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Hi Don,
Yes, it seems some plug(s) are fouled.......BUT, the lead does not melt
off, (but is vaporized IF CYL Temps are high enough)...I suspect the idle
mixture may be too rich, causing carboning of the plugs...and the switching of
the plugs may be misleading.
One way to check is to start the engine on the mag that runs
rough, and let it run for about 30 seconds. Shut off engine and check
the exhaust stacks to see which cyl is missing. The missing cyl exhaust stack
will be cold...
Change out this cyl spark plug. See if it is black with soot ( carbon),
etc.... Now replace with a "good" plug ( or change it to another cyl and check
again- to see if the plug itself is bad.)...
Make sure the idle mixture is not too rich...
Go flying and enjoy.
BTW, I ran auto gas for about 10+ years, until I had to let the coupe sit
un used for a period. Then refueled with a 5 gal can of foul smelling unleaded
auto gas. Apparently, there was insufficient separation between gasoline and jet
fuel in the pipe line. (All fuels are pumped thru the pipelines, and a slug of
fuel separating the different kinds is drawn off, and re-refined), and the gas
contained fuel oil or untreated jet fuel. Jet fuel is now treated with an
algaecide at the refinery...used to be the airport had to add algaecide at the
jet fuel stand.
After a few weeks, I found algae growing in my tanks..green goo drained out
the sumps. Recognizing this is prevented by adding an algaecide to jet fuel, I
obtained some PRIST algaecide, and stopped the problem. Still made a mess in the
tanks which was a pain to clean up. I now recognize that unleaded fuels do not
kill algae, as does lead..... and that the problem does not occur in autos
because the tanks are sealed against air, thus no water to support the growth of
algae.....
I have now been using 100 LL for about 5 years, with never having a leaded
plug problem... ( probably should never have said this :) )... I do run the
engine at 2400 - 2450 rpm in an attempt to keep internal cyls temperatures hot
enough to vaporize the lead, and get rid of it. Also try to keep idle
period to absolute minimum, as at idle the mixture is already rich, and can
cause plug fouling.....So far, so Good.
Hope these thoughts help.
Fly Safe - Have Fun
Harry Francis
Elliston, VA
N93530
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