You have a wrong idea about the gas flow control. There are only 2
setting of gas flow. Pilot flow and full burner flow. Changing the
setting of knob C does NOT directly change how much gas is flowing. All
it can do is change how often the fridge switches between pilot flame
and full flame. There is NO gradual adjustment of flame size, only full
flame or pilot flame. The inside temperature of the fridge is maintained
within a set range by switching back and forth between pilot and full
flame as often and as long as is needed to match the setting of the C knob.

If anything I would consider that you have too much gas flow for the
available oxygen. There used to be a high altitude kit for the 182,
consisting of a burner jet with a smaller hole. This slightly reduced
the size of the burner flame to better match the flow of available fresh
air needed to sustain an even flame. Perhaps someone messed up your
existing burner jet, for example by poking something through the tiny
hole. The jet is made of soft metal and nothing hard should ever be used
to try to clear it.

I think the rumble is the flame struggling to sustain itself in a low
oxygen mixture. Either the air circulation is obstructed or too much gas
is available.

Perhaps you did the manometer measurement incorrectly? As one liquid
level goes up the other level goes down and you measure the difference
between the two active levels.

Mark

Leonard Sitongia wrote:
>  I tried playing with the level (C) to see if perhaps there is too much gas pressure, and it's preventing enough oxygen from getting in. I couldn't find a level that would keep it going in the normal flame appearance mode. It rumbles in the pipe as long as I keep pumping. When I stop pumping, it will rumble on for a minute or two, then there's a click and it goes off (or it goes off first... seems simultaneous).
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