Does the FX run OK with the bubbles? I assume not. I had a similar problem with a tank on one of my planes. I had some debris in the pressure line which was blocking the pressure and when the engine was runnning, the vacuum in the supply line was cavitating the fuel and drawing bubbles. Check the lines by pulling off the supply and pressure lines and blowing into the pressure side to see if there is any blockage.
Good Luck,
Curtis