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gary_eady(at)xtra.co.nz Guest
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Posted: Thu Feb 06, 2014 11:19 pm Post subject: Rough running Jab 3300 |
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I'm having a few issues with my Jab 3300 solid lifter engine. Intermittently, normally under load in the climb, it develops a miss in either one or other of the front cylinders. The miss/rough running only lasts between about 10 and 20 seconds and recurs every couple of hours or so of flying - but is enough to make me look around quickly for an off field landing area.
Have checked the resistance and condition of the HT leads and also the coils. All seem to be ok.
The errant cylinder is easy to track via the EGT probes and is always number 1 or 2 which is suddenly about 100 degrees C cooler than the others.
The engine has 70 hours on it and starts well hot or cold - is burning no oil and throws virtually no oil into the breather bottle. All engine parameters are great including cylinder head temps. Except for this darn miss.
Anyone else out there having or had a similar problem??
Regards
Gary
CH701, Jab 3300A serial number 500, 70 hours total time. Grand Rapids EIS.
[quote][b]
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psm(at)att.net Guest
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Posted: Thu Feb 06, 2014 11:36 pm Post subject: Rough running Jab 3300 |
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Hi Gary,
First let me say I am no expert on engines of any sort. So don't depend on my being right.
I once had some strange miss-firing because the carburetor was loose. It was more dramatic than your story and only went bad when I reduced to idle power for descent.
The thing that comes to mind listening to your story is you are at a high angle of attack. That suggests there is something about the air flow to the carburetor might be funny. In my plane I took extra measures to straighten out the air flow just in front of the carburetor. There are several ways to do this, and I don't really know if any are necessary.
A 3300 is a large engine for a 701. You must get very high pitch on the aircraft nose when climbing. This suggests a possible problem with fuel pressure could be involved. Do you have a boost pump?
Good luck,
Paul
Camas, WA
Zodiac XL, Jab 3300
On 2/6/2014 11:16 PM, Gary Eady wrote:
[quote] I'm having a few issues with my Jab 3300 solid lifter engine. Intermittently, normally under load in the climb, it develops a miss in either one or other of the front cylinders. The miss/rough running only lasts between about 10 and 20 seconds and recurs every couple of hours or so of flying - but is enough to make me look around quickly for an off field landing area.
Have checked the resistance and condition of the HT leads and also the coils. All seem to be ok.
The errant cylinder is easy to track via the EGT probes and is always number 1 or 2 which is suddenly about 100 degrees C cooler than the others.
The engine has 70 hours on it and starts well hot or cold - is burning no oil and throws virtually no oil into the breather bottle. All engine parameters are great including cylinder head temps. Except for this darn miss.
Anyone else out there having or had a similar problem??
Regards
Gary
CH701, Jab 3300A serial number 500, 70 hours total time. Grand Rapids EIS.
[b]
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zeprep251(at)aol.com Guest
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Posted: Fri Feb 07, 2014 8:53 am Post subject: Rough running Jab 3300 |
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Gary,my first thought would be carb ice.Any way of determining air temp or humidity during these episodes?Do you have any carb heat provisions or alternate air intake possibilities? G.Aman Kolb MK3 Jabiru 900 hrs
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UK Clive
Joined: 17 May 2013 Posts: 27
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Posted: Fri Feb 07, 2014 9:31 am Post subject: Rough running Jab 3300 |
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Does it do it if you throttle back a tad?
[quote] On 7 Feb 2014, at 16:52, Gary Aman <zeprep251(at)aol.com> wrote:
Gary,my first thought would be carb ice.Any way of determining air temp or humidity during these episodes?Do you have any carb heat provisions or alternate air intake possibilities?
G.Aman Kolb MK3 Jabiru 900 hrs
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UK Clive
Joined: 17 May 2013 Posts: 27
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Posted: Fri Feb 07, 2014 9:40 am Post subject: Rough running Jab 3300 |
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Carby ice doesn't occur at wot.....
[quote] On 7 Feb 2014, at 16:52, Gary Aman <zeprep251(at)aol.com> wrote:
Gary,my first thought would be carb ice.Any way of determining air temp or humidity during these episodes?Do you have any carb heat provisions or alternate air intake possibilities?
G.Aman Kolb MK3 Jabiru 900 hrs
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BARRY CHECK 6
Joined: 15 Mar 2011 Posts: 738
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Posted: Fri Feb 07, 2014 11:17 am Post subject: Rough running Jab 3300 |
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Carb Ice sure can occur at WOT and even on a 70 F day.
http://flighttraining.aopa.org/students/presolo/skills/carbicing.html
On Fri, Feb 7, 2014 at 12:38 PM, Clive james <zcrj90(at)yahoo.co.uk (zcrj90(at)yahoo.co.uk)> wrote:
[quote]Carby ice doesn't occur at wot.....
On 7 Feb 2014, at 16:52, Gary Aman <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:
[quote]Gary,my first thought would be carb ice.Any way of determining air temp or humidity during these episodes?Do you have any carb heat provisions or alternate air intake possibilities? G.Aman Kolb MK3 Jabiru 900 hrs
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n5pb(at)aol.com Guest
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Posted: Fri Feb 07, 2014 2:28 pm Post subject: Rough running Jab 3300 |
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I've experienced carb icing in Clearwater, FL the last couple of summers. When it last happened I applied carb heat on continuously during landing and TAKEOFF on consecutive touch and go's. With the carb heat on I experenced No further issues. With that in mind, I installed the electric carburator heat assembly that jabiru USA sells. This gave me the carb heat needed, but did not reduce engine efficiency. so far i've not had any similiar issues.
I did a write up on the installation and should be out with the next newsletter.
Bear
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Gary Eady
Joined: 17 Feb 2014 Posts: 1
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Posted: Mon Feb 17, 2014 11:31 am Post subject: Re: Rough running Jab 3300 |
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Thanks guys. I flew 2 hours non-stop last weekend and left one element of the electric ice eliminator on at all times. No rough running problems so assuming the problem was icing.
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