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Lynn.
Yes, I thought I had what I thought was a carb ice problems, and
enlarging the main jet seemed to make it noticeably better. This was
puzzling and didn't make much sense. After diverting cabin heat to the
front of the carb, enlarging the main jet and a few other things, all of
which seemed to make it better, it was still not right! I'll have to
admitt that I was quite wrong! It came to me as I lay in bed one night
thinking about the problem, as I had done a hundred times before. The
fuel line was heating up to the point that the fuel was boiling and
causing a vapor lock! The fuel line comes from the firewall, down over
the muffler to the gascolator on the lower firewall and then back up to
the carb. It MUST have no humps or high spots in the fuel line run,
rather it must run in a continuous slope down or up. Still the engine
only seemed to give trouble when backed off to about 2,200 RPM. This
again puzzled me until I realised what was causing the problem. At take
off and higher settings, the fuel ran through the line fast enough that
it didn't get a chance to heat up and vaporize. When backed off
somewhat, the carb bowl would fill, shutting off the needle valve, which
stops the fuel flow in the line. As the engine uses little fuel at low
settings, the gas would sit in the line long enough to heat up and
boil! Pulling the carb heat always restored power, but it was still
very disconserting. Carb heat enrichens the mix slightly giving the
needed fuel thirst to open the needle valve all the way and let the fuel
recharge the carb bowl, and off you go again. That's way running at
higher settings and/or enlarging the jet made it better, it kept more
fuel running through the line, thus not giving it time to boil. This is
the second Coupe I've had with this problem. I'd also be willing to bet
many coupes have this problem as well, as when I talked about this a
year or so ago, six or eight other Coupers said they had very similar
problems. This engine dying out stuff can put you right off flying, as
it almost did me! ......The solution......... As I am on the Canadian
Owner Maintenance program I can and have solved this problem once and
for all!! A trip to the local hardware store yielded a roll of 2"X1/8"
foam insulating tape with aluminium on oneside and sticky on the other.
I wrapped all the fuel hoses, overlapping as I went. When that was done
I folded heavy duty alum. foil over four times to make strips. I then
crinkled it up to give it more thickness and then wrapped it over the
foam insulation for added heat protection. Then I took fine lock wire
and double wrapped the foil to secure it in place. Done. The fuel line
now is about 1 1/2" in dia. and does look different, but IT DOES
WORK!!! I know some will throw their hands up in disgust but it
certainly has worked for me and my precious pink skin is more valuable
to me than all the rule books and manuals. There are quite often new
solutions to old problems if only we can keep our minds open to new
thought and careful experimentation. I cannot recommend that others do
what I have done as the big bad wolf (the FAA) my get you if you live
below the Canuck border. If you have a Coupe that sometimes dies out
for no reason, chances are vapor lock! I hope this may help of my
fellow Coupers.
..........................................Jon
Page.................................................
Flak Magnet 415-C
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