Weed trimmer

Question

primer bulb does not pump full, and trimmer will run out of gas

I have a Mcculloch edge trimmer. I replaced the two fuel lines but the fuel Primer/Bulb does not fill. There seems to be be an air bubble that does not want to feed through. Where the fuel lines goes into the holes in the tank, does the intake and overflow fuel lines both be submerged under the fuel level, or is there a possibility that there are an air leak somewhere?