Although I agree with your assessment of over thinking this situation, I am amused at the thought of you saying something about over thinking.
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Fuel leak around plug
- Thread starter scorwin
- Start date
Rdog420
Active Member
I'd just replace that line at this point, clean the blue stains so you have a good plain cylinder. Then do some ground runs with the new line and see if that blue residue stops accumulating, and your EGT/ CHT normalize. I don't see another scenario that would cause your problem.
scorwin
Active Member
Had 2 separate A&P come out. Look at it. Both cleaned out injector. Line was pressure tested, no leaks found. Both A&P rec flying the plane. Had Savvy look over the data, after a couple of back/forth messages they said the same.
"Having an A&P thoroughly work over this part of the fuel system seems to be the best answer, but it seems like that was already done. If the A&P has approved the aircraft for return to service, suggest flying it more to see if the readings stabilize."
3 separate ground runs on different days unable to reproduce anything.
So will be flying it later today with an instructor for an extra set of eyes. Will be staying close to the airport for a while. Will update after a flight or 2 as well
I would highly recommend that you check valve guide clearances.
So, what did the mechanics attribute all the fuel staining to? If something spit out several ounces of fuel and you did nothing to identify the source, what leads you to believe it won’t happen again? It is certainly possible that someone inadvertently addressed the issue with all of the hands on it, but I would watch that like a hawk! Not finding a cause for a problem is one of the most upsetting events for a mechanic or owner, as you have no idea if the issue will return or not.
A more rare possibility is backfiring. This creates positive pressure in the cyl intake chamber and will blow fuel out of the injector vent. Was this considered or explored?
It's clear to me that fuel did not leak from a spark plug or bushing for reasons pointed out by others.
I am also quite convinced that there is not a leak coming from the injector line or injector body.
If there was, it surely would have some left traces of blue stains around the fitting or base of the injector and the surrounding area.
That area is clean without a trace of stain, highly unlikely in this very turbulent area of the plenum. If there was a leak from the injector lines or fitting, we would see spray pattern stains everywhere not just neatly flowing stains down the push rod shroud and a bit of the cylinder fins.
The stain maybe from someone doing a flow test and spilling fuel or something of that nature. Did you build the plane?
I'd start looking at your ignition and electrical system. The fact that your #5 cht/egt info went "blank" for a bit sounds indicative of an electrical problem.
I would definitely heed the advice of previous posters, test the lines, clean up the fuel stain (fuel works great for cleanup of blue stains) and if you do go up and fly, see if that fuel stain returns.
I am betting my money on something other than a fuel leak
I am also quite convinced that there is not a leak coming from the injector line or injector body.
If there was, it surely would have some left traces of blue stains around the fitting or base of the injector and the surrounding area.
That area is clean without a trace of stain, highly unlikely in this very turbulent area of the plenum. If there was a leak from the injector lines or fitting, we would see spray pattern stains everywhere not just neatly flowing stains down the push rod shroud and a bit of the cylinder fins.
The stain maybe from someone doing a flow test and spilling fuel or something of that nature. Did you build the plane?
I'd start looking at your ignition and electrical system. The fact that your #5 cht/egt info went "blank" for a bit sounds indicative of an electrical problem.
I would definitely heed the advice of previous posters, test the lines, clean up the fuel stain (fuel works great for cleanup of blue stains) and if you do go up and fly, see if that fuel stain returns.
I am betting my money on something other than a fuel leak
scorwin
Active Member
Thought about that as well. While we had the plug out, we did a borescope and found nothing out of the ordinary. Thought about stuck exhaust valve as well, putting pressure and fuel blowing out, just like you mentioned. Engine starts up, no "morning sickness" type events.
Flew it today and stayed around the airport. Put it through its paces: stalls, steep turns. Everything ran like it should (CHT/EGT normal), nothing out of the ordinary. Going back to the airport tomorrow, will take off the cowling again and look at everything. I have plenty of pictures to compare.
The engine did backfire on landing but I was full rich (DA prob 6000-7000ft). No other backfire episodes.
Honestly, I'm at a loss for what caused it. I've already drafted an email to Don at Airflow, to get his thoughts. Def not the end of the story here. I'm not taking anyone else up in the airplane, except for instructors/safety pilots. Staying close to the airport also, no long flights in the near future.
The plane was sitting for a long time (about a year, got painted and other things). Possibly clogged injector that has since cleared itself? Is that a possibility?
Stuck exhaust valve puts pressure in the exhaust chamber, not intake. Stuck intake valves are exceedingly rare.
A clogged injector could have done that on startup after sitting a long time, but would likely have staining near the injector. I still believe it is likely that the fuel came out at the time that the cyl dropped out. Just too much coincidence.
If you can’t find it, you can’t find it. Just don’t assume it is fixed. You seem to be taking the right steps, just keep your gaurd up.
scorwin
Active Member
I’m wondering how many of you would simply replace the fuel line, Occam’s razor kinda thing.
Without an obvious smoking gun so far, sense of false security? Or sensible plan given when happened and physical findings?
Appreciate everyone’s thoughts and time you’re putting into helping me.
Shawn
Without an obvious smoking gun so far, sense of false security? Or sensible plan given when happened and physical findings?
Appreciate everyone’s thoughts and time you’re putting into helping me.
Shawn
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while i would want a cause, if the fuel line was properly tested and passed, it is not likely the source. This assumes you trust the guy that tested it of course. Lot of really good mechanics out there, but not all of them are competent. That is a judgement call.
is this normal for your engine? I have 1500 hours on my 6 and it has NEVER backfired outside of starting events; rich, lean, or otherwise. This should be investigated imho. Backfires, excluding those that occur during starts, are exceedingly rare on a well sorted engine!
excessively rich mixtures can create afterfires however. when it gets so rich that it misfires, the next exhaust events lights the raw gas in the manifold and it explodes, creating the bang. many misinterpret this as a backfire. DA is generally irrelevant for mixture; just pressure altitude. what was that?
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scorwin
Active Member
May have been an afterfire then. No idea how to tell (if you can). I'm based at KTUS, 2600ft field elevation. Altimeter today (29.98) similar yesterday to today, so prob 2000ft. I was on short final, add a couple hundred ft to that and call it 2200ft. Full prop, full mixture. Outside air temp was ~ 102F, just to round everything out for density.
Just to add a little bit of fun to the mix and conversation. Like I mentioned, it was at DFW for 1 year for painting and other things. New W&B. Oil change. Did get a new fuel float bc the left was sticking. Had to get a condition inspection performed there, which did include re-timing the e-mags. Plugs were not changed but look good (I do have extras, can easily do that).
Plane doesn't backfire normally. No episodes on the flight from DFW-TUS a couple weeks ago.
Assuming you were at idle when this occurred? Afterfires can happen from either too rich or to lean conditions. Suggest spending some time setting your idle mixture. Backfires are well muffled so very deep in tone. Afterfires occurs in a thin metal exhaust tube. Far less deep and muffled of a tone. Backfire = light m80 in a closed, insulated cooler. Afterfire= light m80 in an empty soup can. Backfires a louder and more powerful, as they burn a lot more fuel.
Backfires outside the starting event require something seriously messed up in the engine, so not common. Afterfires can occur due to anything that causes intermittent misfiring.
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scorwin
Active Member
Went flying again today, 3rd time in the air. Could not replicate events prior times. Took cowling off, no abnormalities. Today went flying to get an idea of GAMI spread. Idea was to fly at WOT, 8500 ft, 2400 RPM. Then turn around, fly WOT, 9500ft, 2300 RPM.
Flight at 2400 RPM was uneventful. Things went well. Got peak EGT, then it started to go down. Seemed like engine was fine until FF 10.5. "Might" have been able to get lower, but looked like I got peak EGT and it was decreasing across all cylinders, so didn't push it further.
Flight at 2300 RPM felt different. Got down to 10.6 GPH on FF again and noticed the same feeling I had before. Almost like the wind was hitting the nose wheel, causing a slight abnormal feel. It was intermittent. Same what happened as first post. There was never a loss of EGT/CHT. But at 2300 RPM, seems like I should be able to go lower than where I was at 2400.
Maybe everything was ignition related, still is? I can change plugs, easy. When would you pull the e-mags and send them back to get checked?
Link below is the engine data, for those interested. I think I understand what I see, but would appreciate more experience eyes. At around 10 min- 30 min, I was at 2400 RPM. Turned around, dropped to 2300 RPM until about 50 min. Then flew back to TUS.
https://apps.savvyaviation.com/flights/shared/flight/9993108/14f16af9-3b7d-430c-832e-efebb5644e36
Flight at 2400 RPM was uneventful. Things went well. Got peak EGT, then it started to go down. Seemed like engine was fine until FF 10.5. "Might" have been able to get lower, but looked like I got peak EGT and it was decreasing across all cylinders, so didn't push it further.
Flight at 2300 RPM felt different. Got down to 10.6 GPH on FF again and noticed the same feeling I had before. Almost like the wind was hitting the nose wheel, causing a slight abnormal feel. It was intermittent. Same what happened as first post. There was never a loss of EGT/CHT. But at 2300 RPM, seems like I should be able to go lower than where I was at 2400.
Maybe everything was ignition related, still is? I can change plugs, easy. When would you pull the e-mags and send them back to get checked?
Link below is the engine data, for those interested. I think I understand what I see, but would appreciate more experience eyes. At around 10 min- 30 min, I was at 2400 RPM. Turned around, dropped to 2300 RPM until about 50 min. Then flew back to TUS.
https://apps.savvyaviation.com/flights/shared/flight/9993108/14f16af9-3b7d-430c-832e-efebb5644e36
Great to hear an update and from what I see your gremlin hasn't left the engine.
I see that you are trying to lean aggressively down to 10.6 gallons per hour.
While this is quite possible with finely tuned injectors, it is a bit much to expect the 540 to run smoothly at 10.6 GPH???
You must also consider that 10.6 GPH might not be as accurate as you think if you haven't done fuel flow verification. (Compare fuel flow data to what you see at the pump after fill up) It may be lower than indicated and thus
starve a cylinder completely and cause the scenario you describe.
I know some will chime in. and tell you they can run their 540 at 9. something LOP and do it all day long but if you haven't done the GAMI spread and tuned your injector nozzles, 10.6 is just too much (or too little fuel flow) to ask of your engine.
If I was you, I would run your engine 50 degrees rich of peak in any RPM/Manifold pressure setting and verify that it runs smoothly. You can do the LOP thing after that.
Knowing what I know now, I believe you are causing the problem by running overly lean at this point and the Gremlin may be sitting in the left seat.
(I hope you have a sense of humor)
Let us know how things turn out.
I see that you are trying to lean aggressively down to 10.6 gallons per hour.
While this is quite possible with finely tuned injectors, it is a bit much to expect the 540 to run smoothly at 10.6 GPH???
You must also consider that 10.6 GPH might not be as accurate as you think if you haven't done fuel flow verification. (Compare fuel flow data to what you see at the pump after fill up) It may be lower than indicated and thus
starve a cylinder completely and cause the scenario you describe.
I know some will chime in. and tell you they can run their 540 at 9. something LOP and do it all day long but if you haven't done the GAMI spread and tuned your injector nozzles, 10.6 is just too much (or too little fuel flow) to ask of your engine.
If I was you, I would run your engine 50 degrees rich of peak in any RPM/Manifold pressure setting and verify that it runs smoothly. You can do the LOP thing after that.
Knowing what I know now, I believe you are causing the problem by running overly lean at this point and the Gremlin may be sitting in the left seat.
(I hope you have a sense of humor)
Let us know how things turn out.
scorwin
Active Member
I asked the mechanic and he doubts this, as it starts up without any issues. I certainly dont mind asking again. This is all new to me, learning on the fly, so if I can ask, what makes you wonder about the exhaust guides?
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scorwin
Active Member
lol. yeah, that thought (Gremlin in left seat) has crossed my mind... The fuel flow point may have merit, I haven't had the plane back for long, so I dont have a lot of data, but today my red cube says I used 32.3. Took 34.9 to fill. That would make it too rich though, I think.
Question then becomes, why can't I get it to peak EGT before it stumbles?
Maybe your not giving the sensor's time to stabilize during adjustment. Or, maybe ignition problems under load.
I routinely fly at 10.5 gph at 8-10k, but i am WELL lean of peak. I agree with ernst that this is possibly too lean for stock injectors, assuming you were WOT. I would try experimenting at 20* lop. Move the knob slowly to be sure you are not missing the actual peak. If you go too fast, you will never see the actual peak and think you are not that far lop when you are.
The lower the rpm, the more load you are putting on the engine. It is not surprising that you got a bit more roughness at 2300 with the same ff as 2400, being that you were on the edge of what your setup can tolerate.
You could probably duplicate your problem by leaning until it stumbles and your #5 will go dark again before all the others if you haven't made any other changes.
If you are below 65% power you can't really hurt anything by leaning until the engine quits or at least until you see evidence of one cylinder or the other going cold.
Most likely your #5, as was the case previously. Keep some altitude above your airport for this experiment and see what happens.
You can have as much or more than a gallon of fuel difference in flow without tuning the injectors as per GAMI or Airflow Performance and that would certainly kill the flame in one of your cylinders if #5 was, say at 9.5 GPH or less.
I know the blue stain is still a source of bewilderment but as I pointed out earlier, it may be the result of a fuel spill during maintenance or something.
If you are below 65% power you can't really hurt anything by leaning until the engine quits or at least until you see evidence of one cylinder or the other going cold.
Most likely your #5, as was the case previously. Keep some altitude above your airport for this experiment and see what happens.
You can have as much or more than a gallon of fuel difference in flow without tuning the injectors as per GAMI or Airflow Performance and that would certainly kill the flame in one of your cylinders if #5 was, say at 9.5 GPH or less.
I know the blue stain is still a source of bewilderment but as I pointed out earlier, it may be the result of a fuel spill during maintenance or something.
