Adjusting Fass Fuel Pressure Regulator: A Step-By-Step Guide

The FASS Fuel Pressure Regulator is a device that allows users to fine-tune their fuel pressure to meet the exacting requirements of modern diesel trucks. It is manufactured from 6061 T-6 aircraft-quality aluminium and comes with a four-year warranty. The regulator is fully adjustable from 0-100 PSI and can be retrofitted to Titanium Series or Titanium Signature Series Systems for custom applications. FASS Fuel Systems also includes a boost compensation port, allowing users to run an airline from the intake manifold to increase fuel pressure during periods of high fuel demand. While FASS and Airdog's electronic lift pumps do not typically come with a way to adjust fuel pressure, this article will explore some options for doing so.

FASS adjustable fuel pressure regulator features

The FASS adjustable fuel pressure regulator is a highly customisable component that can be tailored to meet the needs of various diesel engines, particularly those with modified injection pumps and high-output injectors. Here are the key features of the FASS adjustable fuel pressure regulator:

Full Adjustability (0-100 PSI)

The regulator allows for precise adjustments within a wide range of 0 to 100 PSI, catering to the diverse requirements of today's diesel trucks. This adjustability ensures that drivers can fine-tune their fuel pressure to match their specific engine needs.

Boost Compensation Port

FASS has engineered a boost compensation port into the regulator, which is a beneficial feature when dealing with increased fuel demand during active acceleration. This port allows you to connect an air line from your intake manifold, so that as boost pressure rises, the regulator delivers a corresponding increase in fuel pressure.

Large 1/2" MPT Ports

The FASS regulator features large 1/2" MPT ports for inlet, outlet, and return functions. These larger ports promote smoother fuel flow and can handle higher fuel demands.

Gauge Port (1/8" MPT)

The regulator also includes a gauge port with a standard 1/8" MPT size, allowing for easy connection to fuel pressure gauges for monitoring and diagnostics.

High-Quality Construction

The FASS adjustable fuel pressure regulator is manufactured using 6061 T-6 aircraft-quality aluminium, ensuring durability and high standards. This choice of material contributes to the regulator's overall performance and longevity.

The FASS adjustable fuel pressure regulator offers a comprehensive solution for diesel engine owners seeking enhanced control over their fuel pressure, with the added benefit of a 4-year warranty for peace of mind.

How to adjust FASS external fuel pressure regulator

To adjust a FASS external fuel pressure regulator, you will need to have a basic understanding of the FASS fuel system and its components. The FASS fuel pressure regulator is designed to allow fine-tuning of fuel pressure to meet the requirements of modern diesel trucks. This is especially important for drivers with modified injection pumps or high-output injectors, where a standard pre-set lift pump is insufficient.

The FASS fuel pressure regulator offers full adjustability from 0-100 PSI. To adjust the regulator, follow these steps:

• Locate the regulator on the return side of the pump.
• Connect a -06 line from the outlet of the pump to the inlet of the fuel pressure regulator.
• Plumb the bottom port (relief/return port) of the regulator into the tee fitting of the lift pump.
• Ensure the tee fitting is also plumbed into the injector return and exits to the tank.
• Adjust the pressure according to your requirements, using the "clicker"-style knob on the regulator.

It is important to note that FASS fuel systems typically do not have an easy method to adjust fuel pressure. If your pump does not have an external/adjustable regulator, it likely uses a spring and ball system to regulate fuel pressure. In this case, you may need to contact the pump manufacturer for the appropriate springs to achieve the desired pressure.

Additionally, ensure that your return line is not limiting flow, as this can impact your ability to adjust the pressure properly. If needed, consider running a separate dedicated return line from the regulator directly to the tank for better adjustability.

How to avoid pressure creep when adjusting blocking style fuel pressure regulators

To avoid pressure creep when adjusting blocking-style fuel pressure regulators, it is essential to understand the root cause of this issue. Pressure creep occurs when the regulator's design necessitates additional force to completely shut off the inlet pressure from reaching the outlet port, resulting in a spike in fuel pressure as the valve closes. This typically happens when fuel pressure reaches the maximum value that the blocking-style regulator has been set to.

To prevent pressure creep, the small amount of fuel flowing through the regulator during adjustments must be maintained. This can be achieved by operating the engine at idle speed, which is the most common method. However, this approach may not always be feasible, especially when adjustments need to be made with the engine turned off but the fuel pump energised. In such cases, the use of bleed returns can simulate a flow rate, also known as trickle flow.

• Plumb a permanent -3AN fuel return line from the outlet port(s) to the fuel tank. This provides sufficient restriction, while using a -6AN line might result in too much flow, affecting the accuracy of readings.
• If additional regulators are present, more lines can be plumbed.
• If an unused port is connected to a -3AN line, it can be left in place as the restriction is enough to not cause capacity issues. Otherwise, the line can be disconnected when not in use, and the outlet plumbing can be reattached to the regulator.
• Establish an external flow source by setting up a temporary fuel line that directs 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 methods, you can effectively avoid pressure creep when adjusting blocking-style fuel pressure regulators, ensuring more accurate and consistent adjustments.

How to adjust fuel pressure with erratic fuel pressure readings

To adjust a FASS fuel pressure regulator, you need to adjust the fuel pressure to meet the exacting requirements of your vehicle. This is done by adjusting the regulator from 0-100 PSI to meet your needs. FASS fuel pressure regulators also have a boost compensation port, which allows you to run an airline from your intake manifold, so that as additional air pressure (boost) is seen, the regulator will deliver incrementally increased fuel pressure. This is beneficial during active acceleration when fuel demand has increased.

Now, if you are experiencing erratic fuel pressure readings, there are a few things you can try. Firstly, check if your pump has a way to adjust the fuel pressure. If not, your pump likely uses a spring and ball to regulate fuel pressure. The springs provided can sometimes be inconsistent, leading to erratic fuel pressure readings. You can try straightening and reinstalling the spring or replacing it entirely.

Another potential fix is to check the ball used in your pump. FASS typically uses a Buna ball, while Airdog uses a Viton ball. The Viton ball is made of stronger material, so trying this alternative might solve the issue.

Additionally, if you are still experiencing lower pressure issues, you can try putting a washer in to shim the spring and raise the pressure. Make sure to double-check the measurements to ensure you are not adding any additional restriction.

If you are still experiencing issues, you could try installing an external FPD (fuel pressure damper). This solution has been suggested by other users experiencing erratic fuel pressure readings and has reportedly worked for them.

Finally, ensure that your vacuum lines are routed correctly and that your return line is not clogged or blocked, as this can also cause erratic fuel pressure readings.

How to adjust FASS fuel pressure regulator with boost compensation port

Adjusting a FASS fuel pressure regulator with a boost compensation port is a straightforward process that can be done to meet the exacting requirements of many of today's diesel trucks. Here's a step-by-step guide on how to do it:

Step 1: Understanding the FASS Fuel Pressure Regulator

The FASS Fuel Pressure Regulator is designed to fine-tune fuel pressure, especially for diesel trucks with modified injection pumps and high-output injectors. It allows you to set the pressure from your lift pump to meet your specific requirements, ranging from 0 to 100 PSI. The regulator also features a boost compensation port, which enables you to connect an air line from your intake manifold. This connection ensures that as additional air pressure (boost) is detected, the regulator will deliver a corresponding increase in fuel pressure, benefiting acceleration and meeting increased fuel demands.

Step 2: Accessing the Regulator

Before making any adjustments, locate the FASS fuel pressure regulator in your vehicle. It is typically installed in the fuel system, connected to the intake manifold, and easily accessible for adjustments. Refer to your vehicle's manual or consult a mechanic if you're unsure about its location.

Step 3: Adjusting the Fuel Pressure

Once you have located the FASS fuel pressure regulator, you can adjust the fuel pressure by turning the "clicker" style knob. This knob allows for fine-tuning the pressure to meet your specific requirements. Make sure to adjust the pressure according to your vehicle's needs and within the 0-100 PSI range.

Step 4: Utilizing the Boost Compensation Port

To take advantage of the boost compensation port, connect an air line from the intake manifold to the port. This connection ensures that the regulator receives additional air pressure (boost) information. As a result, when you accelerate and the air pressure increases, the regulator will automatically deliver incrementally higher fuel pressure. This feature ensures a seamless and powerful driving experience, especially during active acceleration and increased fuel demand.

Step 5: Testing and Fine-Tuning

After making your adjustments, start your vehicle and let it idle. Observe the fuel pressure gauge (if available) and take note of any changes in engine performance. Fine-tune the fuel pressure as needed to ensure optimal performance and stability. It is important to make small adjustments and gradually work your way up to the desired pressure to avoid any potential issues.

Step 6: Road Testing and Final Adjustments

Take your vehicle for a test drive, preferably in a safe, open area. Pay attention to how the vehicle performs under different driving conditions, such as idle, acceleration, and cruising. Make final adjustments to the fuel pressure as needed to ensure a smooth and responsive driving experience. Remember to always follow recommended safety procedures when working on your vehicle and refer to a professional mechanic if you have any concerns or questions during the adjustment process.

Frequently asked questions