I had the above engine worked on. The VRO pump was bad, so they took it off and I mix the gas now. The engine was worked on last winter. I fired it up after a little tuning this spring. It ran great, no issues EXCEPT - once the motor is off for a day or so, I can not get the plunger to prime the gas lines. The plunger is new, so that can't be it. The mechanic put a small metal box that connects the gas lines and I take what used to be the original CRO oil line. If I remove that box and press the plunger, I get gas in the lines easily. I then placed the box back in line and press the plunger again - engine fires right up. If it sits though, I can't get the gas back in the lines until I repeat the above steps. Any idea as to what would cause this?