mysterious fuel leak

[glider_rider]

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

[Bdflies]

Originally Posted by glider_rider

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, I’m going to have a close look at mine.

Bill

[glider_rider]

#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.

[Bdflies]

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 it’s much better. Flying, it’s 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 don’t know for sure.
By the way, my #2 injector looks very similar to yours!

[Taltruda]

Originally Posted by glider_rider

#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 isn’t saying much.. Lycoming redline of 500*F is crazy.. most people consider 420 to 430 a more realistic limit..

[glider_rider]

#2 CHT is ca. 340-350 while other ones are 10 deg cooler

[Avanza]

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

[rvbuilder2002]

Originally Posted by Avanza

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.

[lr172]

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.

[glider_rider]

Originally Posted by rvbuilder2002

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?