FASS DIFSL5P2001 Drop-In Series Fuel System | 2020-2024 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax L5P

Features:

• Removes over 99% of water from fuel
• 2 micron absolute filtration rating
• Retains factory in-tank lift pump
• No cutting, wiring, or tuning required
• Works with factory or billet filter caps
• Installs in under an hour
• Maintains factory water-in-fuel sensor function
• Separates air and vapor from diesel fuel
• Improves throttle response and engine efficiency
• Plug-and-play installation with OEM-style fittings
• Compatible with factory fuel tank only

Drop-In Fuel System Upgrade for GM 6.6L Duramax

If you’re running a 2020–2024 L5P Duramax and want to protect your fuel system without diving into a complicated install, the FASS Drop-In Series Fuel System is a game-changer. Designed as a true plug-and-play upgrade, this system bolts into the factory water separator location and works with your truck’s OEM in-tank lift pump, not against it. That means no cutting, wiring, or tuning—just better filtration, improved drivability, and long-term protection for your injection system. What sets the Drop-In Series apart is its ability to remove over 99% of both free and emulsified water, thanks to FASS’s advanced Extreme Water Separator (XWS) technology. It's not just filtering large particles—it’s also eliminating the fine water droplets and entrained air that can wreak havoc on high-pressure fuel systems. By stripping air from the fuel, this system actually boosts fuel lubricity by up to 10%, which helps reduce wear on injectors and pumps. It’s a subtle but important upgrade, especially if you're towing heavy, pushing more power, or just want to avoid expensive repairs down the road.

High-Quality Construction & Design

One of the standout features is that the system retains the factory water-in-fuel sensor, something most aftermarket options can’t claim. That means you’ll still get accurate warnings if water is present in your diesel, and the OEM fuel heater continues to function just as it should—critical for cold-weather starts. FASS also engineered the system using Performance Radius Cuts (PRC) in the aluminum housing. These smooth, curved passages allow for better fuel flow and eliminate the sharp turns and restrictive fittings found in other setups, reducing backpressure and keeping the fuel flowing freely. This system is ideal for stock or modified trucks and is fully 50-state legal under CARB EO # D-713-3. It installs in less than an hour with basic tools and no special tuning, making it perfect for DIYers or anyone who wants an upgrade without the headache. Just make sure you’re working with a stock-style fuel tank, as this setup isn’t designed for oversized aftermarket tanks or cab-and-chassis applications without modification.

Fits: 2020, 2021, 2022, 2023, 2024 GM 6.6L Duramax

Application Notes:

• Installation of this kit on a cab and chassis may require modifications.
• Drop-In Fuel Systems are a plug-and-play filtration upgrade and are not compatible with FASS' Fuel Sump Kit.
• The Drop-In Series for the L5P Duramax was designed to be mounted in the factory water separator location and may not work with aftermarket fuel tanks that have a greater fuel capacity than the stock fuel tank. You must verify that you have adequate space to mount the Drop-In Series System if you have an aftermarket fuel tank.
• THIS IS NOT A LIFT PUMP! This is an air separation/filtration system that utilizes your factory lift pump.

Install Instructions