You gotta make sure you get the intake line completely full. That's one thing I do not like about the XP series is that priming thing they put on top of the intake. You have to close the valve on the bottom, unscrew the lid, and pour water until it is at the very top, then put the lid back on, open the valve, let it fill the canister, then do it again... otherwise it'll have air in the line and keep doing that.
"What, exactly, is the internet? Basically it is a global network exchanging digitized data in such a way that any computer, anywhere, that is equipped with a device called a 'modem', can make a noise like a duck choking on a kazoo." - Dave Barry