FASS

What Is FASS?

FASS stands for Fuel Air Separation System. Based in Marthasville, Missouri, FASS Diesel Fuel Systems has spent over two decades engineering, manufacturing, and assembling diesel fuel solutions entirely in the USA. The name perfectly describes what the brand does: combine a high-performance diesel fuel lift pump with advanced filtration and a patented air-and-vapor removal process, all in one integrated system.

The Science Behind FASS Fuel Systems

Modern high-pressure diesel injection systems are remarkably precise — and remarkably sensitive. Air and vapor entrained in diesel fuel can disrupt combustion, reduce power, shorten injector life, and hurt fuel economy. FASS systems tackle this problem at the source. Their patented fuel air separation technology removes dissolved air and vapor from the fuel before it ever reaches the injection pump, delivering cleaner, denser fuel that burns more completely. The result is improved horsepower, torque, and efficiency, along with meaningful protection for expensive injection components.

FASS fuel lift pumps are available in vehicle-specific configurations for Dodge RAM with 5.9L or 6.7L Cummins engines, Ford trucks with Powerstroke engines, Chevrolet and GMC pickups equipped with Duramax engines, and even Class 8 semi-truck applications. Flow rates span from 100 GPH up to 290 GPH, with options to suit everything from a stock daily driver to a 1,500+ horsepower competition build.

A Full Lineup for Every Diesel Owner

FASS organizes their product lineup into several distinct series to match different budgets and build levels. The flagship Titanium Signature Series is their most popular, integrating a frame-mounted lift pump, particulate filtration down to 2–3 microns, and a water separator in a single assembly. The Drop-In Series is engineered as a true bolt-in upgrade — using the factory in-tank lift pump while adding FASS-grade filtration — and can be installed in under an hour. The Adjustable Fuel Pump and Direct Replacement Pump (DRP) lines round out the catalog, serving high-performance and direct-replacement applications respectively.

Beyond the core pump systems, FASS offers a comprehensive ecosystem of supporting products. Their mechanical fuel pumps — including the popular Direct Replacement Pump — are engineered to replace the failure-prone factory block-mounted pumps found on early Cummins-powered Dodge trucks. For diesel owners in cold climates, FASS fuel injection fuel heaters prevent diesel gelling and keep fuel flowing even in extreme temperatures. Completing the system, FASS fuel water separator filters are purpose-built for FASS pumps, with their Extreme Water Separator (XWS) design proven by third-party testing to exceed 99% water removal efficiency.

Built in the USA, Backed by a Lifetime Warranty

FASS manufactures its products using materials sourced within the United States and backs its Titanium series fuel systems with a limited lifetime warranty — a reflection of the brand's confidence in its own engineering. Their product range serves not just diesel pickup owners but also RV operators, agricultural equipment users, marine applications, and extreme competition builds, making FASS one of the most versatile names in diesel fuel system technology.