Hi... i'm looking at this thread to resolve the head leak issue...
But, i also had jamming issues... I notice the jamming seemed to be more frequent when printing near the rear of the bed.. for me, it seemed to be more that the resistance from the spool and the tube.
I had bound the feed tube with the electrical cables going to the print head... when the print head moved to the rear of the bed it seemed the electricals were interfering with the 'natural' flex of the feed tube... I unbound them so the electrical cables dont interfere.
Conversely, when the print head is farthest away from the spool feed, the angle out of the feed mechanism it too great - i found if i tilt the feed mechanism (by lifting it up and out f the bottom 'hooks' it would feed better at long range. I was going to figure out some king of hinge for the feed mechanism to allow it to follow the pull of the tube somewhat... but in the meantime i tend to print nearer the centre.
Finally, I also noticed that the filament would tighten on the spool... when i make sure the filament is always loose on the spool (i always sit next to it while it's printing... rather it is next to my work station anyway).
I have seen some designs for better spool rigs.. the wooden ones seem to have too much resistance... perhaps some plastic sheet as bushing may free up the rotation...?
hope this may help some one... now back to pulling the head apart to fix the leaking..