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

If you're looking to adjust the fuel pump pressure on your FASS pump, you may have to get creative. FASS and Airdog pumps typically do not come with a way to easily adjust fuel pressure. One option is to adjust the spring that regulates fuel pressure. This can be done by stretching the existing spring or by purchasing a new spring with a higher psi rating. Another option is to adjust the pressure regulator on the pump, if it has one. This is usually a screw that can be turned to increase or decrease the pressure. It's important to note that running higher fuel pressure won't gain you more horsepower, and too much pressure can cause issues like the truck starting to lope. If you're having trouble getting the desired pressure from your FASS pump, you may need to continue diagnosing for issues elsewhere in the fuel supply system or with the pump itself.

Replacing the spring

To replace the spring, you will need to first locate the spring. Typically, the spring is located behind the return fitting that sends excess fuel back to the fill neck of the tank. You will need to remove the hose or fitting connected to the "air/vapor return to the tank" to access the spring.

Once you have located the spring, you can either straighten it out and reinstall it or replace it with a new one. If you choose to replace the spring, you can purchase a new one from the pump manufacturer or a local hardware store. Be sure to get the correct spring for your specific pump model.

When removing the old spring, be careful not to drop the rubber ball that sits behind the spring. This ball creates a seal when the pump is off, preventing fuel from leaking or moving in the lines. You may also want to inspect the ball for any indentations or damage, as this can cause erratic fuel pressure.

If you choose to straighten and reinstall the old spring, be sure to do so carefully to avoid any kinks or twists, which can cause erratic fuel pressure.

In some cases, you may need to adjust the spring tension to achieve the desired fuel pressure. This can be done by stretching the spring or adding a washer to shim the spring and raise the pressure. However, it is important to note that increasing the fuel pressure too much can cause issues with the engine, so it is best to consult with a professional or the pump manufacturer before making any adjustments.

Installing a pump pressure gauge

Step 1: Purchase the Correct Gauge

Before you begin the installation, it is important to purchase a suitable fuel pressure gauge. Make sure to select a gauge that is compatible with your FASS fuel pump and has the appropriate fittings and adapters. You can find these gauges at most automotive stores or online.

Step 2: Identify the Location

The location for installing the gauge will depend on your preference and the layout of your engine bay. You can choose to install the gauge directly on the FASS fuel pump or along the fuel line. Some common locations include the fuel filter housing, the fuel hat, or the bleeder screw on the filter head.

Step 3: Prepare the Installation Site

If you're installing the gauge on the FASS fuel pump, locate the existing port on the pump. This port is usually found in the fuel hat or where the line connects to the VP44. You can also choose to drill and tap into the fuel line, ensuring you use the appropriate fittings and adapters.

Step 4: Install the Gauge

Once you've identified the location, carefully install the gauge according to the manufacturer's instructions. If you're using a mechanical gauge, you may need to mount it outside the cab. Ensure that the gauge is securely attached and all connections are tight to prevent fuel leaks.

Step 5: Test the Installation

After installing the gauge, start the engine and allow it to idle. Observe the fuel pressure reading on the gauge and ensure that it is within the normal range for your vehicle. You may need to refer to your vehicle's manual or consult a mechanic to determine the optimal fuel pressure.

Step 6: Adjust the Pressure (if needed)

If the fuel pressure reading is not within the desired range, you may need to adjust the pressure. This can be done by stretching or replacing the spring in the FASS fuel pump. You can also add a washer to shim the spring and raise the pressure. It is recommended to consult a professional or the FASS support team for guidance on adjusting the fuel pressure.

By following these steps, you can successfully install a pump pressure gauge on your FASS fuel pump. Remember to work carefully and refer to the specific instructions provided by the gauge and pump manufacturers to ensure a safe and proper installation.

Adjusting the psi

To adjust the psi on a FASS fuel pump, you will need to determine the model of your pump, as different models have different psi adjustment methods and requirements.

For example, the Grey Titanium Series FASS pumps come with a 55psi spring in the return port. To adjust the psi on these pumps, you can replace the spring with a 75psi spring to increase the pressure.

On the other hand, the Black Titanium Signature Series FASS pumps use either a spring and ball or a spring and aluminium poppet to regulate fuel pressure. These pumps should produce around 70psi out of the box, so you may not need to adjust the psi. However, if you are having issues with fuel pressure, you can try using the pinch test to determine if the regulator is causing the problem.

For FASS pumps without an external/adjustable regulator, the pump likely uses a spring and ball to regulate fuel pressure. In this case, you can try straightening or replacing the spring to adjust the psi. Additionally, you can try using a stronger ball material, such as Viton, to create a better seal and improve fuel pressure.

It is important to note that adjusting the psi on your FASS fuel pump may not result in increased horsepower. In fact, higher psi can lead to a decrease in the pump's flow rate. Therefore, it is recommended to consult with a professional or FASS support to determine the appropriate psi for your specific pump and vehicle.

Troubleshooting low fuel pressure

• Dirty fuel filter or clogged pump inlet strainer: Check if the fuel filter is dirty or clogged, as this can restrict fuel flow and result in low pressure.
• Weak pump: A weak or faulty fuel pump may not be able to generate sufficient fuel pressure.
• Incorrect tank venting or restricted fuel lines: Ensure the fuel tank is vented correctly and there are no restrictions in the fuel lines, as these can cause low pressure.
• Low voltage to the pump: Insufficient voltage can prevent the pump from spinning fast enough to build up normal pressure.
• Faulty electrical control: A problem with the electrical control system, such as a faulty fuel pump driver module, can lead to low fuel pressure.
• Fuel leaks: Leaks in the fuel system, such as a faulty diaphragm or seals in the fuel pressure regulator, can result in low fuel pressure and potential safety hazards.
• Clogged fuel injectors: Dirty or clogged fuel injectors can restrict fuel flow and cause low pressure.
• Faulty pressure regulator: A faulty fuel pressure regulator may not be able to maintain the correct fuel pressure, leading to engine performance issues.
• Incorrect spring tension: Inconsistent spring tension can cause erratic or lower-than-expected fuel pressure readings.
• Incorrect ball material: Using the wrong type of ball (Buna vs Viton) in the fuel system can lead to erratic fuel pressures and potential damage to the spring.

It is important to diagnose and address these issues to ensure the fuel system functions optimally and to prevent further complications.

Understanding the role of the regulator

The regulator is a critical component in the FASS fuel pump system, responsible for maintaining stable fuel pressure. It ensures that the fuel pressure remains within an optimal range, typically between 16-18 psi, to prevent erratic fuel pressure readings or lower-than-expected fuel pressures.

The regulator works in conjunction with a spring and a ball, either Buna or Viton, to create a seal when the pump is turned off. This prevents fuel from leaking or moving in the lines when the pump is inactive. However, issues with the regulator can lead to erratic fuel pressure, which may require adjustments or replacements.

In some cases, the spring inside the regulator may become twisted or stretched, affecting fuel pressure. Straightening or replacing the spring can resolve this issue. Additionally, the ball may indent the spring, and using a stronger material, such as a Viton ball, can provide a more durable solution.

Furthermore, a washer can be placed between the fitting and the spring (not between the spring and the ball) to shim the spring and raise the fuel pressure. This adjustment should only be made if you are experiencing lower pressure issues and should be done carefully to avoid adding restriction to the fuel flow.

It is important to note that FASS and AirDog pumps have internal regulators that may need adjustments or rebuilding if they develop leaks over time. These pumps typically come pre-set at 55 psi, and adjustments may be necessary to achieve the desired fuel pressure at the engine.

Frequently asked questions