The big problem with these is the NRV at the bottom of the pump tube. I finally found some ?Vitron? rubber that worked as a replacement for the pip. Both the blow torches and plumbers furnace pumps are notorious for leaking by. You can tell when pulling up the pump handle results in a hand soaked in CF. Consequently, when the Franks are burning I pull the pump handle up for the first pump VERY slowly.
I've had good luck finding automotive O rings the right size I could cut and make work... Cutting them straight is not always easy but o rings are cheap I like a positive shut off myself