Pick up tube
It appears that you have been short changed. The pick-up tube should not go all the way to the bottom, (leave room for a little water or debris) but 6 inches is a little much.You may be able to add a section of plastic tubing to the end of your existing tube, but make sure the material is not affected by diesel fuel or any additives that you may use. The short tube could be the source of the air incursion if your fuel gets low or you are in heavy seas. If you have been searching for an elusive air leak, be sure to check the joint where the pick-up tube joins the fitting at the top of the tank. This is rare but should be checked, especially if you have the assembly in your hands. We quite often use a vacuum gauge to confirm that a system is air tight. An easy way to isolate an air leak is by inserting a section of clear hose in the line. This can be moved along the line, ruling out various components. ie: if air accumulates in the tube at a filter outlet and not at the inlet, you know what to fix.
