Today's Message Index:
----------------------
1. 05:18 AM - Re: intermittent idle problem (Gary Casey)
2. 10:20 AM - Re: LycomingEngines-List Digest: 1 Msgs - 06/15/07 (Paul Millner [OAK])
3. 02:49 PM - (MASON CHEVAILLIER)
4. 09:04 PM - Re: Re: LycomingEngines-List Digest: 1 Msgs - 06/15/07 (Dave Lammers)
Message 1
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| Subject: | Re: intermittent idle problem |
It sounds very much like the "normal" hot fuel handling problem with
the fuel system. Vapor can form in several locations and I think Don
has correctly diagnosed the problem - fuel vapor downstream of the
fuel servo. Symptom will be that after a hot start the engine will
intermittently "quit" and if the speed is too low it might not
recover. Increasing engine speed will mask it. Since there is no
return line the vapor has to go through the injectors, but if it were
downstream of the flow divider it is likely that only one cylinder
would have the problem. The most effective method of reducing the
problem (a complete cure is probably not practical) is to insulate
all the fuel lines in the engine compartment, paying special
attention to the line between the servo and the flow divider. For
that reason I always use lines with the loose (red) firesleeve. That
makes a better insulator than the integral firesleeve lines you can
buy. If you have such a line in that location you can always add the
loose sleeve over the other one. The "stiffer" spring in the flow
divider will hold a higher pressure in the system when the engine is
shut off, tending to suppress vaporization - a good thing.
It shouldn't have that problem on a cold startup unless the fuel is
leaking back through the system, which I suppose is possible if it is
shut down for days or weeks.
Gary Casey
>
> Greetings experts...
>
> Recently purchased an RV6 (1994-98 build) with a (H)IO-360 engine
> -- '95
> vintage Airflow Performance (Bendix) injection system/Performance
> Propeller cruise prop (wood w/ damper) and dual Electroair ignition.
> Performs beautifully... almost all the time. I have an intermittent
> idle issue. It's not a typical rough idle, but when the problem shows
> itself it's as if the ignition is turned off, then immediately back
> on,
> i.e., smooth idle for several seconds, abrupt pause, smooth
> idle...abrupt pause...etc. Seems to occur more often with a hot
> engine,
> though it's cropped up a few times on initial start-up. The
> problem has
> been consistent with the engine from day one... almost 300 tach hours.
>
> Troubleshooting so far:
> - replaced one electronic ignition system with a mag... no change.
> -wrapped exhaust system and installed heat shield between exhaust
> and fuel control... n/c.
> -checked all O-rings/connections for possible air leak...n/c
> -installed 0.22 injector nozzles to increase pressure
> downstream of
> flow divider... n/c.
>
> Other things that seem to have no effect:
> -electric boost pump on/off
> -direct air intake or alternate
> -leaning
>
> One thing that sometimes clears the problem: 1800-2000 rpm for 30-45
> seconds.
>
> Don, at Airflow Performance, is convinced I'm vaporizing gas
> downstream
> of the flow divider, but so far no fix. He has recently set me a
> 'stiffer' spring for the flow divider. I've installed same and flown
> the aircraft a couple of times with no problems, but I've often flown
> 2-3 times in a row with no problems, so the jury is still out as to
> this
> being "the" fix.
>
> Anybody have a suggestion/theory/similar experience?
>
> Dennis
> Virginia Beach
Message 2
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| Subject: | Re: LycomingEngines-List Digest: 1 Msgs - 06/15/07 |
I can't see how a stiffer spring for the flow divider would help when
you WANT the engine to run... that should help prevent the engine from
dieseling after hot shutoff.
That said, I don't know why your fuel system might be hesitating... if
it is.
Paul
LycomingEngines-List Digest Server wrote:
> *
>
> =================================================
> Online Versions of Today's List Digest Archive
> =================================================
>
> Today's complete LycomingEngines-List Digest can also be found in either of the
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> in HTML for viewing with a web browser and features Hyperlinked Indexes
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> such as Notepad or with a web browser.
>
> HTML Version:
>
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>
> Text Version:
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>
>
> ===============================================
> EMail Version of Today's List Digest Archive
> ===============================================
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>
> ----------------------------------------------------------
> LycomingEngines-List Digest Archive
> ---
> Total Messages Posted Fri 06/15/07: 1
> ----------------------------------------------------------
>
>
> Today's Message Index:
> ----------------------
>
> 1. 04:28 PM - intermittent idle problem (Dennis Holbrook)
>
>
>
> ________________________________ Message 1 _____________________________________
>
>
> Time: 04:28:23 PM PST US
> From: "Dennis Holbrook" <dholbrook7@COX.NET>
> Subject: LycomingEngines-List: intermittent idle problem
>
> Greetings experts...
>
> Recently purchased an RV6 (1994-98 build) with a (H)IO-360 engine -- '95
> vintage Airflow Performance (Bendix) injection system/Performance
> Propeller cruise prop (wood w/ damper) and dual Electroair ignition.
> Performs beautifully... almost all the time. I have an intermittent
> idle issue. It's not a typical rough idle, but when the problem shows
> itself it's as if the ignition is turned off, then immediately back on,
> i.e., smooth idle for several seconds, abrupt pause, smooth
> idle...abrupt pause...etc. Seems to occur more often with a hot engine,
> though it's cropped up a few times on initial start-up. The problem has
> been consistent with the engine from day one... almost 300 tach hours.
>
> Troubleshooting so far:
> - replaced one electronic ignition system with a mag... no change.
> -wrapped exhaust system and installed heat shield between exhaust
> and fuel control... n/c.
> -checked all O-rings/connections for possible air leak...n/c
> -installed 0.22 injector nozzles to increase pressure downstream of
> flow divider... n/c.
>
> Other things that seem to have no effect:
> -electric boost pump on/off
> -direct air intake or alternate
> -leaning
>
> One thing that sometimes clears the problem: 1800-2000 rpm for 30-45
> seconds.
>
> Don, at Airflow Performance, is convinced I'm vaporizing gas downstream
> of the flow divider, but so far no fix. He has recently set me a
> 'stiffer' spring for the flow divider. I've installed same and flown
> the aircraft a couple of times with no problems, but I've often flown
> 2-3 times in a row with no problems, so the jury is still out as to this
> being "the" fix.
>
> Anybody have a suggestion/theory/similar experience?
>
> Dennis
> Virginia Beach
>
>
>
>
>
>
>
>
>
Message 3
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please unsubscribe me from this list. I wish to stay on the commander
list. thank you
Message 4
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| Subject: | Re: LycomingEngines-List Digest: 1 Msgs - 06/15/07 |
Paul,
The stiffer spring makes the fuel servo have to "push" harder to get the
fuel into the flow divider. Remember, the system is a closed loop
system. The servo measures how much air is coming through the throat of
the servo, then meters the correct proportion of fuel (to match that
much air) and sends it up to the flow divider which distributes the fuel
to the cylinders. The stiffer the spring, the harder it has to push on
the fuel to get that correct flow (up to the limit of its input pressure
which is the output pressure of the fuel pump usually around 22 psi.).
This increased "push" increases the pressure in the fuel line between
the servo and the flow divider. It is this line which is usually the
culprit with regard to heat causing fuel vaporization bubbles which lead
to the hesitating reported by Dennis. The increased pressure within
this line will increase the temperature at which vaporization will
begin. The old PV=nRT equation. Hopefully, the spring will cause the
pressures to increase such that the temperature for onset of
vaporization is higher than the temperature in his particular
installation at the low fuel flows (i.e. = to low fuel pressures out of
the servo). If that happens, Dennis will report that this if fact was
the "fix" his post discussed.
For Dennis,
I had a very similar problem. Most of the problem went away with the
stiffer spring. However, some symptoms remain on very warm days or long
taxis on warm days. I have talked to several others with similar
problem. A common factor is light weight wood propellors. It seems
they do not have enough inertia to carry the engine through these very
brief "burps" without the pilot noticing. It is theorized that the much
much heavier metal props have enough inertia to make these symptoms not
noticeable on those aircraft, but that, in fact, the same thing is going
on, but because of the extra prop inertia, the pilot senses "just a
rough running mag" at idle, or something of that sort. My guess is that
most of your problem will go away with the stiffer spring. Good luck!!
Regards,
Dave Lammers
Paul Millner [OAK] wrote:
> <paulmillner@compuserve.com>
>
> I can't see how a stiffer spring for the flow divider would help when
> you WANT the engine to run... that should help prevent the engine from
> dieseling after hot shutoff.
>
> That said, I don't know why your fuel system might be hesitating... if
> it is.
>
> Paul
>
> LycomingEngines-List Digest Server wrote:
>
>> *
>>
>> =================================================
>> Online Versions of Today's List Digest Archive
>> =================================================
>>
>> Today's complete LycomingEngines-List Digest can also be found in
>> either of the two Web Links listed below. The .html file includes
>> the Digest formatted in HTML for viewing with a web browser and
>> features Hyperlinked Indexes and Message Navigation. The .txt file
>> includes the plain ASCII version of the LycomingEngines-List Digest
>> and can be viewed with a generic text editor such as Notepad or with
>> a web browser.
>> HTML Version:
>>
>>
>> http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter 07-06-15&Archive=LycomingEngines
>>
>>
>> Text Version:
>>
>>
>> http://www.matronics.com/digest/digestview.php?Style=82701&View=txt&Chapter 07-06-15&Archive=LycomingEngines
>>
>>
>>
>> ===============================================
>> EMail Version of Today's List Digest Archive
>> ===============================================
>>
>>
>> ----------------------------------------------------------
>> LycomingEngines-List Digest Archive
>> ---
>> Total Messages Posted Fri 06/15/07: 1
>> ----------------------------------------------------------
>>
>>
>> Today's Message Index:
>> ----------------------
>>
>> 1. 04:28 PM - intermittent idle problem (Dennis Holbrook)
>>
>>
>>
>> ________________________________ Message 1
>> _____________________________________
>>
>>
>> Time: 04:28:23 PM PST US
>> From: "Dennis Holbrook" <dholbrook7@COX.NET>
>> Subject: LycomingEngines-List: intermittent idle problem
>>
>> Greetings experts...
>>
>> Recently purchased an RV6 (1994-98 build) with a (H)IO-360 engine --
>> '95 vintage Airflow Performance (Bendix) injection system/Performance
>> Propeller cruise prop (wood w/ damper) and dual Electroair
>> ignition. Performs beautifully... almost all the time. I have an
>> intermittent idle issue. It's not a typical rough idle, but when the
>> problem shows itself it's as if the ignition is turned off, then
>> immediately back on, i.e., smooth idle for several seconds, abrupt
>> pause, smooth idle...abrupt pause...etc. Seems to occur more often
>> with a hot engine, though it's cropped up a few times on initial
>> start-up. The problem has been consistent with the engine from day
>> one... almost 300 tach hours.
>> Troubleshooting so far:
>> - replaced one electronic ignition system with a mag... no change.
>> -wrapped exhaust system and installed heat shield between exhaust
>> and fuel control... n/c.
>> -checked all O-rings/connections for possible air leak...n/c
>> -installed 0.22 injector nozzles to increase pressure downstream
>> of flow divider... n/c.
>>
>> Other things that seem to have no effect:
>> -electric boost pump on/off
>> -direct air intake or alternate
>> -leaning
>>
>> One thing that sometimes clears the problem: 1800-2000 rpm for 30-45
>> seconds.
>>
>> Don, at Airflow Performance, is convinced I'm vaporizing gas
>> downstream of the flow divider, but so far no fix. He has recently
>> set me a 'stiffer' spring for the flow divider. I've installed same
>> and flown the aircraft a couple of times with no problems, but I've
>> often flown 2-3 times in a row with no problems, so the jury is still
>> out as to this being "the" fix.
>>
>> Anybody have a suggestion/theory/similar experience?
>>
>> Dennis
>> Virginia Beach
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
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