What's Going on Here?

[Jay Honeck]

In 2004 we experienced our #2 cylinder dropping off-line on take-off
from Titusville, FL, resulting in a quick return for landing. No
amount of high RPM leaning would clear it, so we de-cowled the engine,
took all 12 spark plugs out, cleaned them, put them back in, and all
was well.

Conditions leading up to this problem were unusual. It had rained for
several days, hard, and Atlas was parked outside. Since we didn't
really find any spark plug fouling that looked bad enough to cause
this problem -- yet it went away after cleaning the plugs -- I've
often wondered if it didn't have something to do with all that unusual
moisture in the air. In the end, we blamed it on running high-lead
avgas, and the long taxi due to a presidential TFR.

Fast forward three years. Today we were going to zip down to nearby
Muscatine for an after-work dinner flight. It has rained here for
several days in a row, hard. The plane was actually wet, inside the
hangar, mostly from water that had condensed on the cold metal
ceiling, and then fell on the plane.

Mary started the plane, and I could immediately tell that it was
running a bit rougher than usual. I couldn't put my finger on it, and
Mary didn't notice it after we started taxiing, but I knew it was
there.

When she got to the hold short line, it failed the run-up. The right
mag showed a drop of 200 RPM, and (according to the JPI engine
analyzer) the #2 cylinder was dropping off-line on the right mag. The
left mag was normal.

No amount of high RPM leaning would clear it, so back to the hangar we
went. Pulled the cowling, and the #2 cylinder spark plugs. No
fouling was noted, but I cleaned the plugs anyway, and reinstalled
them. I also probed the wiring, wiggling and checking for loose
connections. None were noted.

After reassembly, everything ran normally, and passed the mag checks.
I took Atlas around the patch, and all was well. WTF?

Some thoughts:

1. Since 2004 we have switched to the high-dollar Iridium plugs. As
stated, no fouling was noted, so I don't think the plugs are to blame.

2. Is it possible that the #2 cylinder spark plug wires are shorting
internally due to all the moisture in the air? Has anyone ever heard
of this happening?

3. Is it more likely that the mag itself would be affected by the
moisture? Has anyone ever heard of this?

The fact that this happened three years apart, in very similar weather
conditions, on the same cylinder, has me deeply suspicious. I'm
thinking that maybe de-cowling the plane and letting it sit in the
breeze (thereby drying out whatever moisture may be shorting the #2
cylinder's right-mag plug) actually helped to solve the problem more
than anything I actively accomplished by pulling the plugs.

Any ideas here, folks? What could cause this, and what's the fix?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[BT]

I'm just guessing here... but I would look at and replace the spark plug
wire.. moisture could be getting in somewhere and condensing.. causing it to
short out and not fire the spark..

I once had an old 74 AMC Matador Coupe.. I always kept a new distributor cap
in the car, on wet new England days.. it would short out.. and when I looked
inside there would be a carbon trace between two posts.. it would crack from
the moisture... no power.. if it would run at all... put on the new
distributor cap and be on my way.. picked up another new on at the NAPA
store the next day

BT

"Jay Honeck" > wrote in message
oups.com...
> In 2004 we experienced our #2 cylinder dropping off-line on take-off
> from Titusville, FL, resulting in a quick return for landing. No
> amount of high RPM leaning would clear it, so we de-cowled the engine,
> took all 12 spark plugs out, cleaned them, put them back in, and all
> was well.
>
> Conditions leading up to this problem were unusual. It had rained for
> several days, hard, and Atlas was parked outside. Since we didn't
> really find any spark plug fouling that looked bad enough to cause
> this problem -- yet it went away after cleaning the plugs -- I've
> often wondered if it didn't have something to do with all that unusual
> moisture in the air. In the end, we blamed it on running high-lead
> avgas, and the long taxi due to a presidential TFR.
>
> Fast forward three years. Today we were going to zip down to nearby
> Muscatine for an after-work dinner flight. It has rained here for
> several days in a row, hard. The plane was actually wet, inside the
> hangar, mostly from water that had condensed on the cold metal
> ceiling, and then fell on the plane.
>
> Mary started the plane, and I could immediately tell that it was
> running a bit rougher than usual. I couldn't put my finger on it, and
> Mary didn't notice it after we started taxiing, but I knew it was
> there.
>
> When she got to the hold short line, it failed the run-up. The right
> mag showed a drop of 200 RPM, and (according to the JPI engine
> analyzer) the #2 cylinder was dropping off-line on the right mag. The
> left mag was normal.
>
> No amount of high RPM leaning would clear it, so back to the hangar we
> went. Pulled the cowling, and the #2 cylinder spark plugs. No
> fouling was noted, but I cleaned the plugs anyway, and reinstalled
> them. I also probed the wiring, wiggling and checking for loose
> connections. None were noted.
>
> After reassembly, everything ran normally, and passed the mag checks.
> I took Atlas around the patch, and all was well. WTF?
>
> Some thoughts:
>
> 1. Since 2004 we have switched to the high-dollar Iridium plugs. As
> stated, no fouling was noted, so I don't think the plugs are to blame.
>
> 2. Is it possible that the #2 cylinder spark plug wires are shorting
> internally due to all the moisture in the air? Has anyone ever heard
> of this happening?
>
> 3. Is it more likely that the mag itself would be affected by the
> moisture? Has anyone ever heard of this?
>
> The fact that this happened three years apart, in very similar weather
> conditions, on the same cylinder, has me deeply suspicious. I'm
> thinking that maybe de-cowling the plane and letting it sit in the
> breeze (thereby drying out whatever moisture may be shorting the #2
> cylinder's right-mag plug) actually helped to solve the problem more
> than anything I actively accomplished by pulling the plugs.
>
> Any ideas here, folks? What could cause this, and what's the fix?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>

[[email protected]]

Jay Honeck > wrote:
> In 2004 we experienced our #2 cylinder dropping off-line on take-off
> from Titusville, FL, resulting in a quick return for landing. No
> amount of high RPM leaning would clear it, so we de-cowled the engine,
> took all 12 spark plugs out, cleaned them, put them back in, and all
> was well.

> Conditions leading up to this problem were unusual. It had rained for
> several days, hard, and Atlas was parked outside. Since we didn't
> really find any spark plug fouling that looked bad enough to cause
> this problem -- yet it went away after cleaning the plugs -- I've
> often wondered if it didn't have something to do with all that unusual
> moisture in the air. In the end, we blamed it on running high-lead
> avgas, and the long taxi due to a presidential TFR.

> Fast forward three years. Today we were going to zip down to nearby
> Muscatine for an after-work dinner flight. It has rained here for
> several days in a row, hard. The plane was actually wet, inside the
> hangar, mostly from water that had condensed on the cold metal
> ceiling, and then fell on the plane.

> Mary started the plane, and I could immediately tell that it was
> running a bit rougher than usual. I couldn't put my finger on it, and
> Mary didn't notice it after we started taxiing, but I knew it was
> there.

> When she got to the hold short line, it failed the run-up. The right
> mag showed a drop of 200 RPM, and (according to the JPI engine
> analyzer) the #2 cylinder was dropping off-line on the right mag. The
> left mag was normal.

> No amount of high RPM leaning would clear it, so back to the hangar we
> went. Pulled the cowling, and the #2 cylinder spark plugs. No
> fouling was noted, but I cleaned the plugs anyway, and reinstalled
> them. I also probed the wiring, wiggling and checking for loose
> connections. None were noted.

> After reassembly, everything ran normally, and passed the mag checks.
> I took Atlas around the patch, and all was well. WTF?

> Some thoughts:

> 1. Since 2004 we have switched to the high-dollar Iridium plugs. As
> stated, no fouling was noted, so I don't think the plugs are to blame.

> 2. Is it possible that the #2 cylinder spark plug wires are shorting
> internally due to all the moisture in the air? Has anyone ever heard
> of this happening?

> 3. Is it more likely that the mag itself would be affected by the
> moisture? Has anyone ever heard of this?

> The fact that this happened three years apart, in very similar weather
> conditions, on the same cylinder, has me deeply suspicious. I'm
> thinking that maybe de-cowling the plane and letting it sit in the
> breeze (thereby drying out whatever moisture may be shorting the #2
> cylinder's right-mag plug) actually helped to solve the problem more
> than anything I actively accomplished by pulling the plugs.

> Any ideas here, folks? What could cause this, and what's the fix?

Back when I was in high school, I had an old Ford and worked at the
drive-in theater.

I carried a box of flares in the trunk to dry out the ignition system
on late, foggy nights so I could get home.

I would suspect minute cracks in the harness and condensation shorting
things out before the mags which are sealed a lot better than old
Ford distributor caps (which I also had to dry out).

I think I would get a spray bottle of water and on a dry day, spritze
the harness and see if it causes a problem.

If it does, replace the harness.

If it doesn't, spritze the mag and take appropriate action, but I would
bet on the harness having cracks somewhere near where it passes by the
airframe ground.


--
Jim Pennino

Remove .spam.sux to reply.

[Don Tuite]

The "WD" in "WD040" stands for "water displacement."

You're probably carrying around a can anyway. Next time, spray it on
the harness.

Don

[Orval Fairbairn]

In article . com>,
"Jay Honeck" > wrote:

> In 2004 we experienced our #2 cylinder dropping off-line on take-off
> from Titusville, FL, resulting in a quick return for landing. No
> amount of high RPM leaning would clear it, so we de-cowled the engine,
> took all 12 spark plugs out, cleaned them, put them back in, and all
> was well.
>
> Conditions leading up to this problem were unusual. It had rained for
> several days, hard, and Atlas was parked outside. Since we didn't
> really find any spark plug fouling that looked bad enough to cause
> this problem -- yet it went away after cleaning the plugs -- I've
> often wondered if it didn't have something to do with all that unusual
> moisture in the air. In the end, we blamed it on running high-lead
> avgas, and the long taxi due to a presidential TFR.
>
> Fast forward three years. Today we were going to zip down to nearby
> Muscatine for an after-work dinner flight. It has rained here for
> several days in a row, hard. The plane was actually wet, inside the
> hangar, mostly from water that had condensed on the cold metal
> ceiling, and then fell on the plane.
>
> Mary started the plane, and I could immediately tell that it was
> running a bit rougher than usual. I couldn't put my finger on it, and
> Mary didn't notice it after we started taxiing, but I knew it was
> there.
>
> When she got to the hold short line, it failed the run-up. The right
> mag showed a drop of 200 RPM, and (according to the JPI engine
> analyzer) the #2 cylinder was dropping off-line on the right mag. The
> left mag was normal.
>
> No amount of high RPM leaning would clear it, so back to the hangar we
> went. Pulled the cowling, and the #2 cylinder spark plugs. No
> fouling was noted, but I cleaned the plugs anyway, and reinstalled
> them. I also probed the wiring, wiggling and checking for loose
> connections. None were noted.
>
> After reassembly, everything ran normally, and passed the mag checks.
> I took Atlas around the patch, and all was well. WTF?
>
> Some thoughts:
>
> 1. Since 2004 we have switched to the high-dollar Iridium plugs. As
> stated, no fouling was noted, so I don't think the plugs are to blame.
>
> 2. Is it possible that the #2 cylinder spark plug wires are shorting
> internally due to all the moisture in the air? Has anyone ever heard
> of this happening?
>
> 3. Is it more likely that the mag itself would be affected by the
> moisture? Has anyone ever heard of this?
>
> The fact that this happened three years apart, in very similar weather
> conditions, on the same cylinder, has me deeply suspicious. I'm
> thinking that maybe de-cowling the plane and letting it sit in the
> breeze (thereby drying out whatever moisture may be shorting the #2
> cylinder's right-mag plug) actually helped to solve the problem more
> than anything I actively accomplished by pulling the plugs.
>
> Any ideas here, folks? What could cause this, and what's the fix?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"

I take a look at the inside of the "cigarettes" that go into the plugs.
They have a tendency to accumulate carbon and oil and then short out.

A Q-tip and lacquer thinner will clean them up nicely.

[[email protected]]

Jay Honeck > wrote:
> 2. Is it possible that the #2 cylinder spark plug wires are shorting
> internally due to all the moisture in the air? Has anyone ever heard
> of this happening?

I don't know about shorting internally, but shorting to ground is
possible. I'll add my vote to the list of votes for a bad spark plug
wire.

In a car, if a bad plug wire is bad enough, sometimes you can _see_ it
if you run the engine in the dark. You can see the sparks jumping from
the plug wire to ground. Doing this on an airplane - with a prop
whirring two feet away - might be interesting, though.

I was once able to manually detect a bad plug wire. A guy had an old
Ford Mustang and he thought it wasn't making full power. I started to
do a cylinder balance test on it - pull one spark plug wire at a time
and see how much the RPM drops, like a mag check but one cylinder at a
time. The first few wires produced a good drop, but I didn't complete
the check... the third or fourth one I tried zapped me as soon as I
grabbed the boot to pull it off of the plug. I discontinued testing
and advised him to get new plug wires. The moral is that if you feel
the need to diddle the plug wires with the engine running, get a good
insulated poking stick and maybe wear rubber gloves.

Look closely at the plug wire, especially where it goes under a clamp
or zip-tie or through a panel. If you can, loosen up the clamp or
zip-tie and pull the wire back a bit so you can see the part that was
under the clamp. Look for carbon marks on the wire or on any nearby
metal. Try bending the wire (not too sharply) at any suspect places
to check for cracks in the insulation.

Matt Roberds

Disclaimer: This is based on experience with ground vehicles. I don't
have an A&P; I don't even have a TG&Y. Some of this may not be
allowable owner maintenance. Your mileage may vary.

[Jim Burns[_2_]]

Left mag was normal would lead me to believe that your P lead is probably
ok.

Sure sounds like a moisture problem to me.

Right mag should fire the lower plug on the #2 cylinder. This would be one
of the longest plug wires, trace the harness back to the mag, check that the
harness standoff/adel clamps haven't vibrated through the insulation of the
wire to a point where a drop of moisture could ground the wire through the
clamp. Check any places where the harness may rub against baffles, cylinder
fins, ect. Check the wire where it enters the plug terminal. It may be
chaffed if the wire was tensioned against the terminal "nut". Use 2
wrenches when tightening the plug terminals, one to hold the terminal in a
position where no tension is placed on the wire, the second to tighten the
hold down nut.

As others have said, check the cigarettes for cracks, excess carbon, clean
them with MEK. Check the contact terminal "spring" to make sure it's
attached well and is long enough to insure proper contact with the plug.

Additional info from Sac Sky Ranch: http://www.sacskyranch.com/eng37.htm

Jim

[Jay Honeck]

> I take a look at the inside of the "cigarettes" that go into the plugs.
> They have a tendency to accumulate carbon and oil and then short out.
>
> A Q-tip and lacquer thinner will clean them up nicely.- Hide quoted text -

Thanks, Orval. I checked them, and they looked fine to me when I
pulled the plugs.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[nrp]

I agree it is probably a lead, but also as a temporary "fix" make sure
the plug gap on that cylinder (or all cylinders for that matter) is
near the recommended minimum to reduce the electrical stress on the
lead's insulation system.

[John_F]

When the engine warms up and sits during plug cleaning the engine heat
drys out the water in the magneto and/or the plug wire. Result is the
problem is gone. I would test the spark plug with a pressure test to
make sure it is not internally cracked and will fire under pressure
and I would also high voltage test the plug wire or just replace that
wire. Also inspect the distrubitor in the mag for carbon tracks.


On 2 Apr 2007 20:36:17 -0700, "Jay Honeck" > wrote:

>In 2004 we experienced our #2 cylinder dropping off-line on take-off
>from Titusville, FL, resulting in a quick return for landing. No
>amount of high RPM leaning would clear it, so we de-cowled the engine,
>took all 12 spark plugs out, cleaned them, put them back in, and all
>was well.
>
>Conditions leading up to this problem were unusual. It had rained for
>several days, hard, and Atlas was parked outside. Since we didn't
>really find any spark plug fouling that looked bad enough to cause
>this problem -- yet it went away after cleaning the plugs -- I've
>often wondered if it didn't have something to do with all that unusual
>moisture in the air. In the end, we blamed it on running high-lead
>avgas, and the long taxi due to a presidential TFR.
>
>Fast forward three years. Today we were going to zip down to nearby
>Muscatine for an after-work dinner flight. It has rained here for
>several days in a row, hard. The plane was actually wet, inside the
>hangar, mostly from water that had condensed on the cold metal
>ceiling, and then fell on the plane.
>
>Mary started the plane, and I could immediately tell that it was
>running a bit rougher than usual. I couldn't put my finger on it, and
>Mary didn't notice it after we started taxiing, but I knew it was
>there.
>
>When she got to the hold short line, it failed the run-up. The right
>mag showed a drop of 200 RPM, and (according to the JPI engine
>analyzer) the #2 cylinder was dropping off-line on the right mag. The
>left mag was normal.
>
>No amount of high RPM leaning would clear it, so back to the hangar we
>went. Pulled the cowling, and the #2 cylinder spark plugs. No
>fouling was noted, but I cleaned the plugs anyway, and reinstalled
>them. I also probed the wiring, wiggling and checking for loose
>connections. None were noted.
>
>After reassembly, everything ran normally, and passed the mag checks.
>I took Atlas around the patch, and all was well. WTF?
>
>Some thoughts:
>
>1. Since 2004 we have switched to the high-dollar Iridium plugs. As
>stated, no fouling was noted, so I don't think the plugs are to blame.
>
>2. Is it possible that the #2 cylinder spark plug wires are shorting
>internally due to all the moisture in the air? Has anyone ever heard
>of this happening?
>
>3. Is it more likely that the mag itself would be affected by the
>moisture? Has anyone ever heard of this?
>
>The fact that this happened three years apart, in very similar weather
>conditions, on the same cylinder, has me deeply suspicious. I'm
>thinking that maybe de-cowling the plane and letting it sit in the
>breeze (thereby drying out whatever moisture may be shorting the #2
>cylinder's right-mag plug) actually helped to solve the problem more
>than anything I actively accomplished by pulling the plugs.
>
>Any ideas here, folks? What could cause this, and what's the fix?

[Jay Honeck]

> When the engine warms up and sits during plug cleaning the engine heat
> drys out the water in the magneto and/or the plug wire. Result is the
> problem is gone. I would test the spark plug with a pressure test to
> make sure it is not internally cracked and will fire under pressure
> and I would also high voltage test the plug wire or just replace that
> wire. Also inspect the distrubitor in the mag for carbon tracks.

Thanks, John. My A&P and I are going to check all that out
tomorrow.

Incidentally, I've noticed a wide variation in pricing on new spark
plug wiring, ranging from ~$170 to >$300. This is a HUGE variation,
for something so mundane -- can anyone comment on why this is?

My A&P is partial to the Unison ("Slick") brand, which is over $300.
He says they are more expensive because each piece can be easily
individually replaced, whereas the cheaper brands just "crimp"
everything together, making them harder to repair.

Can anyone recommend (or steer me away from) a brand?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Brock Boss]

On Apr 4, 6:37 pm, "Jay Honeck" > wrote:

> Can anyone recommend (or steer me away from) a brand?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993www.AlexisParkInn.com
> "Your Aviation Destination"

Jay,

Mike Busch and lots of members of the Cessna Pilots Assoc. recommend
the Unison/Slick harnesses whether you have Slick mags or Bendix. They
say the wires on the Slick harnesses are more flexible and the
"cigarettes" are better as well. I have no experience either way, just
thought I'd pass along what I've read on the CPA forums.


Brock Boss
3916R - KAAA

[Viperdoc[_4_]]

I think it still could be a bad plug- my understanding is that they can look
good while still being weak under a load- did you check it in one of those
fancy spark plug testers?

It seems to me a simple test would be to swap two plugs- it the problem
remained with the "new" plug, then the problem likely would lie in the
harness.

[Denny]

>
> Can anyone recommend (or steer me away from) a brand?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993www.AlexisParkInn.com
> "Your Aviation Destination"

Well, Slick's are slick but the devil is in the details.. When Fat
Albert needed the mags spiffed up I elected to replace them totally
over just replacing parts... I looked at the Slicks and really like
them... But, a grizzled and really old A&P, name of Bill, looked at
me, rolled his cigarette from one side of his mouth to the other and
said, "Check and see if anyone can fix a Slick magneto, right today.
Tell em you gotta fly home tonight" (This was 10AM on December
24th)... Then he gave me that evil grin he is known for...
So I whipped out my trusty cellphone and called three different FBO's
in Michigan... Nobody had parts for a Slick but they all had most
parts for Bendix and one even said he had the adapter for the Slick
harness and could put a Bendix magneto together for me that would work
and get me home..
I bought 4 rebuilt Bendix mags... The Fat Boy starts like he is a
teenager again... And I know that if they break down almost any FBO
will have parts on hand...

denny

[Jay Honeck]

On Apr 4, 6:17 pm, "Viperdoc" > wrote:
> I think it still could be a bad plug- my understanding is that they can look
> good while still being weak under a load- did you check it in one of those
> fancy spark plug testers?
>
> It seems to me a simple test would be to swap two plugs- it the problem
> remained with the "new" plug, then the problem likely would lie in the
> harness.

We'll check that later today, but it seems unlikely that it's the
plug, since it's been replaced in between occurences, and it *still*
happened on the same cylinder, same plug position.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Jay Honeck]

> Well, Slick's are slick but the devil is in the details..

Thanks, Denny -- but I'm only replacing the spark plug wiring harness
at this point.

I hope!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Jay Honeck]

> Well, Slick's are slick but the devil is in the details..

The fix is in: Atlas does have a Slick harness, and my A&P has all the
pieces/parts to craft a new spark plug wire for our #2 cylinder, from
the right mag.

This will save me approximately $250, and should fix the problem. He
said he'll have it done before we leave for SNF.

He inspected the harness, and could find no reason to replace the
entire thing, as there were only normal signs of age.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"