Mounting Fuel Pressure Regulators: Engine Cylinder Head Option?

The placement of a fuel pressure regulator is a contested topic. While some believe it should be placed close to the fuel's destination (fuel rail, fuel log, carburetor, diesel, or direct injection pump), others argue that it can be placed further away, even at the opposite end of the vehicle. The choice of location depends on various factors, including ease of installation, adjustment, and appearance. However, when it comes to performance, the distance between the regulator and the fuel destination plays a crucial role. The longer the fuel line, the greater the potential for fuel pressure loss. Therefore, mounting the regulator closer to the engine cylinder head can help improve fuel pressure regulation.

The best location for a fuel pressure regulator

Mounting the regulator close to the fuel's destination (fuel rail, fuel log, carburetor, diesel or direct injection pump) can improve pressure regulation by reducing the potential for fuel pressure loss. This is especially important for applications with high power demands, extra low fuel pressure systems, and high-g launches. In these cases, the proximity of the regulator to the fuel delivery destination can make a significant difference in performance.

On the other hand, for some applications, the impact of regulator placement on fuel pressure may be negligible. For example, in diesel systems with integrated relief valves or "lower power" gas or ethanol systems, the pressure error caused by placing the regulator away from the destination may not be significant. In such cases, ease of installation, adjustment, and appearance can take precedence when choosing a location.

Additionally, the type of fuel delivery system and fuel pump also play a role in determining the best location for the fuel pressure regulator. Most lever-style mechanical fuel pumps don't require a regulator, and some electric fuel pumps have a built-in regulator. For external regulators, the choice between a deadhead-style regulator and a bypass-style regulator will influence the installation process and the overall performance of the fuel system.

It's worth noting that while the fuel pressure regulator can be mounted to the engine cylinder head, it is crucial to ensure that it is securely fastened and does not interfere with any moving parts or critical components. Consulting with a mechanic or a professional in fuel system design can provide specific guidance for a particular vehicle or application.

Fuel pressure regulator mounting options

Mounting Location

The location of the fuel pressure regulator can vary, with some placing it close to the fuel's destination (fuel rail, fuel log, carburetor, or injection pump) and others opting for a more distant location, sometimes at the opposite end of the vehicle. The choice depends on the specific application and the importance of fuel pressure regulation versus ease of installation and aesthetics.

Performance Considerations

For high-power applications, such as drag racing vehicles subjected to high g-force launches, it is crucial to mount the regulator as close to the fuel delivery destination as possible. The longer the fuel line between the regulator and the fuel destination, the greater the potential for fuel pressure loss, especially during rapid acceleration. Therefore, a shorter fuel line can minimise fuel pressure errors and improve performance.

Convenience and Accessibility

Some individuals may choose to mount the regulator in a convenient and easily accessible location, such as the inner fender well or the firewall. This can facilitate adjustments and maintenance. However, others may prefer to mount it in an out-of-the-way location to achieve a cleaner, more streamlined look.

Fuel Delivery System and Pump Type

The type of fuel delivery system and fuel pump can influence the mounting options for the fuel pressure regulator. For example, some lever-style mechanical fuel pumps do not require a regulator, while some electric fuel pumps have a built-in regulator, eliminating the need for an external unit. In contrast, high-performance engines with higher fuel flow demands may require an external regulator capable of handling increased fuel pressure and flow rates.

Vehicle Type and Sanctioning Requirements

The type of vehicle and the sanctioning requirements of racing organisations can also impact mounting options. For instance, NHRA-sanctioned events at the drag strip may have specific regulations regarding the location of the fuel pressure regulator, such as maintaining a certain distance from the firewall.

Fuel pressure regulator installation

Installing a fuel pressure regulator (FPR) can be done in a few steps. The process is generally the same for most cars, although the location of the FPR and the fuel in/fuel out ports may vary.

Firstly, relieve the fuel pressure from your fuel lines. You can do this by removing the fuel cap and pulling the fuel pump fuse, then cranking the car. You may also want to consult your car's repair manual for this step.

Next, remove the old FPR. This is usually located at the front, near the fuel rail, and is held in place by a couple of screws. Once these are removed, carefully pull the FPR away from the fuel rail. You may need to loosen the clamps on the fuel hose first.

Now, you can install the new FPR. This should be done in reverse of the removal process. Ensure you add a little spit or Vaseline to the larger O-ring that goes into the fuel rail. You may also need to replace the O-rings, which can be done at home.

Finally, you can test the pressure and make adjustments. With the vacuum hose disconnected, the base fuel pressure should be around 43psi or 3Bar. When you reconnect the vacuum hose, the pressure will drop to around 34-37psi. You can adjust the FPR by loosening the lock nut and turning the hex key to raise or lower the pressure.

There are also a few things to consider when choosing a fuel pressure regulator. It's important to match the regulator to the type of fuel delivery system and fuel pump you are using. It's also worth checking if your fuel pump requires an external regulator, as some have them built-in.

Fuel pump and regulator compatibility

When choosing a fuel pressure regulator, it is important to ensure compatibility with the fuel delivery system and the fuel pump. The regulator is a critical component, and its compatibility with the fuel pump is essential for optimal performance and safety.

Firstly, it is worth noting that not all fuel pumps require a regulator. Most lever-style mechanical fuel pumps, for instance, do not need a regulator. Some electric fuel pumps even have a built-in regulator, eliminating the need for an external unit. These integrated regulator pumps are typically low-pressure units designed for use with carburetors only.

If your fuel pump does require an external regulator, it is important to research the pump's specifications, such as flow rate, maximum working pressure, and amperage draw. This information will guide you in selecting a compatible regulator. For example, the HZTWFC Fuel Injection Pump Common Rail System Regulator is designed for specific Mazda and Ford models, and it is essential to confirm compatibility before purchase.

Additionally, the type of regulator plays a role in compatibility. The two main types are deadhead-style and bypass regulators. Deadhead-style regulators are the simplest and most popular, especially for carbureted engines. They are placed between the fuel pump and the carburetor and use a restriction to lower fuel pressure by decreasing fuel flow. While these regulators are cost-effective, they may limit performance capabilities due to the lack of a return line.

On the other hand, bypass regulators, like the Holley unit, offer improved performance by bleeding off excess fuel pressure and returning it to the fuel tank. This design helps maintain stable pressure, react quickly to fuel flow changes, and prevent issues like pressure creep and vapor lock.

In conclusion, ensuring compatibility between the fuel pump and regulator is crucial for the safe and efficient operation of your engine. By considering the specific requirements of your fuel pump and selecting a suitable regulator type, you can achieve optimal performance and avoid potential issues.

Fuel pressure regulator maintenance

Fuel pressure regulators are essential for maintaining stable fuel pressure and ensuring that the correct amount of fuel is supplied to the vehicle's fuel injection system. While they don't often require maintenance, there are some things you can do to keep them in good condition and some signs you should look out for that indicate they need replacing.

Choosing and Installing a Fuel Pressure Regulator

When choosing a fuel pressure regulator, it's important to match it to your fuel delivery system and fuel pump. Some fuel pumps have a regulator built into them, so you won't need to purchase an external unit. If your fuel pump requires an external regulator, you can choose between a deadhead-style regulator and a bypass-style regulator. Deadhead-style regulators are simpler and more popular, but bypass-style regulators can help improve performance and prevent issues like pressure creep and fuel temperature increases.

Testing and Replacing a Fuel Pressure Regulator

The best way to check if your fuel pressure regulator is functioning properly is to use a fuel pressure gauge and disconnect the vacuum hose. If there is no change in pressure when the hose is disconnected, it likely means the regulator is defective and needs to be replaced. Most modern fuel pressure regulators are not adjustable, so if it is worn and resulting in incorrect fuel pressure, it will need to be replaced.

Signs Your Fuel Pressure Regulator Needs Replacing

• Hard starting or no start
• Stalling
• Poor acceleration
• Rough idling
• Decreased fuel economy
• Check engine light
• Backfiring sounds
• Problems starting when the engine is hot
• Black smoke coming from the exhaust pipe
• Fuel leaks

Maintenance Tips

While fuel pressure regulators don't require frequent maintenance, it is important to inspect and test them at the manufacturer's recommended intervals to catch any problems early on.

Frequently asked questions