If your fabric is not feeding correctly there are a couple things you can look for. First check to make sure you or someone hasn't lowered the feed dogs. If so, there should be a switch some where to release them from the locked position. Many types of machines will have some kind of icon somewhere by the knob showing you a darning feature.
Second, if the feed dogs appear to be up, remove the throatplate and clean the lint from around the feed dogs. I have seen so much lint in some machines that it looks like felt. Once removed, oil metal-to-metal parts with a good sewing machine oil.
You should see the feed dogs move and the teeth come up higher than the openings on the throatplate. If none of these things work I would oil all oiling points to make sure the metal parts haven't seized up. Otherwise you may need to have a tech check for slippage on the gears.
One last thing.. make sure your stitch length is set to 2.5 or 3 and has not been left at 0 or 1. And, if it was me I would check the presser foot pressure as well.
hth
Lori H.
July 2007