manicmike

I would check the distance between the needle and hook, which should be as close as possible without them actually touching. Last one I saw which was skipping stitches had a large gap. It should be obvious how to check it and you can adjust the distance.

If that's not the problem then I'd check the hook timing. This is really easy, and well documented.

The Yahoo vintage singer files group has a copy of the adjuster's manual, which I'd highly recommend - lots of other info on the 319s.