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Pureflow Airdog Fuel Filter - Filtering The Fuel

OC Diesel Shop Exposes The Flaws Of The Cummins Diesel And Offers A Remedy With The Pureflow Airdog II

Larry S. Saavedra
Jan 4, 2011
Photographers: Larry S. Saavedra
The 5.9L and 6.7L Dodge Cummins engine is a workhorse that embraces aftermarket high-performance products, which offer incredible boosts of horsepower and torque. The twist is that Cummins has a history of problems associated with its fuel delivery system.
Photo 2/11   |   pureflow Airdog Fuel Filter oc Diesel
Early-model Cummins mills with the engine-mounted fuel pump were so problematic-like quarter-tank fuel starvation, for instance-that Dodge issued a TSB (technical service bulletin) regarding fuel delivery issues. Many of these trucks were then retrofitted with newer in-tank lift pumps but never officially recalled.
Generally, a late-model stock Cummins will run fine with the factory in-tank sending module. However, it can't keep up with the demands of a highly tuned engine, and it can struggle with filter injector-killing air bubbles, water particulates, and fuel vapor, which dramatically reduce any performance gains.
To combat this, the newly improved CARB-certified, adjustable PureFlow AirDog II air/fuel separator and filtration system was developed to work with an in-tank fuel sending module, which allows for much higher volumes of cleaner diesel to be drawn from the tank without resorting to an external draw-straw.
Essentially, the complete PureFlow AirDog II kit feeds a constant supply of clean fuel to the injectors, and whatever is not used by each injector is trickled back to the tank, so there's never a shortage of fuel in the injector rail. Kits are also available for Ford and Chevy trucks.
As we mentioned, the factory Dodge fuel system is fine for stock vehicles, but once the horsepower and torque is increased through the use of aftermarket products, it can't adequately handle the fuel that high-performance engines require, leaving the door open to impurities, excess foaming, and other power-killing gremlins. While there are similar systems on the market, the PureFlow AirDog II kit is expertly crafted to fit like OEM, and it's easy to install thanks to new quick-connect lines that give it a professional, almost-factory appearance.
You don't have to have a highly modified vehicle to justify the kit upgrade, either. In fact, the late-model Dodge shown here was a stock daily driver that was driven frequently to Mexico's surfing spots along the coast, and it was never used for high performance. The owner complained to OC Diesel Shop about bad gas, which was slowly pitting his injectors and making his trips unreliable. He needed to filter out any chance of water getting to the engine on his next fill-up in Mexico. Installing a system like the AirDog II sets end users up for future engine upgrades, so they'll never have to deal with the limitations of the stock fuel system again. Thanks to the folks at OC Diesel Shop, we followed along as technician Greg Nelson took us through the process step by step.
The Overview
One of the most time-consuming aspects of the upgrade was removing the factory fuel tank. You don't have to drop the tank if you are able to lift the truck bed instead. But in our case, Greg had to drop the stock tank in order to access the stock fuel-sending module because the truck had a large camper. Once he removed it, he replaced the sending unit with a newly revamped unit from PureFlow that has larger fuel lines (1/2-inch) and better capacity.
"The entire installation was hassle-free, and I really liked the fact that the new PureFlow AirDog II kit is plug-and-play. Everything was included," Greg said. "The PureFlow AirDog II kit gives the end user the ability to push more power through a larger-diameter hose for better fuel flow, and it's adjustable."
Here's a few things you should know about the product before you get started: The filtering/pump system is a patented product with a California Air Resources Board E.O. number for diesel trucks, which is a big plus, because that means it will have no negative effect on your vehicle's warranty-as long as it is installed properly. When running, the PureFlow AirDog II kit was whisper quiet, and the fuel/air separation and filtration system mounted directly to the Dodge frame using factory locations. The fuel/air separation aspect of the kit claimed to filter up to 2 microns, and because of its pure delivery of diesel, better fuel economy and throttle response are almost a given.
The Wiring
The wiring harness features water-resistant Deutsch connectors, a relay, and fuse holder. Once the wiring is properly installed, the AirDog II is controlled by the engine's ECM. The wiring is very intuitive if all the steps are followed according to the instructions.
Filter Servicing
One sign that the water separator needs servicing is when you notice low fuel pressure to the engine. The AirDog II's water separator elements should be replaced at every 2-micron-fuel-filter change or if it becomes damaged or plugged. The system's gerotor assembly might also need occasional maintenance, which is very simple using only handtools.
The Results
What we saw was a very straightforward method of reducing the risk of a fouled engine due to water, air bubbles, or fuel vapors reaching the injectors. While the installation might require the help of a friend, the directions were very simple thanks to the illustrated diagrams that highlighted each step. The PureFlow AirDog II kit is a true factory replacement system.
Once the old in-tank fuel-sending module was removed, we got a good look at all the dirt and impurities that came out of the tank. It was significant, but expected.
Overall, we liked what we saw in terms of efficiency, and never again will this truck owner have to worry about bad gas-unless he orders the chili burrito at his favorite Mexican cantina.
What You Get
Pure diesel delivery to injectors
Improved fuel economy
Quick-connect installation
CARB-certified with lifetime warranty
Factory-style fitment


OC Diesel Shop
Mission Viejo, CA 92691
PureFlow Technologies
Shelbyville, IN 46176-9720



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