I have been given a Datsun forklift from the early 80s that is propane powered. It won't start. If I spray ether in the mixer, it will run so it's not an ignition problem. Here is the layout: full propane tank with new lines and filter leading into the vaporizer. The vaporizer was a model j but thinking that was my problem, I replaced it with a new cobra vaporizer. That didn't solve my problem. On either vaporizer, I could push the primer button and get fuel into the mixer. There is no lock off valve on this machine. I don't know if that is normal or not. It seems like the fuel would all leak out if there wasn't one but it doesn't. I tried pulling the outlet hose from the vaporizer to the mixer off and checking for fuel flow. It flows if I push the primer but it doesn't appear to flow without doing that. I put the end of the hose in water to see if I could see bubbles. No bubbles. If I connect the hose back to the mixer and push the primer button for a second or two, it will eventually start to fire but quickly die as it runs out of fuel. So I need to replace the mixer? Shouldn't I have fuel flow out of the vapor hose? Do I need the lock off valve to control the flow of fuel? Why doesn't the fuel leak out with no lock off? Does the mixer somehow pull fuel vapor in through the vapor hose while the engine is turning over and that is why I couldn't see bubbles when I submerged it? I'm at a loss of ideas trying to figure out what to do next without just blindly throwing money at it.