I would think it would be the one on the left, typically your feed is the largest of the lines (usually 1/2 line)

 

Thanks for the response so I’m assuming that the return would be the next biggest?

 

Big line should be supply, Smaller one all the way to the right should be return. Air dog should have instructions.

 

Should I be able to follow the fuel line from the fuel control module all the way to the tank? And that should be the fuel feed?

 

Once you get your lift pump you'll see it's much easier to figure it all out with the instructions in your hand while you're laying under the truck on the drivers side. You'll never even see the part you have pictured unless you drop the entire tank, which you don't have to do to install the lift pump. The only thing you will need is the little plastic GM 1/2" fuel line disconnect tool, local auto parts stores have them in their tool section, it'll be a small package with a bunch of different sized different colored plastic pieces in the package, you just need the 1/2" one. All you'll be doing is removing 2 feet of flexible hose that has quick disconnects on both ends of it, air dog gives you new connectors that just plug right into the existing fuel line. One line (the "fuel in" side to your lift pump) is on top of the fuel tank, at the front, a couple inches in from the center of the truck, its the bigger of the two hoses you'll see. Put the tool around the hose then push it in towards the fitting till the hose comes off, if it seems hard you're doing something wrong. It looks impossible to get to at first, but it isn't, its just within reach. The other end of that 2 foot flexible fuel line you're removing is easier to get to, its directly in front of the fuel tank and above the fuel cooler (the thing that looks like a tiny radiator that most people mistake as being their transmission cooler). You might want to do that one first so you get a better idea of how the tool and the disconnects work before you try doing the blind one on the top of the tank.

AirDog gives you new connectors that just push in to where you just took that 2 foot section out. Leave the return line alone (it's the smaller line). The AirDog has it's own return line that's going to cut into the big hose coming off where you put the fuel in your truck at.

I added a 30PSI fuel pressure gauge to mine so I can see the lift pump working and know when the filter needs to be changed, they sell a dummy light add on that should have just been included with the AirDog system (as well as the cheap little plastic disconnect tool), I'd suggest the pressure gauge over the dummy light. I myself went with this particular one...

Black & Blue MaxTow 30 PSI Fuel Pressure Gauge

MaxTow’s Black & Blue Double Vision™ 30 PSI Fuel Pressure Gauge Reads Your Diesel Truck’s Lower Fuel Pressure From 0 to 30 PSI with Incredible Accuracy.

www.maxtow.com

I point this out before you install the lift pump because it will be much easier for you to install the sensor the gauge comes with on the lift pump before you put the lift pump on your truck. There's a 1/8" NPT threaded hole towards the front of the lift pump that has a plug in it, you unscrew the plug out and screw the sensor for the gauge into that hole. Much easier to do before you install the pump since the hole will end up being between your pump and the frame at the top. I suggest the 30PSI gauge because that will put you right in about the middle of the range of the lift pump, the 15 psi is too low and the 100 psi gauge is too high. You'll also find the gauge useful over the dummy light if you want to adjust your pressure regulator on the lift pump. They say they come factory preset at 8psi, mine came factory preset actually at 12.5psi (where I just left it set at).

I saved that little 2 foot section of flexible fuel line, washed it off with Dawn in the kitchen sink so it doesn't smell, put the little plastic tool around it and tossed it behind my seat. I figure if I ever have an emergency roadside or parking lot problem with my lift pump, electrical, mechanical or just a plugged filter, I can always use it to completely bypass the lift pump in under 2 minutes.

 

Yes, but I would follow it from the fuel filter head on the passenger side of the engine, It comes up on the drivers side then connects with a quick connect fitting to a steel line going to the fuel filter head, Larger line is the supply and the smaller one is the return.The air dog also has it's own return line from the pump itself that usually plumbs into the fuel tank filler neck. The instructions that came with my air dog were fairly simple.

 

Air dog must be getting cheap when I got my set up it replaced all the fuel line from the tank to the engine bay eliminating all the old fuel supply line and the problems associated with it.

 

They don’t do that now, on my crew cab I think I ended up with about 3’ at most of extra left over hose. I wouldn’t have wanted to replace all my steel rigid fuel line with rubber hose though.