On Sep 28, 2004, at 2:51 PM, Don Abbott wrote:
I have a gas leak from the bottom of my Stromberg carburetor.
Don Abbott
415-G N94411
Hi Don,
It's important to ascertain if you have a crack, etc. in the carburetor, or if the leak is merely OFF the bottom having originated somewhere inside up higher. A gas leak from the fuel pump or elsewhere that runs down the outside of the carb is a time bomb to be fixed before next flight.
A slow leak from inside is quite common problem, since paying someone to fix it doesn't assure you won't have the leak back after your check clears. For all practical purposes, if it's the needle and seat this tiny amount of fuel makes no difference when the engine is running. Just priming the engine releases raw fuel from the carb; so some learn to (safely) live with it.
Add to your "shutdown" checklist to shut the panel (or behind-panel) valve in the line from the fuselage tank to the carburetor before shutdown (run the fuel out to stop the engine). THEN shut off the Ignition Switch followed by the Master Switch. No fuel, no leak! (no leak, no vapors to form an explosive mixture awaiting a spark)
I'd also add to the "Startup" checklist to turn this valve back on, but you can't forget it. The engine won't start with no fuel in the carb; and the primer also gets its fuel AFTER this valve.
An additional advantage is elimination of the varnish buildup (ring around the carburetor) in the area of usual evaporation between flights. An unfortunate disadvantage is elimination of your "automatic" P-Lead check (observing engine quit when Ignition Switch turned off).
Regards,
William R. Bayne
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Copyright 2004
