I have just pulled the fridge yet again.

By removing the air tube, I conclude that most of the resistance in the pump
is the friction of the rubber against the walls of the piston, not the air
resistance.

I removed the pump again, cleaned it, and then replaced it using a light
machine oil this time.  Last time it was silicone spray.  It is slightly
improved now, but still sticky,  not nearly as easy to pump as the pumps on
the old Coleman white gas stoves, which are a very similar design.  It is,
as far as I know, the original pump.  The rubber diaphragm is not degraded
in any apparent way.  It's just very tight in the cylinder.  Any ideas on
how to loosen this up?

As for the possibility that the thermocouple is not in alignment with the
flame:  anyway to test that theory without opening the firebox?  I just
worked really hard earlier today to caulk that firebox tightly closed and
really hate to re-do that.

Thanks,

Paul