Had my Barista (the espresso machine, not the guy who makes my coffee) upside down and dry for about 2 years and had a helluva time priming the pump. Had to hold the feeder tube high above the machine, constantly shooting water into it from a large syringe/baster while alternating between the steam pipe and the coffee pathway. Took a good 40 min and about 50 alternations (and lots of swearing) but finally got enough water into the pump to prime it and am now good to go. So, if the pump is vibrating and making sounds don't give up too soon on it!