shmelb

The pump on the shmelb is like a Tilley, so the whole pump unscrews to put fuel in it. I can take apprt the chech valve easily from the outside. the check valve rubber seems to be ok.

With a normal bucket, when you pump, the bucket pushes the air into the tank. When you pull the plunger out again, the bucket lets air past it because of it's shape, so you can pull it out without creating a vacuum, and the pum tube gets refilled with air.

However, an oring is thesame shape all around, so it pumps on the out stroke as well. But alot of stoves use orings, so what's wrong here?