PureFlow AirDog II-5G 98.5-04 Dodge 24V 5.9L Cummins (w/o Pump) DF-100-5G Fuel Air Separation System
If you drive a 1998.5-2004 Dodge Ram 2500 or 3500 with the 24-valve 5.9L Cummins and you are fighting hard starts, power that falls off on a grade, or a VP44 you do not want to replace again, the supply side is the first place to look. The AirDog II-5G DF-100-5G (part number A7SPBD253) is a frame-mounted lift pump with built-in air separation, a water separator and a 2-micron filter, sized at 100 gallons per hour for trucks running stock fuel. This version is for trucks that still have the factory engine-mounted lift pump, not an in-tank pump.
From the factory these trucks feed the injection pump with a small lift pump mounted on the engine and a block-side filter housing. The 1998.5-2002 trucks use the Bosch VP44 rotary pump, and the 2003-2004 trucks use the CP3 common rail pump. Both rely on diesel for cooling and lubrication, so weak supply pressure or air in the fuel is hard on them.
The AirDog mounts to the frame rail on a bracket and pulls fuel from the factory suction fitting at the tank module. Fuel passes through the water separator, then the gerotor pump, then the 2-micron filter before it goes forward. Entrained air and vapor are pulled out and sent back to the tank through a tee in the filler neck. The pressure side runs straight to the inlet of the injection pump, bypassing the factory filter housing and engine-mounted pump. A diaphragm regulator holds pressure, preset at 15-17 psi for this application, and recirculates unused fuel back through the separator.
Put a fuel pressure gauge at the injection pump inlet and watch it at idle, then under load on a road test. Pressure that drops toward zero when you lean on the truck points at the supply side, not the injection pump or the engine. If the engine pulls but the tach flares on a shift or under load, you have a transmission slip rather than a fuel issue; our guide to 48RE Cummins transmission problems walks through how to tell the two apart. Also check the tank pickup, the suction line and the filter, since a restriction ahead of any pump will starve it.
AirDog lists A7SPBD253 for the 1998.5, 1999, 2000, 2001, 2002, 2003 and 2004 Dodge/Ram 5.9L Cummins 24-valve. It covers both the VP44 trucks (1998.5-2002) and the early CP3 trucks (2003-2004); the manual gives a separate supply-line procedure for each. If your truck has had an in-tank pump installed, you need the version made for that setup instead: the AirDog II-5G DF-100-5G for trucks with an in-tank pump. If you run larger injectors or more fuel, step up to the 165 GPH version. Not sure which you have? Send us your year and VIN before ordering. You can see the rest of our diesel fuel parts in engine performance, and drivetrain parts for these trucks in our 47RE collection.
Plan filter service from day one: AirDog gives typical filter life as 15,000-20,000 miles, with the water separator replaced every other filter change. A spare AirDog II water separator filter is worth keeping on the shelf.
| Brand | AirDog |
| Part number | A7SPBD253 |
| Fits | PureFlow AirDog II-5G 98.5-04 Dodge 24V 5.9L Cummins (w/o Pump) DF-100-5G Fuel Air Separation System |
| Type | Fuel Air Separators |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Yes. A7SPBD253 is listed for 1998.5-2004 Ram 5.9L 24-valve trucks, which includes the 2003-2004 CP3 trucks. The manual has a separate supply-line section for them, and removing the factory filter housing on those years needs a filter bypass.
It means the truck does not have an in-tank fuel pump. This version is for trucks still using the factory engine-mounted lift pump. If your truck has an in-tank pump, order the version made for that setup.
It is preset from the factory at 15-17 psi for this application. The regulator is adjustable, but AirDog warns that running above 75 psi shortens pump life and more pressure does not mean more flow.
AirDog sizes the DF-100 for stock fuel trucks. If you have added injectors or heavy tuning, the 165 GPH version is the better fit.
AirDog lists typical fuel filter life at 15,000-20,000 miles depending on fuel quality, with the water separator replaced every other filter change. Drain the separator about every three months.
No. The harness relay plugs into the factory two-pin lift pump connector so the ECM still controls the pump, and the power leads go to the alternator or battery.
