Diesel performance enthusiasts often look for ways to maximize the power and longevity of their engines. One of the most critical components in any high-end custom truck build is the fuel delivery system. Specifically, the Fuel Air Separation System, commonly known as FASS, has become a standard for those seeking to push their vehicles to the limit while maintaining reliability. This guide explores how these systems function and why they are the cornerstone of top-tier diesel builds.
When you see a custom diesel truck at a show or on the track, it is likely equipped with an aftermarket fuel system. These systems are designed to solve a fundamental problem in diesel engineering: the presence of air and vapor in the fuel lines. By removing these impurities, owners can achieve better throttle response, increased fuel economy, and a significant boost in engine life. Understanding how to integrate these systems into a build is essential for anyone looking to improve their diesel vehicle’s performance.
Understanding the Role of Fuel Air Separation
In a standard diesel engine, the fuel is pulled from the tank and sent to the injectors. During this process, mechanical agitation and temperature changes can cause air bubbles and vapor to form. When these bubbles reach the fuel injectors, they cause a variety of issues, including inconsistent combustion, increased noise, and premature wear on expensive components. A FASS system acts as a secondary filtration and delivery hub that purifies the fuel before it ever reaches the engine.
The system works by using centrifugal force to separate the heavier fuel from the lighter air and vapor. The purified fuel is then sent to the engine under consistent pressure, while the air and vapor are returned to the fuel tank. This process, often referred to as “fuel polishing,” ensures that the engine receives the highest quality fuel possible. For custom builds that utilize high-flow injectors and performance tuning, this steady supply of clean fuel is not just an upgrade; it is a necessity.
Key Benefits for Custom Diesel Builds
Integrating a performance fuel system into a custom build offers several tangible benefits that go beyond simple horsepower gains. While power is a major factor, the practical improvements to the vehicle’s daily operation are equally important for most owners.
- Increased Injector Life: Fuel injectors are among the most expensive parts of a diesel engine. Air bubbles can cause cavitation, which erodes the internal surfaces of the injector. By removing air, the system protects this investment.
- Consistent Power Delivery: Without air in the lines, the engine’s timing remains precise. This leads to smoother acceleration and more predictable power when towing or racing.
- Better Cold Weather Starts: Performance fuel systems often include heating elements or improved filtration that helps prevent fuel gelling in cold climates.
- Improved Fuel Economy: While it may seem counterintuitive for a performance part, a more efficient combustion process often leads to a slight increase in miles per gallon.
Popular Vehicle Builds Featuring FASS Systems
Different diesel platforms require different approaches when it comes to fuel delivery. Whether you are working with a Cummins, Duramax, or Powerstroke engine, the integration of a FASS system is a common thread among high-performance builds.
The Cummins Performance Build
The Dodge Ram Cummins platform is legendary for its torque and durability. However, the factory lift pumps on many older models are known to be a weak point. Custom Cummins builds often feature a FASS Titanium Signature Series pump to ensure the high-pressure injection pump (like the P7100 or CP3) is never starved for fuel. In builds pushing over 600 horsepower, this system is essential to prevent the engine from “leaning out” under heavy load.
The Duramax Lift Pump Solution
Unlike other diesel engines, many Chevy and GMC Duramax trucks do not come with a factory lift pump. The injection pump is forced to pull fuel all the way from the tank, creating a vacuum that can lead to air ingress. A popular modification for Duramax owners is to install a FASS system to provide positive pressure to the engine. This modification alone can significantly improve the reliability of the CP3 pump and provide a cleaner look to the engine bay by relocating the fuel filters.
The Powerstroke Reliability Build
Ford Powerstroke engines, particularly the 6.0L and 6.7L models, benefit greatly from improved filtration. The 6.7L Powerstroke is capable of immense power, but its fuel system is sensitive to contaminants. Custom builds on this platform often use a FASS system to provide 2-micron filtration, which is much finer than the factory standards. This ensures that the high-pressure fuel rails remain free of debris, preventing costly repairs down the road.
Planning Your Custom Build
If you are planning to build a custom diesel truck, the fuel system should be one of the first upgrades you consider. It provides the foundation for all other modifications. If you install large injectors or a bigger turbocharger without upgrading the fuel delivery, you will likely encounter performance bottlenecks or engine damage.
Choosing the Right Flow Rate
FASS systems come in various flow rates, typically measured in gallons per hour (GPH). For a daily driver with mild tuning, a 100 GPH or 110 GPH system is usually sufficient. However, for dedicated race trucks or heavy-duty towing rigs, a 165 GPH or even a 250 GPH system may be required. It is important to match the flow rate to your target horsepower to ensure the engine always has an adequate supply of fuel.
Installation Considerations
Most performance fuel systems are designed to be mounted to the vehicle’s frame rail. This keeps the pump and filters protected and makes them easy to access for maintenance. When installing the system on a custom build, pay close attention to the routing of the fuel lines. Avoid areas with excessive heat, such as the exhaust system, and ensure the lines are secured to prevent rubbing or vibration.
Maintenance for Long-Term Reliability
Once a FASS system is installed, it requires regular maintenance to keep the truck running at its peak. This primarily involves changing the fuel filter and the water separator. Most experts recommend changing these filters every 12,000 to 15,000 miles, or sooner if you frequently use low-quality fuel.
Monitoring your fuel pressure is also a vital part of maintenance. Many custom builds include a fuel pressure gauge in the cab. A sudden drop in pressure can indicate that the filters are clogged or that the pump needs attention. Staying proactive with these small tasks will ensure that your custom diesel ride remains reliable for hundreds of thousands of miles.
Conclusion
Building a high-performance diesel truck is a rewarding process that requires careful selection of components. By prioritizing a high-quality fuel air separation system, you create a stable foundation for power, efficiency, and longevity. Whether you are aiming for a show-quality street truck or a rugged workhorse, ensuring your engine receives pure, air-free fuel is the best way to protect your investment. To learn more about optimizing your vehicle, explore our other articles on diesel engine maintenance and performance upgrades.