2017-2025 Duramax 6.6L FASS Drop-In Series Diesel Fuel System

FASS Drop In Series Diesel Fuel System (2017–2025 GM Duramax L5P)

Part No: DIFSL5P1001

IMPORTANT NOTE

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

The FASS Drop In Series Fuel System is a true plug and play filtration upgrade designed specifically for the L5P Duramax. Modern diesel injection systems are extremely sensitive to fuel contamination and poor filtration can lead to premature wear and failure that costs thousands.

This system is engineered to remove over 99% of water from diesel fuel, eliminate entrained air/vapor, and filter debris down to 2 microns absolute, keeping your L5P fuel system protected and running clean.

It installs fast, requires no wiring, no cutting, and no tuning changes. Stock or modified, this system works without triggering codes or requiring tune adjustments.

Fitment

• 2017–2019 Crew Cab Short Bed L5P Duramax

• 2017–2025 Crew Cab Long Bed L5P Duramax

Notes:

• Installation on cab and chassis may require modifications

• Not compatible with fuel sump kits

• May not work with oversized aftermarket fuel tanks due to mounting space

Why This System Matters

Without proper filtration and air separation, modern high pressure injection systems are prone to excessive wear. The Drop In Series improves fuel quality by removing contaminants that hurt the fuel system and drivability.

Benefits may include:

• Cleaner fuel delivery

• Smoother running engine

• Sharper throttle response

• Improved MPG (results vary)

Key Features

• Retains full functionality of the factory water in fuel sensor

• Air separation built in (not just filtration)

• Increases fuel lubricity up to 10% by removing entrained air and vapor

• Extends the life of fuel injection system components

• Over 99% free + emulsified water separation with Extreme Water Separator (XWS) technology

• 2 micron absolute filtration

• 100% drop in plug and play design, no additional modifications required

• Retains the factory in-tank lift pump

• Works with factory plastic cap or billet filter cap

Extreme Water Separator Protection

FASS’s Extreme Water Separator (XWS) design helps protect your fuel system from major damage. If the separator reaches capacity, it acts as a safeguard to prevent contaminated fuel from continuing through the system.

FAQ

Will this system create excessive back pressure on the factory lift pump?
No. FASS engineering and testing reduced pressure drop compared to the OEM filtration system by optimizing internal port sizing and flow.

Why does it retain the OEM water separator setup?
Because the factory water in fuel sensor must remain on the dirty side of the separator to properly detect water before it reaches the clean side. This Drop In design keeps the water in fuel light and fuel heater working correctly.