We just got back from a cross country trip (see separate email) and had to
run the fridge on DC while driving since it wouldn't stay lit on propane
while moving, even though it used to.  I had recently carried out some
fridge maintenance (air pump upgrade, clean combustion chamber, and install
bigger and quieter fan), and so I assumed I must have messed something up,
and would have to remove the fridge again to try some trial-and-error
troubleshooting.

But then, we ran out of propane, and when we went to fill up, the propane
attendant said it only took 1.1 gallons or so.  Our tank has a manual
fill+bleeder valve system.  I knew this was low but he said he was sure it
was full, so I drove off puzzled.  Then, I got concerned, as I started
getting the distinct whiff some propane while driving.  When I pulled over
to check it out, I found that the emergency vent on the propane shutoff
valve (not the regulator) was leaking in spurts, especially while driving.
It continued to do this for a while, but after while it quieted down and
seemed not to leak to much more.  Here is my wild theory about how all of
this fits together:

Obviously, the vent is bad.  I'm thinking that maybe it is defective in a
way that makes it unable to hold back liquid propane.  So, whenever the
propane guy had put in enough propane that liquid was at the level of the
shutoff valve, lots of stuff started coming out.  Maybe this happened around
1.1 gallons, and he mistook it for liquid coming out of the bleeder valve,
and decided the tank was full.

If this is the case, then the idea is that when driving around, the liquid
sloshes, and whenever it gets up against the vent, the vent opens for a
second and lots of propane escapes.  I'm thinking that maybe this venting
creates enough of a pressure drop that the fridge flame goes out.

So what do people think... sounds plausible?

In any case, I think the vent is bad, so I need to replace this shutoff
valve.  Anybody know where I can get one without buying a whole new tank?

Thanks very much!
Wes