I don’t have JC turbines but I have engines that start with propane, it sounds like the chamber is not getting hot enough and the the startup sequence times out, if it’s not at the proper temperature the ECU won’t start the pump, on the second attempt it’s starts probably because the engine is hot already from the first attempt.
Adjusting the gas just a bit more at a time is the right way to go and what I would do, it has to get to the required temperature, all ECU brands have a fuel adjustment for this part of the startup sequence, I’ve done this adjustment to at least half of my engines because they were spitting flames on the startup part because the ECU was sending too much fuel.
Warm to hot days actually help the gas to flow easier than cold days, the gas tends to evaporate instead of staying in a liquid form like in cold days.
I suggest to concentrate on the gas part first before moving on to adjust the startup fuel, adjust the fuel once the engine begins to run on fuel if it is spitting flames or if it is taking too long to accelerate.
Add a few drops of 3 in 1 oil to the gas selenoid in the in side to lubricate it, then test it to get the oil in there, the propane is cold and in time it will get it dry and that can get them stuck close or opened, also confirm that the glow plug wire has been pulled out.
Auto pump mode is what you need for the startup fuel.
I hope this helps.
