With the regulated return installed, we can look at actually removing the air from the system. Pure Flow Technologies of Jefferson City, MO, has been in the diesel fuel system market for years. Their AirDog Fuel Preporator units have been used in our light-duty diesel market for sometime and have become the leader in air removal systems. The AirDog FP-100 we installed on our project truck is a well thought out unit that is compact, quiet and mounts right inside the frame rail in front of the fuel tank.
The AirDog works by pulling fuel directly from your fuel tank at a constant rate and running it through a water separator where the filtering process begins. Once the fuel has run through the water separator it travels through the AirDog unit to the 2-micron fuel filter. Inside the filter the air is separated out of the fuel and forced through a small air bleed orifice and where it will then return to the fuel tank. The now air free fuel residing in the filter is picked up through a draw tube and sent out of the AirDog to your factory (or high flow replacement fuel) pump where it will then be sent to the factory fuel bowl to be filtered one more time before entering the heads and injectors. Diesel fuel that is free of air, water and vapor makes for quieter and a more efficient fuel burn (the reason behind these modifications).
Again, the AirDog comes with a complete set of instructions that walk you through the install step by step. They supply you with all the fittings, push-lock hose and a fully assembled wiring harness to make installation a snap. We had our system completely installed and the truck up and running in around three hours.
The new Regulated Return and AirDog helped out our fuel pressure issues significantly. Fuel pressure no longer fluctuates under normal driving conditions, however, it will still drop some at wide-open throttle. That drop under hard acceleration tells us our factory high-pressure fuel pump is either worn out, or just flat can't keep up with the demand (most likely the latter). We will address that problem later on in the build by replacing the factory pump with a larger fuel pump from FueLab. For now, our goal was to remove air from the system and improve our flow some, both of which we accomplished with the installation of the ITP Regulated Return and AirDog.
Next on the list of modifications to this little project truck will be changes to the factory transmission, installing some new ARP head studs and looking at rear end traction upgrades, with the installation of an Eaton True-Trac differential. It's hard to believe that just a year ago this $3500 truck was hauling tires around town. Amazing how far a little elbow grease and some new parts will get you.