FASS

What Is FASS Diesel Fuel Systems?

FASS stands for Fuel Air Separation System — and that name says it all. FASS Diesel Fuel Systems, headquartered in Marthasville, Missouri, has spent over two decades engineering, manufacturing, and assembling diesel fuel solutions entirely in the USA. The brand was built on a single, powerful idea: modern high-pressure diesel injection systems are extraordinarily precise, and even small amounts of entrained air, vapor, water, or microscopic debris can rob an engine of power, hurt fuel economy, and dramatically shorten injector life. FASS exists to eliminate those threats before they reach your engine.

How FASS Systems Work

At the heart of every FASS system is a combination of three functions working together: air and vapor separation, advanced particulate filtration, and water removal. By addressing all three in a single integrated unit, FASS delivers clean, pressurized fuel to the injection system on every stroke. Their systems filter contaminants down to 2 microns and remove over 99% of water from the fuel stream — far beyond what stock filters can achieve. The result is protection that can, according to FASS, dramatically extend the service life of expensive injectors and injection pumps.

FASS constructs its systems from 6061 T6 aircraft- and marine-grade aluminum and incorporates several proprietary technologies, including FASS Silencing Technology (FST), Performance Radius Cuts (PRC), and Mass Flow Return (MFR). These innovations set FASS apart in both build quality and long-term durability.

FASS Product Lines

The brand's Fuel Lift Pump lineup is its core offering and its biggest claim to fame. The flagship Titanium Signature Series integrates a frame-mounted lift pump, advanced particulate filtration, and a water separator in one assembly, with flow ratings ranging from 100 to 290 gallons per hour to suit everything from a stock pickup to a 900-horsepower competition build. For trucks that don't need a full frame-mounted system, the Drop-In Series provides a bolt-in upgrade using the factory in-tank housing, while the Adjustable Fuel Pump and Direct Replacement Pump (DRP) lines serve high-performance and direct-replacement applications.

Beyond the core lift pump systems, FASS offers an ecosystem of supporting products. Their Fuel Pump options — including the popular DRP — are engineered to replace the failure-prone factory block-mounted pumps found on early Cummins-powered Dodge trucks. For diesel owners looking for a complete, all-in-one solution, the Vertical Fuel Conditioning Module condenses FASS's proven filtration and air-separation technology into a compact, vertically oriented package ideal for space-constrained installations.

Clean fuel means nothing if it's contaminated with water — especially in demanding work-truck and towing applications. FASS Fuel Water Separator Filters, including their Extreme Water Separator (XWS), are rated to 2 microns absolute and serve as a critical fail-safe against water-laden fuel. And for diesel owners in cold climates, FASS Fuel Injection Fuel Heaters are thermostatically controlled to automatically activate when fuel temperatures drop near the gelling threshold, keeping fuel flowing reliably through the harshest winters.

Who FASS Is Built For

FASS builds vehicle-specific systems for Dodge/RAM with Cummins engines, Ford with Powerstroke engines, Chevrolet and GMC with Duramax engines, and Class 8 commercial semi-trucks. Whether you're hauling heavy loads, running high-horsepower modifications, or simply want to protect a long-term daily driver, FASS has a system engineered for the job — and backs it with a lifetime warranty on their Titanium series products.