Premium Fuel Pump and complete filtration system

By Angela McCorison

Let’s talk about air bubbles. Normally bubbles are fun and kids love them, but the bubbles we’re referring to are more like enemy bubbles, the kryptonite to Superman effect. We are talking about bubbles, (air/vapor) in your fuel and considering most diesel engine failures originate in the fuel tank, this is a thing of importance. Water in your fuel is also important to get rid of as air often brings moisture, this happens more often than you’d think. Diesel fuel can contain two types of water, “water in solution” or “free water.” Water in solution is water that may be dissolved in the fuel because Diesel fuel can contain (very) low levels of water. Water which is not in the diesel fuel as a dissolved component is considered Free Water. Temperature fluctuations can cause droplets to condense on the inside walls of fuel tanks and accumulation of water over time. Water in suspension in burning fuel reduces the amount of energy available and will result in lower horsepower output. Water dissolved in the fuel, (Water in Solution) at low levels is not necessarily a problem. On the other hand, free water, in diesel fuel could result in excessive injector wear, filter plugging, power loss and corrosion of engine fuel system parts.

The AirDog Solution
Who doesn’t want clean fuel? Would you rather have a cookie straight from the jar or let someone sneeze on it first? Unless contamination is your thing, it’s a given right? The AirDog II Fuel Preporator is your new friend from fuel contamination of water and air. The AirDog system removes water, particulates and entrained air from the fuel. The entrained air separated from the fuel is returned to the tank through a small return line. The fuel is then delivered to the engine at the correct pressure flow to meet the demands of the engine under all operating conditions. This, in turn, leads to: Increased Fuel Economy, Increased Power Output, Increased Torque Output, Longer Injector Life, Improved Throttle Response, Reduced Exhaust Emissions and Optimized Engine Performance.

The kit that AirDog sent us is the AirDog II DF-165-4G Fuel/Air Separation System for DuraMax diesel engines. If you are interested but don’t have a DuraMax diesel engine, you’re in luck – AirDog offers a wide variety of systems for just about every diesel pickup truck on the market today. (AirDog:, 877-421-3187)

Tools Needed
7/16” Wrench
½” Wrench
9/16” Wrench
5/8” Wrench
¾” Wrench
10mm Wrench
3/16” Allen Wrench
½” Fuel line disconnect tool
Flat head screwdriver
Razor knife

The AirDog II Fuel Air Separation System featuring Demand Flow Technology
The AirDog II receives fuel under vacuum from the fuel tank containing entrained air/vapor, particulate contaminates and unknown quantities of water.
The fuel passes through the water separator which removes the large particulate contaminates that could damage or jam the gerotor fuel pump. The fuel, with only entrained air/vapor and tiny particulate contaminates remaining, then enters the fuel pump.
The fuel, now under positive pressure flow, enters the fuel filter. As the fuel passes through the filter media and the remaining particulate contaminants are caught and contained, the entrained air/vapor is also separated. Through the positive fuel air separation features of the patented AirDog II, the separated air/vapor is discharged from the filter and back to the fuel tank through the Primary Air/Vapor Discharge Port.
The fuel passing through the filter media is now free of contaminates and power robbing air/vapor. At pressures and flows able to meet the needs of the engine, it exits the fuel filter through two passageways. First, the fuel for the engine passes into the fuel pickup tube and on the engine. Then, the excess fuel not needed by the engine recycles internally through the pressure regulator back to the water separator. Check out the how it works video at:

The AirDog II DF-165-4G all-inclusive kit including; AirDog II Pump Assembly w/ water separator and 2 micron fuel filter, Relay control wiring harness, Fuel module upgrade, all fuel fittings required, mounting hardware, ½” fuel lines w/ OEM style quick connect fittings, AirDog II bracket & spacer, plastic ties, O-ring service kit and install manual.

Before starting, chock the vehicle’s tires to prevent rolling and use proper supports when working under your truck. Disconnect the battery cables to (both) batteries. Mount the AirDog II assembly to the metal mounting bracket using 4 of the 1 ¼” long x 20 cap screws with lock washers & nuts. To get better access to the nuts, unscrew and remove both filters. After the mounting bracket is all tightened down, grab the spacer and the frame plate (with more holes). Install the frame plate and spacer onto the back of the mounting bracket using 4 of the 3” long socket head cap screws with lock washers & nuts. Note: The AirDog II can be mounted on the inside or the outside of the frame, but preferred mounting is on the inside. We, however, mounted ours on the outside of the frame because of our addition of a Titan 62 gallon fuel tank. Keep in mind, when you mount the AirDog II to the outside, the suction and return lines will be opposite as they were intended. We, in turn, decided to flip the AirDog II assembly so that the hose fittings would face in the desired direction.

Now, grab one of the 1/2” male quick connect x 3/8” NPT fittings, lubricate the threads with anti-seize and install into the “Fuel In” port using a ¾” wrench. Grab the other 1/2” male quick connect x 3/8” NPT fitting and install into the “Engine” port using a ¾” wrench. Last grab the 3/8” male quick connect x 1/8” NPT fitting, lubricate the threads with anti-seize and install into the “Tank” port, (which is the smaller port next to the “Engine” port) using a 5/8” wrench.

Next up is mounting the assembly to the driver’s side of the frame. Grab the frame backing plate and clamp the frame between the AirDog II bracket assembly and the backing plate using 3, 3/8” x 4” bolts, lock washers & nuts. The bracket is adjustable so be sure to adjust the position of the AirDog II on the frame as necessary for clearance. Properly torque all fasteners.

We need to install the fuel supply line to the engine, but first, we need to remove the factory fuel supply line from the fuel tank suction tube. Place the ½” disconnect tool around the fuel line and press into the Quick Connect fitting to release the locks. Carefully pull the factory quick connect fitting and fuel line from the fuel tank suction fitting. (The disconnect tool(s) can be purchased from your local auto parts store.)

Disconnect the other end of the fuel supply line from the steel line. (The connection to the fuel line is located on the front of the fuel tank. It will be the larger of the two lines that are on the frame.) You can then remove the 18” factory flex line.

Attach the fuel line, by pushing, the female ½” quick connect the end of the “pressure hose assembly” onto the factory male quick connect that was disconnected. You will hear a “click” when properly connected.

(Any excess fuel hose can be addressed by routing the hose in a fashion to take up the extra length, or a section of the hose can be removed.) Push lock splices have been included if you choose to remove the excess hose. Note: Properly secure all fuel lines to prevent damage from heat and abrasion.

Fuel Suction Line. Insert the female quick connect end of the “Suction Hose Assembly” into the previously installed male fitting in the “Fuel In” port. A “click” will be heard when the fitting is properly connected. Next route the fuel line “Suction Hose Assembly” up along the frame back to the fuel tank making sure not to kink or route the hose in such a manner where it can be damaged. Use supplied tie straps to secure hoses safely.
Route and attach the female ½” of the “Suction Hose Assembly” to the male quick connect fitting. You will hear a “click” when properly connected.

Next is installing the “return to tank” assembly (shown here) into the filler tube. Note the arrows: Install the filler tube with arrows pointing toward the tank!

Cut filler tube as shown here, removing ½ inch. Loosen hose clamps on each end of filler tube.

Insert “return fuel filler tube” assembly in filler tube, as shown here. Properly tighten hose clamps.

Insert the female quick connect end of the “return hose assembly” into the previously installed male fitting for the tank port. The fitting will “click” when properly installed. Attach the other end of the “return hose assembly” onto the male end of the “return fuel filler tube”. A “click will be heard when the fitting is properly connected.

We had already put our filters back on the AirDog II assembly, but you can wait until now to thread them back on. Use oil to lubricate the filter seals. Pre-fill the Water Separator with diesel before install to help prime the pump.

Moving on to the wiring harness. Pop the hood and remove the plastic housing around the fuse box. Use a voltmeter to find a fuse terminal that is HOT only when the ignition is in the “on” position. Connect the “Red” Relay Trigger wire with the mini fuse tap to that terminal. Be sure to install the fuse that is removed back into the fuse tap we supply. Once installed into the fuse box the fuse tap should have both fuse spots filled. (TBC Batt, Ign 1 or 2, Acc and HVAC are commonly used to supply power.)

Route the red & black power supply leads to the alternator or the battery (shown here.) Connect the black lead to the chassis ground connection. Connect the red (Hot) lead to a positive junction box.

Route the wiring harness through the engine bay and along the driver’s side frame rail, to the AirDog II and connect the 2 pin Deutsch connector to the corresponding connector on the AirDog II. Secure the wiring harness to the truck with the supplied plastic ties. Note: There is an optional Indicator Light, which was not included in our kit, so we secured the pressure switch lead to the wiring harness with a plastic tie. We will also cover the pressure sensor lead to protect it for later use.

Next, follow AirDog’s “Initial Start Procedure.” See our startup on YouTube here: . We’re looking forward to the benefits of the AirDog II, now our engine will “receive air free fuel at the perfect pressure to deliver the power and the fuel efficiency that it was designed to create!”