Hopefully this pic comes out. The primer is actually a purge bulb which pulls fresh fuel through the carb, purging the air out of it, and returns the excess
to the tank. They used to just let it dribble out on the ground, but the EPA stopped that.
So you need to find the direction that your primer flows, the in and out nipple, by just pressing the bulb and see which side has suction, etc..
Now the out nipple connects to a piece of fuel line that just returns to the tank. The other nipple goes from the purge bulb and connects to the nipple on the bottom of the carb in the pic I put up.
The other nipple has the long fuel line that goes to the filter that dangles close to the bottom of the tank.