Dell 1133 not printing middle of page

I have just changed the cartridge of my Dell 1133 and it is only printing and inch of the left side of the page and an inch and a half of the right.  It is a very clean empty patch down the centre, as though someone has photocopied something without realising the previous person had left a strip of paper in the photocopier. I have taken the cartridge out and tried to distribute the ink more evenly, but to no avail.  Any suggestions would be welcome.  Many thanks in advance.