I began fettling this stove recently and have had a few issues. The pump cup leather was shot so I replaced it. The I noticed that it wasn't holding pressure and kicking kerosene back out of the NRV so I promptly replaced it. If you have read my earlier post you know that I only get about four pumps before the filler cap seal leaks also (gotta order parts). What is odd is that once I changed the NRV it now makes an unusual noise when pumped. It does pump and no kero seeps out. I have changed the NRV again to see if it was a faulty one from the manufacturer and no luck. Mine have the lead washer btw. I even tried adding some copper anti-seize compound to the NRV threads and that made the sound go away for about ten pumps but it came back. I do not know if the stove made this sound before as it would not build pressure when originally tested. Btw, the NRV is"two fingers tight" on the wrench because I did not want to strip the threads with the anti-seize compund added (over torque it). For clarification the sound is like air bubbling inside a pressure container. An echoing type of hollow sound. It may be due to my leaking filler cap seal but I am unsure. Has anyone else experienced something like this ? The dunk test shows no leaks coming from the NRV or pump area just the filler cap seal.