I have an OLD TCM FG25. That decided to not start in the middle of loading a container. Checked all the usual things, it has good spark, Full propane tank no broken lines that I can find. The Impco Valve appears to freeze up checked water level in radiator. After trying numerous things to get it started. I removed the Propane line to the top of the lock out and turned off the cylinder and purged the valve and tried to start with no propane connected and it does start and run for 10 seconds then stopes. I can repeat this by reconnecting the line turn on propane then disconnect and start again. Thinking it is the lockout valve that is allowing the system to be over pressurized I replaced it. Same problem. And it acts like and does appear to be frozen blocking the coolant flow. But prior to last Tuesday this life started and ran fine no overheat.

So I am thinking maybe a Bad J Valve or water pump not getting circulation to the J valve. Not having much luck finding info on a water pump Would appreciate any suggestions on what to try next. New J Valve? Water pump id i can find one. It does appear to be a Over pressure problem either from freezing or bad valve. Vacuum lines appear to be ok, and it will start and run with pressure is relieved by disconnecting the propane feen line to the lock out valve