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12-29-2012, 10:40 AM
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Join Date: Oct 2005
Posts: 1,516
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Black gooo?
What is the black goo?
Has your proseal become soft?
Have you run mogas in both tanks?
How many years on mogas?
Glad you found the "apparent" problem but I would search a little further too.
__________________
Ernst Freitag
RV-8 finished (sold)
RV-10 Flyer 600 plus hours
Running on E10 mogas
Don't believe everything you know.
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12-29-2012, 11:33 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Returning to the original issue.....I'll put my money on a partially blocked injector orifice.
This is the previous EIS graphic, stripped of everything except #2 EGT and fuel flow:
The cylinder runs fine (EGT is normal) below fuel flows of around 4 GPH. At 5 GPH it's going too lean, and at 6 or more it can't light. Put another way, the blockage is (was) limiting #2 fuel flow to about 1 GPH (1/4 of 4 GPH), which is fine at low air flow, but additional air (manifold pressure requiring more than 1GPH) just makes it too lean to run.
I asked Steve about checking the Bendix servo inlet screen because it incorporates an interesting detail. Fuel is delivered to the inner bore of the screen. The screen is held against the inlet fitting with a very light spring. If the trash load gets too high fuel pressure pushes the finger screen away from the inlet fitting during a period of high required fuel flow, allowing fuel to bypass the screen. That's good given the alternative (no or reduced fuel flow), but when it happens a clump of collected trash often escapes downstream into the servo, divider, and/or injector(s). That's how trash gets to an injector despite the upstream screens.
It's a small, very fine screen, easy to restrict, in particular if any kind of goo comes down the line. The Bendix literature says it should be cleaned every 50 hours. I'd bet most are not cleaned anywhere near that often. When you do clean one, remove it from the inlet fitting end, not the plug end, again so you don't spill collected trash into the screen bore.
Cleaning injectors: You really need a magnifier to examine injector bores, 10x minimum. Here's my long term favorite; I've even shot photos through it:
http://www.grainger.com/Grainger/BAU...agnifier-3G993
Scott, can you tell us a little more about what you found on the inner bore of the inlet screen? Fiberglass hair eh? Any of the black goo too?
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 12-29-2012 at 01:19 PM.
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12-29-2012, 11:57 AM
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Join Date: Jan 2008
Location: KTCY
Posts: 643
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Quote:
Originally Posted by Walt
The AFP filter is 125 micron so it's not an overly fine unit, I prefer to use a 74 micron unit.
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Keeping in mind that if the filter gets plugged ... all cylinders go to sleep
Quote:
Originally Posted by DanH
Returning to the original issue.....I'll put my money on a partially blocked injector orifice.
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Blockage somewhere ...
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Dave & Trina
RV-9A Flying  - 330 Hrs. Painted  Finishing the interior.
Last edited by MauiLvrs : 01-02-2013 at 07:37 PM.
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12-29-2012, 01:16 PM
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Join Date: Jan 2005
Location: Battle Ground, Washington
Posts: 138
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Check fuel distribution manifold
A blockage effecting a single cylinder can occur anywhere from the fuel distribution manifold to the injector. I would open and inspect the distribution manifold for foreign debris. I had this happen to a new IO-360M1 with similar symptoms to yours. In my case, the blockage would occasionally move around in the fuel distribution manifold, sometimes effecting a different cylinder and sometimes effecting none. Very frustrating to trouble check.
Dan Miller
RV-8
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12-29-2012, 01:20 PM
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Join Date: Nov 2005
Location: Davis, CA
Posts: 1,156
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Quote:
Originally Posted by DanH
Cleaning injectors: You really need a magnifier to examine injector bores, 10x minimum.
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Agree in principle- I used my own 10x lighted eye loupe to examine mine, but I'm gonna guess that a particle big enough to reduce fuel flow by a factor of roughly 4 will be visible to the naked eye.
Also worth doing a flow test since it's so easy. 4 baby food jars work great- everyone has baby food jars in their hangar, right?
__________________
Lars Pedersen
Davis, CA
RV-7 Flying as of June 24, 2012
960+ hours as of June 30, 2020. Where did the time go?
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12-29-2012, 02:45 PM
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Join Date: Jan 2005
Location: Marion IA
Posts: 1,095
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picture of bendix inlet screen?
Quote:
Originally Posted by DanH
It's a small, very fine screen, easy to restrict, in particular if any kind of goo comes down the line. The Bendix literature says it should be cleaned every 50 hours. I'd bet most are not cleaned anywhere near that often. When you do clean one, remove it from the inlet fitting end, not the plug end, again so you don't spill collected trash into the screen bore.
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Does anyone have a picture of this screen assembly, and how it comes out? I don't understand the part about "remove from inlet fitting end, not the plug end"
Thanks!
__________________
Dave Gribble VAF #232
Building RV-9A N149DG (slider, IO-320, IFR)
Restored and Flying Beech Super III N3698Q
Marion IA
Struggling with fiberglass
There is no sport equal to that which aviators enjoy while being carried through the air on great white wings." Wilbur Wright, 1905
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12-29-2012, 03:48 PM
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Join Date: Feb 2006
Location: San Diego, CA, U.S.A.
Posts: 770
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Quote:
Originally Posted by IowaRV9Dreamer
Does anyone have a picture of this screen assembly, and how it comes out? I don't understand the part about "remove from inlet fitting end, not the plug end"
Thanks!
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The fuel inlet part of the throttle body is bored all the way through from left to right, and is threaded on both ends. You can choose which side you want the fuel inlet fitting to be on for your specific installation. So you thread the inlet fitting into the side you choose (and orient the inlet screen accordingly), and you thread a plug into the opposite side.
So, about removing the inlet screen for cleaning, as others said, you want to remove it by removing the inlet fitting, not the plug on the opposite side.
Documentation from Precision Airmotive:
http://precisionairmotive.com/Publications/25-020_a.pdf
See section 6.2 (pg 3), and drawings on page 8.
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12-29-2012, 03:57 PM
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Join Date: Oct 2008
Location: Arlington, WA
Posts: 799
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Quote:
Originally Posted by cdmiller
A blockage effecting a single cylinder can occur anywhere from the fuel distribution manifold to the injector. I would open and inspect the distribution manifold for foreign debris. I had this happen to a new IO-360M1 with similar symptoms to yours. In my case, the blockage would occasionally move around in the fuel distribution manifold, sometimes effecting a different cylinder and sometimes effecting none. Very frustrating to trouble check.
Dan Miller
RV-8
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Yep! Great suggestion. The spider (fuel distribution manifold) is off the engine and getting opened and cleaned today. I'll let you know what I find.
PS. The spider (according to my engine guru) is very, very, very susceptible to any impurities, and also to any mis-handling. So much so, that he asked that I deliver it to him un-opened. He'll open and clean it.
PPS. It's also expensive to replace if damaged!
__________________
_______________________________
Scott "Grumpy" Stewart
RV-7 N957RV (First Flight on Dec 18, 2009 )
RV-14 N144P (Empennage complete, wings almost complete, fuselage almost complete)
#866 on the Van's RV-7 hobbs
#6563 on Van's generic hobbs
Arlington, WA
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12-29-2012, 04:55 PM
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Join Date: Jan 2005
Location: Battle Ground, Washington
Posts: 138
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Spider sensitive
Grumpy,
I didn't open and mess with my spider either. I sent it back to Bart at AeroSport Power and he found the debris and removed it. I think he said it was metal cutting(s) that could move around in the spider and cause partial blockage to a cylinder. No problems in hundreds of hours since.
Dan Miller
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12-29-2012, 06:12 PM
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Join Date: Jun 2005
Posts: 693
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Here's something you might want to evaluate. I haven't used it yet, but looks interesting. https://www.savvyanalysis.com/home
The graphing stuff is free, and for a fee they will do some analysis. Mike Busch does an interesting presentation at OSH about reading engine data and how to interpret it.
__________________
Marc Ausman
RV-7 980 hours, IO-390, VP-X (sold)
RV-8 (flying a friend's)
Thinking about low and slow backcountry build.
VAF Advertiser - Aircraft Wiring Guide
Book to help with experimental aircraft wiring.
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