Fuel Filler Neck Extension

[Jimmy]

I have a 2017 Jayco Seneca with two diesel tanks.  The fuel filler necks are short and they are located on the top edge of the fuel tank, not all the way on top.  Located this way I cannot completely fill the tanks as the filler neck is below the top of the tank.  Can anyone guide me to a vendor that sells extensions for diesel fuel tank filler neckss.  It is just a bad design on this motorhome, but I am losing about 5 gallons capacity in each tank.

The extensions would need to screw on to the filler neck, in place of the cap, then the cap would screw on to the top of the extension pipe.  Any help or guidance on this would be much appreciated, as this is frustrating.  The tanks should hold 74 gallons combined, but probably don't hold much over 60 gallons.  I have seen this problem asked on Jayco forums and other motorhome forums, but have not seen a positive response yet.  Neither Jayco nor Freightliner are of any help on this issue.

Thanks, Jimmy

[lenp]

I would think an air pocket in the top of the tank a good idea to allow for expansion.  My previous rig (2003 International Toter) had saddle tanks and the bottom of the fill hole was about two inches below the top of the tank - no way to "fill to the brim".  That air pocket was part of their design.

I would not want to completely fill a tank with fuel from an underground tank (maybe 50-60 degree fuel) on a 100 degree day and have the tank(s) start to expand when the fuel warmed up.

Lenp

[Jimmy]

Thanks for your reply Len.  I was traveling after I posted this and just failed to respond.  The air pocket is appropriate and good; they're just forcing more of a pocket than needed.  I guess that I am settled into accepting them as they are, as I haven't found a good solution.

Thanks, Jimmy