If its the hinge that is definitely causing the problem - causing the cupboard door to spring open, then its binding. Unscrew one leaf of the hinge and pack it out using some strips of cardboard, screw it back on and try again. If the door is too big however, it will need to be removed and any proud edges planed off. Finally, it could just be the catch that needs to be adjusted to pull the door shut.
John, December 2007
