Adjusting Fass Fuel Pump Pressure: Can It Be Done?

FASS fuel pumps are generally not designed to have their pressure adjusted easily. The pressure can be adjusted by modifying the spring inside the pump, which regulates the fuel pressure. This can be done by either stretching the spring or replacing it with a spring of a different strength. However, this process can be complex and may require purchasing additional parts. It is recommended to consult a professional or the manufacturer for guidance on adjusting the pressure of a FASS fuel pump to avoid any potential issues or damage.

FASS fuel pumps typically don't have an easy way to adjust fuel pressure

One way to adjust the fuel pressure is by modifying the spring and ball mechanism that regulates fuel pressure in the pump. The spring and ball are located inside the "air/vapor return to the tank" hose/fitting. By removing this hose/fitting, you can access the spring and ball. If the spring is twisted or damaged, it can cause erratic fuel pressure readings. You can try straightening or replacing the spring to resolve this issue. Additionally, FASS typically uses a Buna ball, while Airdog uses a Viton ball. You may experiment with using a Viton ball instead, as it is made of stronger material and may provide better performance.

Another way to adjust the fuel pressure is by adding a washer or shim to the spring assembly. This will raise the fuel pressure and can be adjusted by changing the thickness or position of the washer. It is important to note that the washer should be placed between the fitting and the spring, not between the spring and the ball.

It is also possible to adjust the fuel pressure by stretching the existing spring. This method involves carefully stretching the spring to increase the fuel pressure. However, it is important to note that this may not be as effective as using a thicker spring designed for higher fuel pressure.

Finally, you can also contact FASS support for assistance in adjusting the fuel pressure. They may provide guidance or recommend specific parts or springs to achieve the desired fuel pressure. It is recommended to consult with FASS or a qualified technician before making any modifications to your fuel pump to ensure safe and proper operation.

The pump may use a spring and ball to regulate fuel pressure

FASS fuel pumps typically do not come with a way to easily adjust fuel pressure. However, if your pump does not have an external/adjustable regulator, it likely uses a spring and ball to regulate fuel pressure. The spring and ball mechanism creates a seal when the pump is off, preventing fuel from leaking or moving in the lines. The spring is located in the main pump body, under the check ball.

The spring can be inconsistent, causing erratic fuel pressure readings or lower-than-expected readings. If you are experiencing erratic fuel pressure, you can try straightening out the spring and reinstalling it, or you may need to replace the spring altogether. You can contact FASS support to obtain a replacement spring.

If you are still experiencing lower pressure issues, you can try adding a washer to shim the spring and raise the pressure. It is important to ensure that you are not adding any additional restriction by using a washer with too small of an inner diameter. The washer should be added between the fitting and the spring, not between the spring and the ball.

Additionally, FASS uses a Buna ball, while Airdog uses a Viton ball. The Viton ball is made of stronger material and may provide better performance if you are experiencing issues with erratic or low fuel pressure.

Erratic fuel pressure may be caused by inconsistent springs

Erratic fuel pressure can be caused by a variety of factors, but one common issue is inconsistent springs. Technical springs are a vital component of fuel injection systems, which are themselves essential for modern internal combustion engines. These springs are designed to perform specific functions and have unique characteristics that set them apart from typical springs. They come in various shapes and sizes, including compression and torsion springs, and are made from high-quality materials.

In the context of FASS fuel pumps, the springs used in conjunction with a ball are responsible for regulating fuel pressure. Ideally, these springs should maintain a consistent pressure of 16-18 psi. However, the springs can sometimes be inconsistent, leading to erratic fuel pressure readings or lower-than-expected pressure. This inconsistency can be caused by various factors, such as manufacturing defects or wear and tear over time.

The impact of inconsistent springs on fuel pressure can be significant. Inaccurate fuel pressure can lead to incomplete combustion within the engine chamber, resulting in decreased engine efficiency and increased emissions. It can also cause issues such as engine misfires, rough idling, and reduced engine power.

To address erratic fuel pressure caused by inconsistent springs, there are a few potential solutions. One option is to straighten out the spring and reinstall it. Alternatively, you could replace the spring altogether with a new one provided by the pump manufacturer. In some cases, you may need to experiment with different types of balls used in conjunction with the spring, as different materials may provide varying results. Additionally, if you're experiencing lower-than-expected fuel pressure, you can try adding a washer to shim the spring and raise the pressure.

In summary, erratic fuel pressure in FASS fuel pumps can be caused by inconsistent springs, leading to a range of issues with the engine's performance. By understanding the role of technical springs in fuel injection systems and taking appropriate corrective actions, you can help ensure optimal engine performance, efficiency, and reliability.

A washer can be put in to shim the spring and raise the pressure

If you're experiencing lower pressure issues with your FASS fuel pump, you can put a washer in to shim the spring and raise the pressure. This is a solution that has worked for some users.

To do this, you will need to find a washer with the correct measurements. One user reported success with a 3/16" stainless washer, which increased the pressure by about 2 psi. Another user found a washer off a regular roofing screw useful; they peeled off the rubber, drilled the inside diameter needed, and achieved a pressure increase of about 2 psi.

It is important to note that the washer/shim should be added between the fitting and the spring, not between the spring and the ball. This adjustment can help raise the fuel pressure to the desired level, but it is crucial to ensure that you are not adding any additional restriction by using too small of an ID.

Additionally, some users have reported success with a combination of a Viton ball and a 17lb spring. The Viton ball is made of a stronger material, which can help address issues of erratic fuel pressure and lower-than-expected fuel pressure.

Before attempting any adjustments, it is recommended to consult with a professional or the FASS support team to ensure that you are making the correct modifications for your specific pump and to address any potential safety concerns.

The FASS pump may need to be running for the air separator/filter system to work

The spring can be inconsistent, leading to erratic or lower-than-expected fuel pressure readings. Inconsistent springs can be addressed by straightening or replacing them. FASS support can provide guidance and replacement parts. The type of ball used in the pump can also impact performance; FASS uses a Buna ball, while Airdog uses a Viton ball, which is made of stronger material. If you are experiencing lower pressure issues, you can put a washer in to shim the spring and raise the pressure.

It is important to note that too much lift pressure can cause issues, and that the FRPV (Fuel Regulator Pressure Valve) should not be active during normal use. The FASS pump should be calibrated from the factory to provide the correct volume and pressure, and adjustments may not be necessary. If you are experiencing issues with fuel pressure, it is recommended to consult with FASS customer support to determine the appropriate course of action.

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