Also check that you don't have a pinched fuel hose. Had this happen to me once: it acted like it was air-locking. I'd was going to pull the fuel line from my tank to check for blockages in the tank and I saw a stick jammed up against the fuel line. This was with my NX5510, and right near where a darn piece of brush popped the hydraulic return hose (from the hard line) on my B7800 (it bled to death right on the spot! had to tow it home; shortcomming of HSTs). Might also just look to loosen the fuel tank cap: you'll know right away if this is the culprit as there will be a vacuum and air will rush into the tank (assuming that your fuel system isn't pulling in air from somewhere else). Fuel cap isn't likely in this case, but it's something to keep in mind.