L5P Duramax Drop-In Series Diesel Fuel System | FASS DIFSL5P1001

Protect an L5P injection system without adding a second lift pump. The FASS DIFSL5P1001 Drop-In Series is an air-separation and filtration system that mounts in the factory water-separator location and still uses the OEM in-tank pump. It replaces the plastic single-filter housing with a 6061-T6 billet aluminum dual-filter housing, keeps the factory water-in-fuel sensor working, and adds FASS Extreme Water Separator filtration down to 2 microns. That combination removes water, air, and debris before they reach the high-pressure pump and injectors. CARB Executive Order D-713-3.

Key features

• Drop-in filtration and air-separation system, not a lift pump
• Retains the factory in-tank lift pump
• Only drop-in L5P system that keeps full water-in-fuel sensor function
• Only drop-in L5P system with air separation
• Over 99% free and emulsified water separation
• 2-micron absolute filtration with XWS3002 Extreme Water Separator
• Increases fuel lubricity by removing entrained air and vapor
• 6061-T6 billet aluminum dual-filter housing made in the USA
• Performance Radius Cuts for smoother internal flow
• Works with the factory plastic cap or a FASS billet filter cap
• No cutting, welding, wiring, or tuning required on listed trucks
• CARB EO D-713-3
• Limited lifetime warranty with product registration

Fitment

• 2017–2019 Chevrolet Silverado / GMC Sierra 2500HD / 3500HD 6.6L Duramax L5P crew cab short bed
• 2017–2025 Chevrolet Silverado / GMC Sierra 2500HD / 3500HD 6.6L Duramax L5P crew cab long bed

2020–2025 crew cab short bed trucks use FASS DIFSL5P2001 instead. Cab-and-chassis installs may need modifications. Not compatible with FASS fuel sump kits or oversized aftermarket tanks that do not match the factory tank location. CARB EO D-713-3 lists 2017–2023 GM 6.6L applications.

What’s in the box

• FASS Drop-In Series air-separation / filtration housing
• FASS XWS3002 Extreme Water Separator
• Installation kit with fittings, bracketry, hose, and hardware
• Instructions

Factory water-separator element is reused so the OEM water-in-fuel sensor stays on the dirty side of the system.

Notes & specs

• Brand/part number: FASS Fuel Systems DIFSL5P1001
• UPC: 850044137268
• Engine: 6.6L Duramax L5P
• Type: drop-in filtration / air separation (not a lift pump)
• Filtration: 2 micron absolute
• Water separation: over 99%
• Replacement filter: FASS XWS3002
• Compatible heater: Drop-In Series heater kit only
• CARB EO: D-713-3
• Install time: about 1 hour on listed crew-cab trucks
• Warranty: limited lifetime with registration

This system filters fuel. It does not add pump volume like a Titanium or Titanium Signature Series lift pump. Register the kit with FASS to activate the lifetime coverage. If you want better water, air, and dirt control on a 2017–2019 short-bed or 2017–2025 long-bed L5P without changing the factory lift pump, the FASS DIFSL5P1001 Drop-In Series is the plug-and-play filtration upgrade built for that truck.