It is the eve of our first camping trip in 15 years. I have a Westy interior
from a 1982 installed in my 1987 Syncro.
After cleaning the refrigerator combustion chamber and intake / exhaust
tubes of the fridge about a month ago, I was able to get the propane tank
serviced to full (it still had about a gallon in it from before), and
successfully got the fridge to light for the first time. I ran it for  about
two hours. It got nice and cold, no issues, and all was well.

I ran it again tonight. After two false starts, it finally lit. About two
minutes later, it started to make a soft single "fup" or "futt" noise (best
I can describe it); this occurs every 5 seconds or so, but not regularly,
sometimes it will go for a while, 20 seconds, without a noise. Looking at
the flame shows a little flash of yellow, but not always.

I let it run for an hour and a half, it still got cold, and remained lit
while I drove the van around the block.

I'm suspecting crummy propane. The only thing I didn't touch was the gas
jet. Modifying the position of the thermostat and gas valve doesn't seem to
make any difference. It had run very nicely before with no noise, so I'm not
suspecting the gas jet (yet).

Any ideas? The archives were mute on this particular subject (the noise, not
refrigerators).

Thanks,

Dave