FASS Drop-In Fuel System | 2003–2007 RAM 2500/3500 Cummins
$479.00
FASS Drop-In Fuel System | 2003–2007 RAM 2500/3500 Cummins
FASS Drop-In Series Diesel Fuel System: Fits 2003–2007 RAM 2500/3500, 5.9L Cummins
The DIFSRAM2001 Fits: 2003-2007 RAM 2500 & RAM 3500 5.9L Cummins (WITH AN IN-TANK LIFT PUMP). 2003-2004.5 trucks MUST have been retrofitted with an in-tank lift pump in order to utilize this product.
Please Note: THIS IS NOT A LIFT PUMP! This is an air separation/filtration system that utilizes your factory in-tank lift pump.
Not compatible with the FASS Fuel Sump Kit. May not fit aftermarket high-capacity fuel tanks; verify clearance before ordering.
Please Note: 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 our Fuel Sump Kit. The system mounts in the factory location and may not fit aftermarket high-capacity fuel tanks; verify clearance before ordering. No additional items are needed for installation. This plug-and-play filtration system retains the Cummins OEM fuel pump.
FASS Drop-In Technology: The FASS Drop-In Series Diesel Fuel System is engineered to be the most cost-effective and easiest solution for removing air/vapor from diesel fuel in your diesel fuel injection system. By implementing the extreme water separator (XWS3002) filter our system will provide 2 microns absolute filtration.
Removing entrained air and vapor, Extreme Water Separation, and 2 micron absolute filtration with a Micro-Glass filter element all work together in the FASS Drop-In for Ram to optimize fuel efficiency, restore horsepower, and improve performance across the entire fuel system and engine. And that’s only scratching the surface of the benefits FASS brings to your Cummins.”
Imagine being able to improve MPG (fuel efficiency), horsepower, increase fuel injection system life, truly balance the engine (smoother operation) with other benefits listed below with an installation time in about 1 hour!
FASS Drop-In Series System Features
Remove the entrained air and vapor from your diesel fuel and a chain reaction follows.
Tap any feature to see each link in it.
Patented Air & Vapor Separation - “TIMES” 2
Increases Lubricity to Fuel Injection Components
At least a 10% gain in fuel lubricity under stationary conditions — and that’s the floor. Agitation begins the moment the engine does, and vehicle motion compounds it. Restricting filters, higher elevation, heated fuel, and lower fuel levels drive air/vapor higher yet. The field calls it “fuel starvation.” Physics calls it entrained air/vapor. Strip it out, and lubricity gains travel well north of 10%.
FASS will “TRIPLE” the life of your fuel injection system — and keep thousands of dollars in your pocket over the long haul.
Optimizes Fuel Efficiency / Horsepower
Because air and vapor are compressible and fuel is not, they delay fuel entry into the cylinder. Combustion starts late, the burn rate suffers, and the power stroke produces fewer BTUs than it should.
From the Field — FASS optimizes fuel efficiency.
- Customers consistently reporting gains of 6-11%, coupled with horsepower gains.
- Customer consistently report the following:
- Truck Only: 1 – 2.5mpg increase
- Loaded: .5 – 1.5mpg increase
True Engine Balancing — Smoother & Quieter Operation
Air/vapor delays fuel delivery, and it does so inconsistently and unpredictably — throwing the engine out of time. Strip it out, and every cylinder hits its true contribution on every power stroke.
Customers hear it first, then feel it — in the mirrors, in the steering wheel. The engine runs smoother, and less vibration reaches the cab. Less vibration means less stress, and less stress means a longer life.
Consistent Engine Performance with HP Gains
Diesel engine output depends on precise fuel injection timing, and air/vapor undermines that precision.
Your Cummins engine was rated in a “Test Cell” — clean, non-agitated fuel, positive flow, roughly 10% air in solution. FASS delivers those same conditions in the “Real World” with the air removed, edging performance just past the “Test Cell” rating.
Reduces: Regens, Soot/Emissions, EGT’s (Turbo Temps), Water/Oil Temps, Oil Consumption
Shift the fuel timing and you shift the BTUs produced by every power stroke. That single shift ripples outward: how much soot is created, how and when combustion occurs, and how fast heat exits the cylinder as valve and combustion timing drift apart. Even ring seating depends on it.
Every one of these benefits leads to the same place: COST. FASS reduces maintenance spending across the board, and while that may sound too good to be true, the physics and the customer reports say otherwise.
- Soot/Emissions: down 18-76.8% — plus reductions across CO, CO₂, and Oxides of Nitrogen.
- Regens: Many customers report their regen frequency drops by about half.
- EGT’s (Turbo Temps): typical stock applications 50-100°F; modified applications 150°F and up, over 200°F.
- Water/Oil Temps: reported 15-25°F.
- Oil Consumption: customers have reported reduced oil consumption.
Peace of Mind — “Real” Water Separation
Higher Volume Water Conditions
Third-party proven to remove over 99% of water. In a major contamination event, traditional and OEM cellulose filters pass water straight through to the fuel injection system — and the damage is catastrophic. The FASS Extreme Water Separator dams the flow instead, stopping that water cold.
The benefit, simply put: competitors’ filters fill with water, pass that water to the fuel injection system, and you’re looking at catastrophic damage and downtime.
Conventional cellulose filters (OEM/direct competitors) — costly when it counts:- Repair or replace the fuel system — are the parts even available?
- Replace filters and replace fuel — more shop time, more cost.
- Vehicle sits idle, producing nothing — and where are you, loaded or on vacation?
- No fuel system repair or replacement.
- Replace filters and service fuel with FASS filters — that’s it.
- Vehicle stays working.
2-Micron Absolute Microglass Filter — 30,000-Mile / 5,000-Gallon Life Expectancy
Competitors and OEMs use cheap cellulose filters with large micron ratings. Ours is 2-micron absolute microglass — 400% more efficient and much higher quality, rated at 1,500 GPH.
To match a cellulose filter to the capability/efficiency of a microglass element you will need a filter four times the size of filter. Our filter has four times the effective filtration, and catches finer debris along the way.
Cold Weather & Fuel Conditioning
Extreme Cold Weather Operations
Pair our high-efficiency Micro-Glass fuel filter, rated at 1,500 GPH, with the optional FASS Heater Kit for your climate, and leave traditional OEM gelling and cold-start problems behind.
Drop-In + FASS Heater Kit. This set up takes 2nd only to it’s brother the FASS Titanium Series PLUS Fuel System.
Let’s take it one step further: want to preheat your FASS System with your phone from the warmth of your home? If you’re within about 250 feet, just add FASS Connect to your FASS Heater Kit.
Dependable starts and smooth operation in extreme cold, with no extra modifications. Install the FASS Drop-In System with heater kit about an hour and head into winter with confidence. To Install the FASS Drop-In System with heater kit and head into winter with confidence.
MASS Flow Return (MFR)
FASS keeps positive pressure on the fuel going to your engine and sends the fuel your engine doesn’t use back to the tank. That returning fuel has already passed through the FASS filters, with air/vapor, water, and debris removed, so the fuel in your tank is constantly moving and being cleaned
Every pass makes your fuel cleaner. Your tank holds progressively "Polished" fuel, and your fuel injection system always sees the cleanest fuel possible.
What’s Included In The DIFSRAMX001
- (1) FASS Drop-In Series Air Separation/Filtration System
- (1) FASS XWS3002XL Extreme Water Separator
- (1) FASS CWS1010 Coalescing Water Separator
- (1) Installation Kit Including all necessary Fittings, Bracketry and Hardware
Why Choose FASS?
OEM filtration was validated in a "Test Cell". It was never designed to deliver that same Performance, Productivity, and Protection in the "Real World" working conditions. That's why the people who build this GREAT country turn to FASS.
Brad Ekstam, Founder & President
See more here at 
or review our craftsmanship standards at 
At FASS, we don’t rush products to market, we are “Striving for Perfection Settling for Excellence”. That’s why our systems have a failure rate of less than 0.5%, and why diesel owners across the country trust us to protect their investments. Whether you’re daily driving your diesel truck 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
Fits 2003–2007 Dodge Ram 2500/3500 5.9L Cummins.
| Years | Make | Model | Engine |
|---|---|---|---|
| 2003–2007 | Dodge Ram | 2500 / 3500 | 5.9L Cummins |
| Weight | 28 lbs |
|---|---|
| Dimensions | 18 × 14 × 28 in |