23rd May 2014, 12:43
That should go to the fuel petcock next to the fuel line; the XJ's use a vacuum operated fuel "pump" located inside of the petcock. When synchronizing the carbs, you use these same ports to tap into the individual carbs to set them all the same with a manometer (you can make one, YouTube has dozens of lessons on those).
26th Apr 2011, 18:05
That tube goes to the petcock.