FASS Drop-In Series Fuel System – for 2017 to 2025 GMC/Chevrolet, Duramax 6.6L

THIS IS NOT A LIFT PUMP! This is an air separation/filtration system that utilizes your factory in-tank lift pump.

The DIFSL5P1001 Fits: 2017-2025 Crew Cab Long Bed L5P Duramax
The DIFSL5P1001 Fits: 2017-2019 Crew Cab Short Bed L5P Duramax
The DIFSL5P2001 Fits: 2020-2025 Crew Cab Short Bed L5P Duramax

Note: Installation on cab and chassis may require modifications. Drop-In Fuel Systems are plug and play filtration upgrades and not compatible with Fuel Sump Kits. System retains the OEM fuel pump. ATTENTION! The Drop-In Series System for the L5P Duramax was designed to mount in the OEM water separator location and may not work with aftermarket fuel tanks that have greater fuel capacity than the stock tank. YOU MUST VERIFY THAT THERE IS ADEQUATE SPACE TO MOUNT THE DROP-IN SERIES FASS SYSTEM IF YOU HAVE AN AFTERMARKET FUEL TANK!!

The FASS Drop-In Series Diesel Fuel System is engineered to be the most effective filtration solution for the 6.6L Duramax. Backed by a limited lifetime warranty, it protects your 6.6L Duramax from the damage caused by air, vapor, water, and debris in your diesel fuel.

Without proper fuel filtration, modern diesel injection systems are prone to excessive wear that can cost thousands. By removing over 99% of the water from your fuel along with air, vapor, and debris down to 2 microns absolute, the Drop-In Series WILL TRIPLE the life of your injection system.

The FASS Drop-In Series System for the L5P Duramax replaces the plastic OEM single filter housing with a 6061-T6 billet aluminum, American-made dual filter housing. This system utilizes the OEM water separator element in conjunction with our 2 micron Extreme Water Separator. Utilizing the OEM water separator element allows the water-in-fuel sensor to operate correctly, notifying you before the water reaches the clean side of the fuel filter element. Many other systems on the market utilize a spin-on water separator that places the WIF sensor on the clean side of the filter. By the time your WIF light is triggered, it’s too late! Our Extreme Water Separator provides the final particulate and water filtration, filtering particulates down to 2 microns and removing over 99% of free and emulsified water. OEM filtration provides a 5 micron filtration rating, allowing the larger particulates to pass through to your injection system.

Eliminating these contaminants optimizes MPG, restores horsepower and sharpens throttle response while improving the operational balance of your engine through consistent fuel delivery timing. And it installs in as little as an hour, a true plug-and-play system with no cutting, wiring or additional modifications, delivering a real return on investment by cutting maintenance costs and protecting the most expensive components on your truck.

Our industry-leading water removal is reinforced by the design of the Extreme Water Separator (XWS). If the XWS ever reaches capacity, it acts as a dam and shuts down fuel flow, a mechanical shutdown that stops a bad tank of fuel from destroying your injection system.

Reliability, Simplicity, Protection

• Supports Stock & Modified Duramax: Plenty of fuel for stock and modified GMCs and Chevrolets.
• Injector Protection: WILL TRIPLE the life of your fuel injection system.
• FASS Filtration: Optimizes combustion, restores horsepower, and maximizes MPG.
• Limited Lifetime Warranty: Register your FASS system for coverage.

Advanced Filtration Technology

• Water Separation: Extreme Water Separation Technology, 3rd-party proven to eliminate over 99% of free and emulsified water.
• Air/Vapor Removal: Patented process eliminates entrained air/vapor that damage injection systems.
• 2 Micron Absolute Microglass Filtration: Removes smaller debris than OEM filters.

Key Benefits

• Improves Reliability: WILL TRIPLE the injection system life.
• Maximized Horsepower: Improved fuel atomization and restored timing.
• Optimized MPG: More efficient and complete combustion.
• Peace of Mind: Extreme Water Separator acts as a fail-safe against a bad tank of fuel.
• Cold Weather Confidence: Reliable starts and operation in harsh climates, especially when paired with the FASS Drop-In Fuel Heater Kit.
• Cleaner Operation: Reduced DPF regenerations and soot output through improved combustion.
• Improves Fuel Lubricity: At least 10% improvement by removing entrained air/vapor.
• Lower Cost of Ownership: Reduced maintenance and fewer injection-system repairs.

Key Features

• The only Drop-In 6.6L Duramax filtration system that retains full functionality of the OEM water-in-fuel light.
• The only Drop-In filtration system in the light-duty market with air separation.
• Increases fuel lubricity by at least 10%.
• WILL TRIPLE the life of fuel injection components.
• 100% drop-in installation; no modifications needed.
• Retains the factory in-tank lift pump.
• 6061-T6 billet aluminum, American-made dual filter housing replaces the plastic OEM housing.
• Runs the OEM water separator element in series with the FASS Extreme Water Separator.
• Performance Radius Cuts (PRC): Smoother internal fuel flow.
• 2 micron absolute filtration rating: Captures finer debris than OEM.
• Removes over 99% of free and emulsified water: 3rd party verified.
• Patented air/vapor removal process.
• Electric heater options available for cold weather reliability.
• Limited Lifetime Warranty (with registration).

What’s Included In The DIFSL5P FASS Drop-In Series:

• (1) FASS Drop-In Series Air Separation/Filtration System
• (1) FASS XWS3002 Extreme Water Separator
• (1) Installation Kit Including Fittings, Bracketry, and Hardware

Recommended Add-Ons

• FASS Drop-In Series Electric Heater Probe Kit: Cold-weather gelling protection.
• FASS XWS3002 Extreme Water Separator: Replacement element.

Why Choose FASS?

See more here at Why FASS or review our craftsmanship standards at FASS Craftsmanship

At FASS, we don’t rush products to market, we “Strive for perfection & settle for excellence”. That’s why our systems have a failure rate of less than .5%, and why diesel owners across the country trust us to protect their investments. Whether you’re daily driving your Duramax-powered GMC/Chevrolet or building horsepower, the FASS Drop-In Series Fuel System gives you peace of mind and performance you can feel. Register your system with FASS to activate the limited lifetime warranty.

Vehicle Fitment by Year

• 2017 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2017 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2017 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2017 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2018 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2018 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2018 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2018 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2019 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2019 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2019 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2019 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2020 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2020 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2020 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2020 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2021 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2021 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2021 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2021 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2022 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2022 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2022 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2022 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2023 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2023 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2023 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2023 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2024 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2024 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2024 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2024 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2025 GMC Sierra 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2025 GMC Sierra 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)
• 2025 Chevrolet Silverado 2500HD/3500HD Crew Cab Short Bed – 6.6L Duramax (L5P)
• 2025 Chevrolet Silverado 2500HD/3500HD Crew Cab Long Bed – 6.6L Duramax (L5P)