Houston we have a [dead cylinder].

[the_elkhartian]

AOG would love some group input.

I had been having an intermittent Alternator issue that was getting progressively worse. It almost caused a diversion on a flight back from TX on 8/15, but it quit acting up and I made it back to PHX. Life was particularly busy for a couple of weeks, but I finally flew the airplane on 9/11 just to try and replicate the issue. Alternator would go offline, but it would come right back on if I cycled the field current breaker.

8/15 Flight from TX: https://apps.savvyaviation.com/flights/4403545/a80749ad-ac57-4aac-acf6-3a0c8b2357e3

9/11 Test Flight: https://apps.savvyaviation.com/flights/4403549/734aea31-0f86-4782-a6bf-aaba91436fee

So I took it into the shop. They identified a number of improperly crimped connectors as well as several places where wire insulation had rubbed through from contact with various airframe/engine components. Theory being something was grounding out and throwing the alternator offline. So, they cleaned that up and did a couple of run tests and said it was fixed.

Test Run 9/14: https://apps.savvyaviation.com/flights/4403550/63781083-feb2-45f9-bd4a-a69c342055e9

Test Run 9/15: https://apps.savvyaviation.com/flights/4403551/976aadd9-bf0e-4400-b7b8-2ff0a4e17b5b

Pay special attention to that 9/14 test run.

I get the airplane back out of the shop and go fire it up for the first time on 9/25 and I get zero EGT reading right off the bat for Cyl. 1. I try a run-up and I'm getting a lot of vibration. 

9/25: Run-up: https://apps.savvyaviation.com/flights/4403552/c2985051-121f-43c3-92ca-5be7b7f87b6f

Shop comes and does a quick look. My first suspicion is that they have done something somehow to kill my cylinder. MIF is the best I could hope for. I get a call (this is a Friday afternoon of course) and they say that I have zero compression on my #1 and #3 cylinders. 

This week I talk to the mechanic and he says that #1 cylinder is indeed dead. Zero compression. He's able to get compression on #3 with a warm engine.

Test Run 10/1: https://apps.savvyaviation.com/flights/4403550/63781083-feb2-45f9-bd4a-a69c342055e9

A friend of mine was able to go by yesterday and download the JPI Datat (I have the cable! But I don't have the downloader box...and I've been a CB holding out to use that money for a more modern engine monitor...) And here we are today.

I appreciate your insights and theories, all of ye sage engine monitor geeks and wizards.

 

JP

[carusoam]

It’s been a while since anyone posted a good JPI puzzle!

Any idea on how many hours are on those cylinders/rings..?

Best regards,

-a-

[David Lloyd]

Morning sickness.  Sticking valve.  Do you want your MX to troubleshoot, possibly pull the cylinder or do your own investigation?

[the_elkhartian]

7 minutes ago, carusoam said:

It’s been a while since anyone posted a good JPI puzzle!

Any idea on how many hours are on those cylinders/rings..?

Best regards,

-a-

I'll have to go back and look at the logs....from memory I think that 1 & 3 might go all the way back to the last overhaul--1995 and about 1500 hours. #4 cylinder was replaced more recently.

5 minutes ago, David Lloyd said:

Morning sickness.  Sticking valve.  Do you want your MX to troubleshoot, possibly pull the cylinder or do your own investigation?

Would definitely prefer to investigate and resolve myself! What steps should I take?

[carusoam]

1) Cylinder one appears to not be firing very completely... it is warming up... 

But, if you have no compression what else are you going to do but get the compression back..?

2) If you look to prior flights... you will probably see High EGTs caused by this in flight... raw fuel making it to the exhaust pipe and burning once it is there...

3) If you look at the peaks of the of the run up... they should be identical... assuming you do a finely controlled run-up...

4) There is some timing difference indicated by the run ups... one peak is taller than the other...

5) Delayed timing dumps raw fuel into the exhaust registering a higher EGT...

6) Read up on the best ways to collect run-up data... 

7) When you do it too quickly... the three or four data points you collect aren’t as meaningful as 10 or 12...

8) Which JPI do you have? Why do you need the box?

9) lesser JPIs dump data to cheap laptops that can be found for near zero from graduating high schoolers... (source of my plane’s JPI laptop)

It would be great if you can collect some additional data... an inflight mag test has a great advantage...

Tell us some detail about your run-up... how long did you hold the key in each position..?  What did you use to know when click to the next position..?
 

Best regards,

-a-

[carusoam]

wait a minute....

Might you want to expand on why a cylinder has left this fine engine previously to begin with?
 

Might it have something in common with its brothers?
 

Next steps followed by MSers lately...

Any concerns about compression...

1) Follow the rules for compression testing very closely... make sure the proper orifice is being used... proper heating of the engine... the whole nine yards...

2) Get pics of the valves to see how they are behaving... while you are in there... pics of the cylinder walls are going to be very telling.... get pics of the diamond pattern that is etched in the cylinders to improve compression... if you don’t have compression... it’s possible you no longer have any diamonds...

3) Sticky and misbehaving valves leave messy fingerprints all over the place.... They can’t clean themselves up after the crime is committed... 

4) You can get up to speed with all of this by reading at the Savvy website...

5) Sticky valves are a lack of rotation... 

6) Stuck valves are not moving at all...

7) Stuck valves have a tendency to collide into the piston...

8) Losing power during T/O is an uneasy feeling... (my one stuck valve experience, without an engine monitor...)

PP thoughts only, not a savvy mechanic...

Best regards,

-a-

[the_elkhartian]

1 hour ago, carusoam said:

2) If you look to prior flights... you will probably see High EGTs caused by this in flight... raw fuel making it to the exhaust pipe and burning once it is there...

When I look at prior flights or longer flights, I see #1 showing a consistently lower EGT...

1 hour ago, carusoam said:

But, if you have no compression what else are you going to do but get the compression back..?

Would a failed ring in #1 explain the compression? The current plan is to scope the cylinder and see if the valves are opening/closing properly. If so, that would narrow it down to a piston issue....or the diamond etching you mentioned.

1 hour ago, carusoam said:

8) Which JPI do you have? Why do you need the box?

I have a 700....I guess I haven't thought about buying an old used laptop to run the JPI software. I am a Mac user at home and my work PC is so locked down with defense-level security that you can't even plug in a mouse. It's a simpler more elegant solution just to buy the $170 JPI box... but I might look around for an old PC with a serial port for a little while.

1 hour ago, carusoam said:

Tell us some detail about your run-up... how long did you hold the key in each position..?  What did you use to know when click to the next position..?

So I've never really thought about it. Mag check process I follow is run up to 2000 rpm, normalize the readout on the JPI, switch to single mag watch EGT +/- equally peak on all 4 cyls, then back to both and watch it come back down, then to the other mag same process. You bring up an interesting point that if I'm not doing that for at least 6 seconds then I'm not getting any good data recorded. I'll start singing the "happy birthday" song on each mag going forward. This is also why I would like an updated JPI monitor.

1 hour ago, carusoam said:

wait a minute....

Might you want to expand on why a cylinder has left this fine engine previously to begin with?
 

Might it have something in common with its brothers?

More/better info. All 4 cyls. overhauled 3/31/00 or about 1100 hours ago.

Looks like #4 failed 8 years/500 hours later and was replaced.

[David Lloyd]

During the compression check, was the exhaust or intake valve leaking?  Air sound at exhaust, exhaust valve.  Air sound at oil fill, intake valve.  Really, since it is a certified aircraft, just get with the mechanic. Pull the valve cover, move the prop (be safe, remove the spark plugs) and chances are you will observe the valve being stuck open.  The two sticking valves I dealt with, one required a little hammer work to remove the valve from the guide.  The other needed a hammer, a brass rod and some serious swings to coax the valve to move. I couldn't believe the pushrod wasn't bent.  A properly operating valve glides  easily in the guide, almost frictionless.  The valve is removed from the guide and the valve guide reamed to the proper size and reassembled.  Okay, once you establish a stuck valve, will the mechanic remove the cylinder for repair himself or send to a cylinder shop?  Or do the Lycoming approved rope trick? That involves repair with the cylinder in place, dropping the valve into the cylinder, reaming the guide, getting the valve stem back in the guide  (a trick in itself), holding the valve in place with a piece of rope stuffed in the cylinder while getting the valve spring and keepers back in place.  A lot of mechanics just shake their heads.  Search VansAirforce for a blow-by-blow on how to do it. Quite entertaining, but once you know it is a stuck valve, a fair amount of surgery is required.  

[carusoam]

To get compression...

The rings have to be working...

Rings do break... 

Oil analysis may show their failures...

If you know what coating if any were in the cylinders, that can give a hint to...

From the logs... it looks like, low compression one day, cylinder OH was done...

A good pic of the cylinder wall will tell a lot more than the brief note in the log...

See how many hours are on the cylinders in its life?

Any oil use age to go with that?

Best regards,

-a-

[Guest]

1 hour ago, wingtipwalker said:

AOG would love some group input.

I had been having an intermittent Alternator issue that was getting progressively worse. It almost caused a diversion on a flight back from TX on 8/15, but it quit acting up and I made it back to PHX. Life was particularly busy for a couple of weeks, but I finally flew the airplane on 9/11 just to try and replicate the issue. Alternator would go offline, but it would come right back on if I cycled the field current breaker.

8/15 Flight from TX: https://apps.savvyaviation.com/flights/4403545/a80749ad-ac57-4aac-acf6-3a0c8b2357e3

9/11 Test Flight: https://apps.savvyaviation.com/flights/4403549/734aea31-0f86-4782-a6bf-aaba91436fee

So I took it into the shop. They identified a number of improperly crimped connectors as well as several places where wire insulation had rubbed through from contact with various airframe/engine components. Theory being something was grounding out and throwing the alternator offline. So, they cleaned that up and did a couple of run tests and said it was fixed.

Test Run 9/14: https://apps.savvyaviation.com/flights/4403550/63781083-feb2-45f9-bd4a-a69c342055e9

Test Run 9/15: https://apps.savvyaviation.com/flights/4403551/976aadd9-bf0e-4400-b7b8-2ff0a4e17b5b

Pay special attention to that 9/14 test run.

I get the airplane back out of the shop and go fire it up for the first time on 9/25 and I get zero EGT reading right off the bat for Cyl. 1. I try a run-up and I'm getting a lot of vibration. 

9/25: Run-up: https://apps.savvyaviation.com/flights/4403552/c2985051-121f-43c3-92ca-5be7b7f87b6f

Shop comes and does a quick look. My first suspicion is that they have done something somehow to kill my cylinder. MIF is the best I could hope for. I get a call (this is a Friday afternoon of course) and they say that I have zero compression on my #1 and #3 cylinders. 

This week I talk to the mechanic and he says that #1 cylinder is indeed dead. Zero compression. He's able to get compression on #3 with a warm engine.

Test Run 10/1: https://apps.savvyaviation.com/flights/4403550/63781083-feb2-45f9-bd4a-a69c342055e9

A friend of mine was able to go by yesterday and download the JPI Datat (I have the cable! But I don't have the downloader box...and I've been a CB holding out to use that money for a more modern engine monitor...) And here we are today.

I appreciate your insights and theories, all of ye sage engine monitor geeks and wizards.

 

JP

Sure sounds like sticking valve.  The mechanic who did the compression check should be able to tell you where the air was going during the compression check, exhaust or intake leak from the valve or leaking past the rings and out the breather.  The fact that he got compression on #3 after it warmed up suggest a stuck valve.

Clarence

[markgrue]

If you are so inclined take at lot at Lycoming service instruction 1425A.  It is in the downloads section under "Lycoming sb for reducing the occurance of stuck valves"  It will detail the procedure for cleaning exhaust valve guides.  It is recommended to do this every 400 hours.

Mark

[the_elkhartian]

Scoped the cylinder this morning and found that the Valve seat had come loose and moved to keep the valve in a stuck open position. 

Pulled the cylinder and this is what he found (in addition to improperly torqued bolts holding the cylinder on)...

The intake valve is stuck open with the valve seat wedges underneath it. 
 

It was sticking up enough that it actually came in contact with the piston. 

The question according to my mechanic is if the valve seat can be re-seated or if it requires replacement. He’s also going to soak the piston to see if there’s any major damage from that impact but he doesn’t think so. 
 

Any other thoughts or comments from the group?

[kmyfm20s]

I would replace the piston. Who knows what fracture have been initiated or are undetectable as a result of the valve hitting on it. I would hate for it to come apart after putting things back together latter down the road. Funny the photo of the top cylinder looks like a hole next to the spark plug but I’m sure it’s just an illusion from oil or a shiny spot. 

Edited October 5, 2020 by kmyfm20s

[carusoam]

Check the history of that thing...

That way you feel better about tossing it out...  

what is the other dark odd shape mark along with the plug holes and valves?

Great pics, WTW!  That was quick...

Best regards,

-a-

[carusoam]

We don’t usually get such a good view inside the cylinder...

There are three things that look odd to me....

Besides the valve seat escaping...

1) molten metal look... left arrow.

2) Fibrous material look... top arrow

3) broken metal look... right arrow

What is causing these image anomalies...(?)

Is that a hole to the outside?

PP thoughts only, not a mechanic at all...

Best regards,

-a-

 

 

[kmyfm20s]

I mentioned that also. I think it’s a little pool of oil but sure looks like a hole from the photo!

[carusoam]

Since you can see the cylinder wall while it is out...

Does it have any cross hatch pattern left on it?

Usually, it takes good focus to capture it with the camera...

If the walls have shiny smooth spots, their oil distribution will be affected...

Best regards,

-a-

[the_elkhartian]

54 minutes ago, carusoam said:

what is the other dark odd shape mark along with the plug holes and valves?

It’s just really shiny oil. That area of the cylinder looks just like the other non-shiny-black-hole-to-another-dimension part of the cylinder you see above/below/right of that spot. 

 

35 minutes ago, carusoam said:

Since you can see the cylinder wall while it is out...

Does it have any cross hatch pattern left on it?

It’s pretty smooth. I specifically looked but did not observe any cross hatching on the cylinder walls. 

[carusoam]

8 minutes ago, wingtipwalker said:

It’s just really shiny oil. That area of the cylinder looks just like the other non-shiny-black-hole-to-another-dimension part of the cylinder you see above/below/right of that spot. 

 

It’s pretty smooth. I specifically looked but did not observe any cross hatching on the cylinder walls. 

That may be the logic needed to search for an OH of the cylinder... ask your mechanic in case it’s there and you didn’t recognize it(?)

Best regards,

 -a-

[jaylw314]

On 10/3/2020 at 3:03 PM, wingtipwalker said:

I have a 700....I guess I haven't thought about buying an old used laptop to run the JPI software. I am a Mac user at home and my work PC is so locked down with defense-level security that you can't even plug in a mouse. It's a simpler more elegant solution just to buy the $170 JPI box... but I might look around for an old PC with a serial port for a little while.

Complete sidebar, but you can use any Windows laptop with a USB-to-serial adapter, they cost $20 or so.  I posted the Amazon link (not all adapters are known to work) for the one I used a few years ago, someone can do the Google-fu if needed...

[DXB]

14 hours ago, wingtipwalker said:

my mechanic is if the valve seat can be re-seated or if it requires replacement. He’s also going to soak the piston to see if there’s any major damage from that impact but he doesn’t think so. 

Maybe I'm over-reacting, but it seems like the forces involved in a piston striking the intake valve after the seat shifts wouldn't leave me with much faith in the integrity of that cylinder head even if it looks ok visually after sandblasting and inspecting carefully for cracks. It would make me want to go with all new hardware rather than try to recondition that jug and put in a new seat and valve.  

[Greg Ellis]

13 hours ago, carusoam said:

 

What is causing these image anomalies...(?)

Is that a hole to the outside?

PP thoughts only, not a mechanic at all...

Best regards,

-a-

 

 

I looked at that as well and thought surely it has to be something other than a hole to the outside.  If my mechanic only worried about a stuck valve and talked about trying to fix the stuck valve, with a hole this large to the outside then I would be looking for a new mechanic. 

[carusoam]

only somewhat Related to the OP’s challenge...
 

When my O360 stuck a valve...

The piston crashed the valve until it freed up...

The dent in the piston was relatively small...

But, the bend in the valve’s rod was pretty big...

It got a new to me OH’d cylinder, but the piston stayed in place... IIrC 

Crummiest pilot thinking to date... run-up was fine, because the valve. Was hammered free... flew it home a half hour away... then had the mechanic look at it...  
 

Had a CFI on board as well... we both should have known better options...and considered them strongly...  No engine monitor to say Hey look at me!
 

Airplanes don’t fix themselves...

 

PP thoughts only, not a mechanic...

Best regards,

-a-

[Bartman]

Ok so here’s another thing to consider. With a stuck or partially stuck valve the lifter is no longer in constant contact with the camshaft lobe. What kind of damage can that cause ? Would it look something like this ?

[the_elkhartian]

1 hour ago, Bartman said:

Would it look something like this ?

The lifter “collapsed”...To be totally honest I’m not comfortable with the mechanics of what that means. But (I’m told) there was not the tell-tale metal on metal tapping sound I’m told is a bad sound when you’re dealing with unhealthy lifter-to-cam lobe impact. 

Mechanic said he would inspect the cam to make sure there wasn’t any damage.