Originally Posted by
prathmann
Sometimes the only problem is that the seal on the plunger has dried out. Unscrew the piece around the shaft and either squirt in a bit of oil or remove the shaft and apply a little grease around the seal.
Or the presta/schrader adapter is reversed. I use my zefal for both types and left the adapter in the schrader position. Leaked like crazy while trying to air up a presta.