the design of the fuel control valve can create a significant fuel pressure differentiation between the inlet and outlet.

Return-style regulators are also called bypass regulators

Return-style regulators, also known as bypass regulators, are a common choice for a performance fuel system. They are characterised by a fuel return line from the regulator back to the fuel tank.

With a bypass-style regulator, fuel enters through the inlet port and travels past a fuel bypass valve/fuel return line port, which governs fuel flow and pressure. It is then distributed through an outlet port to the carburetor. The opening and closing of the bypass valve is limited by a spring. Fuel pressure to the carburetor is set with a threaded adjustment mechanism.

Return-style regulators offer constant, effective fuel pressure to the outlet port. Any pressure overage is bled off through the return port as needed. This enables fuel pressure to be set more accurately and it should remain constant regardless of load. This also results in longer pump life and quieter pump operation. The pump operates just hard enough to maintain pressure, instead of maintaining typically 10 to 20 higher psi (as with blocking-style regulators).

However, there are some drawbacks to return-style regulators. They require the added expense, complexity, and weight of additional fuel lines and fittings. The return line is also very sensitive to pressure drop, especially within very low-pressure ranges. Large return lines, 1/2-inch or higher, must be used with limited bends and direct return to unpressurized tanks or reservoirs.

Return-style regulators are a common choice for performance fuel systems

Return-style regulators, also known as bypass regulators, are a popular choice for performance fuel systems. They are designed to control fuel system pressure using a spring and diaphragm mechanism that can be either adjustable or preset. This type of regulator is typically installed between the fuel pump and carburetor or throttle body, or at the end of a fuel injection rail.

The process begins with fuel entering the regulator through the inlet and exiting through the outlet to the carburetor or fuel injection system. A plug built into the diaphragm rests in the bypass port below the set fuel pressure. When the pressure exceeds the set limit, it pushes against the diaphragm and spring, lifting the plug and allowing excess fuel to be returned to the gas tank via the bypass port. This mechanism ensures that excess pressure is bled off, maintaining a constant and effective fuel pressure at the outlet port.

Return-style regulators offer several advantages over blocking regulators. They react more quickly to changes in engine load and provide more consistent and accurate fuel pressure, reducing Lean Condition spikes. This type of regulator is also less demanding on electric fuel pumps, as the pump only needs to maintain the set pressure. As a result, the pump produces less heat and noise, and enjoys a longer lifespan.

Additionally, the constant circulation of fuel in the system helps to keep the entire system cooler, reducing the risk of Vapor Lock and potentially increasing power output. However, it's important to note that return-style regulators require additional plumbing, including a Return Line with extra hoses and fittings. They may also not be compatible with certain fuel systems, such as those with multiple regulators set at different pressures.

Return-style regulators offer more consistent and accurate fuel pressure than blocking regulators

Return-style regulators, also known as bypass regulators, offer several advantages over blocking regulators. Firstly, they provide more consistent and accurate fuel pressure. This is achieved through the regulator's ability to react faster to changes in engine load, reducing Lean Condition spikes. The bypass valve in a return-style regulator opens and closes to maintain the set fuel pressure, ensuring a constant and effective fuel pressure at the outlet port. Any excess pressure is bled off through the return port, resulting in a more stable fuel delivery system.

Another benefit of return-style regulators is their positive impact on electric fuel pumps. By bleeding off excess pressure, the pump only needs to maintain the set pressure, resulting in reduced heat, noise, and longer pump life. The constant circulation of fuel also helps keep the entire system cooler, reducing the risk of Vapor Lock and potentially increasing power output.

However, it is important to consider the drawbacks of return-style regulators. They require additional plumbing, including a Return Line with extra hoses and fittings, which adds complexity and weight to the system. Additionally, return-style regulators may not be compatible with certain fuel systems, such as nitrous systems with multiple regulators set at different pressures. In such cases, the entire system will be limited by the regulator with the lowest pressure setting.

In summary, while return-style regulators offer more consistent and accurate fuel pressure through their ability to react to engine load changes and maintain a stable outlet pressure, they also introduce complexity and compatibility considerations. When choosing between return-style and blocking regulators, it is essential to weigh the benefits against the drawbacks to make an informed decision based on the specific requirements of the fuel system.

Return-style regulators are not always applicable

Return-style regulators, also known as bypass-style regulators, are not always applicable. They are not suitable for all fuel systems. For example, they are incompatible with a nitrous system that uses a single pump and multiple regulators set at different pressures. In such a case, the entire system will be limited by the regulator with the lowest setting, negating those set to higher pressures.

Return-style regulators are characterised by a fuel return line from the regulator back to the fuel tank. This additional plumbing results in added expense, complexity, and weight. The return line is very sensitive to pressure drop, especially within low-pressure ranges. Large return lines, 1/2-inch or higher, must be used with limited bends and direct return to unpressurised tanks or reservoirs.

Frequently asked questions