I think the best thing to do when the valve is leaking, is to get a replacement valve. This fixed my problem. My pump leaked like this when I got it. The new valve fixed the leaking.
Sometimes in shipment something happens to the valve (not common but it happens). I remember I tried everything to get it to work. The only thing that fixed it, was to get a replacement valve.
Oh sorry! Okey I see. Maybe
@MrBig29 was using it incorrectly.
This was really misleading if he was indeed using it incorrectly: