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  #1  
Old 02-14-2023, 07:52 AM
glider_rider glider_rider is offline
 
Join Date: Aug 2020
Location: Poland
Posts: 27
Default mysterious fuel leak

I'm having a hard time to find a root cause of leak from injector on cyl 2 on my IO-390 EXP 119. I'm pretty sure the injector is installed and torqued properly. The A letter mark is on the bottom side.
Did a quick test: removed the cowling and covered the injector with a piece of cloth, then run the engine for a few minutes. The cloth was dry, which would suggest that on the ground the injector doesn't leak. Nevertheless after a few hours of flight traces of fuel indicate that something is seriously wrong.
Is it possible that somehow fuel is sucked out of the injector's screen?
thanks in advance for any help
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  #2  
Old 02-16-2023, 10:40 AM
Bdflies Bdflies is offline
 
Join Date: Nov 2021
Location: Louisiana
Posts: 19
Default Letís talk about this

Quote:
Originally Posted by glider_rider View Post
I'm having a hard time to find a root cause of leak from injector on cyl 2 on my IO-390 EXP 119. I'm pretty sure the injector is installed and torqued properly. The A letter mark is on the bottom side.
Did a quick test: removed the cowling and covered the injector with a piece of cloth, then run the engine for a few minutes. The cloth was dry, which would suggest that on the ground the injector doesn't leak. Nevertheless after a few hours of flight traces of fuel indicate that something is seriously wrong.
Is it possible that somehow fuel is sucked out of the injector's screen?
thanks in advance for any help
How do the EGT's and CHT's look? Fuel flow at 75%, 100 ROP? Does the engine run well, without erratic misfires?

In the meantime, Iím going to have a close look at mine.

Bill
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  #3  
Old 02-16-2023, 12:38 PM
glider_rider glider_rider is offline
 
Join Date: Aug 2020
Location: Poland
Posts: 27
Default

#2 is the hottest cylinder, but CHT stay well below Lycoming's red line.
The engine does indeed run somewhat erratic on low rpm, say below 1000 rpm, but on the other hand flat out I can easily exceed 190 knots. On high rpm the engine runs like a Swiss watch.
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  #4  
Old 02-18-2023, 07:45 PM
Bdflies Bdflies is offline
 
Join Date: Nov 2021
Location: Louisiana
Posts: 19
Default

When new, mine was a little rich at idle and ran noticeably rough. Aggressive leaning helped and I adjusted idle mixture on the servo. I still lean on the ground, but itís much better. Flying, itís smooth and strong. #2 is the hottest, by a little, on mine as well. I have some theories about the residue around the injector, but donít know for sure.
By the way, my #2 injector looks very similar to yours!
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  #5  
Old 02-18-2023, 08:39 PM
Taltruda Taltruda is offline
 
Join Date: Oct 2017
Location: Las Vegas, NV
Posts: 1,517
Default

Quote:
Originally Posted by glider_rider View Post
#2 is the hottest cylinder, but CHT stay well below Lycoming's red line.
The engine does indeed run somewhat erratic on low rpm, say below 1000 rpm, but on the other hand flat out I can easily exceed 190 knots. On high rpm the engine runs like a Swiss watch.
CHTs well below Lycoming redline isnít saying much.. Lycoming redline of 500*F is crazy.. most people consider 420 to 430 a more realistic limit..
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  #6  
Old 02-18-2023, 11:55 PM
glider_rider glider_rider is offline
 
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Location: Poland
Posts: 27
Default

#2 CHT is ca. 340-350 while other ones are 10 deg cooler
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  #7  
Old 02-19-2023, 05:43 AM
Avanza Avanza is offline
 
Join Date: Jul 2020
Location: Vastervik Sweden
Posts: 315
Smile

I would clean the area close to the injector.
My two cents, this happens on GND after fuel cut off.
It could be fuel left in the divider and heat push whats left there.
Try to run 1,000 rpm and then pull mixture.

Good luck
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  #8  
Old 02-21-2023, 11:12 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 10,137
Default

Quote:
Originally Posted by Avanza View Post
I would clean the area close to the injector.
My two cents, this happens on GND after fuel cut off.
It could be fuel left in the divider and heat push whats left there.
Try to run 1,000 rpm and then pull mixture.
Possibly...
Or it could be from air disturbance from the air blast directed onto the injector.

The left side front air dam supplied with the baffle kit has a block out area located directly in front of the #2 injector. I see that you do not have the dam installed (though maybe you removed it to take the photo?)
I think it would help with this.
The company prototypes have the air dam trimmed down somewhat but the portion that is in front of the injector body is left full height.
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Hubbard, Oregon
Formerly of Van's Aircraft Engineering Prototype Shop
FAA/DAR, EAA Technical Councelor
RV-6A (aka "Junkyard Special ")
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  #9  
Old 02-21-2023, 12:32 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Default

could be normal. At shut down after a flight, the under cowl temps get pretty hot. The fuel in the SS lines boil and this pushes the fuel towards the injector. Can't go the other way due to ICO. Most of it goes past the restrictor, but some does go out of the vent screen.
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Last edited by lr172 : 02-21-2023 at 12:37 PM.
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  #10  
Old 02-21-2023, 02:25 PM
glider_rider glider_rider is offline
 
Join Date: Aug 2020
Location: Poland
Posts: 27
Default

Quote:
Originally Posted by rvbuilder2002 View Post
Possibly...
Or it could be from air disturbance from the air blast directed onto the injector.

The left side front air dam supplied with the baffle kit has a block out area located directly in front of the #2 injector. I see that you do not have the dam installed (though maybe you removed it to take the photo?)
That's exactly right, I removed the air dam to take a better shot at the fuel residue
As cylinder #2 is the hottest one, I was thinking about trimming the air dam just a little bit to let the ram air around that last fin. Is it good idea?
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