I believe I need to bleed the propane line to my furnace. The propane tank ran empty and the furnace lit only briefly right after the tank was refilled. (It's possible that the propane tech and I were both mistaken and we just heard the fan and not the burner.)

But I can't find where to bleed the line. It's far more complicated than a water heater. I have the main valve in the 3/4" line into the unit. There is the on/off valve inside. And that's all I can find. There are a couple of places inside where it looks like I could open one of the copper lines, there are capped T-joints with removable caps, but they aren't at the top which is where I would expect to bleed from (since propane is heavier than air).

The restart instructions say to turn off the thermostat, the main power to the unit, the gas supply line and the on/off valve inside, wait 5 minutes, turn on the on/off valve, put the covers back on, turn on the gas supply and the power, then turn on the thermostat. I've been through that cycle about a dozen times. The fan comes on and I hear the clicking of the ignition spark, 3 or 4 times a second for about a minute. Then it all shuts off. Sometimes the fan and the spark start up again right away, still with no ignition, sometimes it sits and I can get it to start trying again by throwing the power off and on again.

I get a very faint hint of propane smell which I think is coming from the gas that is not being ignited by the spark. If I have gas and spark, I should get ignition, unless the gas has air in it and is not concentrated enough to light. Which is why, combined with the tank running empty, makes me think I need to bleed the line.

But so far my only method for bleeding is to get a little bit more out each time I go through the shut-down, wait, try-again cycle. There has to be a better way.

Any suggestions for how to find where to bleed the propane lines?