FlyTy

Had a Partial Power Loss Experience

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Hi everyone, just wanted to share an experience I had yesterday while on an IFR training flight. We departed out of Petaluma and we were flying to Livermore. The flight went well until touchdown at Livermore, then the engine died on me. I had enough speed to be able to make a taxiway and got off the runway, but I was stuck on the taxiway. So I switched tanks and we were able to restart the engine using the flooded technique, but it was running really rough. The instructor and I thought maybe it was fouled plugs, so we hobbled over to the run-up area and ran the engine at a high RPM and leaned the mixture. We did this a couple times and seemed like the engine was running normally again.

We took off out of Livermore and climbed to our altitude while circling near the airport out of precaution. When I reduced power to start my descent into Petaluma, the engine started to run really rough again, to the point to where it felt like it was about to die on us. We were able to maintain 2000' until we were close enough to make the airport in case of a complete engine failure. The instructor was periodically adding power to keep the engine going, otherwise it felt like it was going to quit, while I was flying it down. We made the runway, and once on the ground it sputtered even more, but if we advanced the throttle it would kick back to life for a few moments. We were able to make it back to my hangar, then when I tried to shut down the engine, it wouldn't shut down. The throttle and mixture were both back all the way and it was just sputtering. It finally stopped when I turned the mags to "off".

Getting out of the plane I noticed the front tire covered in fuel. A little later I took off the cowling to look for anything obvious. I noticed exhausted deposits on the bottom of the top cowling, then saw what looks like exhaust deposits on the spark plug wire on cylinder #3, picture attached. It seemed like the engine was happy at higher RPMs, and only started to get rough at a lower RPM. During descent, adjusting the mixture didn’t seem to help, carb heat was on, fuel pump was on, switching tanks did nothing. We checked the mags on the ground in Livermore and they were within limits. I wish we checked them in the air just to say that we tried, but the instructor is pretty sure it’s not a mag issue. I also checked the fuel sumps and gascolator sump and it was all clean 100LL. Oil level didn’t show any abnormal loss.

I did some searching on here and noticed some others that had similar issues, I don’t recall them posting what solved the issue, but it seemed like they were induction or ignition issues. My instructor thinks the problem is coming from the carb. I’m worried #3 cylinder is cracked, but would a cracked cylinder have these symptoms? The shop in Petaluma said they could take a look at it this coming week and I’ll update this thread when I find out more, but any ideas from the community are welcome! But really just wanted to share my first true nerve-shaking experience.

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Congrats for getting on the ground safely...

Fuel leaking out should be a very obvious thing to find the source...
 

There is no normal for fuel leaks...

check the fuel line to the carb...

The carb is where fuel goes from all liquid to mostly vapor...

Blue staining will be a significant sign...

There is a drain for the carb... if you were to over prime.  Fuel drains down onto the tire...
 

Fuel pumps have a drain on them as well... broken diaphragms may cause some extreme leaking while appearing to work normally...

Problems at low power typically are a hint that there may be a leak in the air intake....   drawing extra air in... no fuel leak this way...

Got any engine monitor data?

What makes you think a cylinder may be cracked?

See if you can take some better pics with the cowl off...

Verify these three fuel drains aren’t dripping fuel... two pumps, one carb... 

Unexplained fuel leaks under the cowl is a do not fly kind of thing.... hot surfaces and gasoline are bad...
 

if a leak is happening after the electric fuel pump... you may get fuel leaking while it is on... and air leaking in while it is off...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

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The leaking wasn't continuous, just noticed a lot of fuel when I went to push my plane in. It has been dry since. 

Unfortunately I do not have an engine monitor, just, what looks likes, a single probe EGT/CHT gauge. 

If not a cracked cylinder, what else could cause an exhaust mark like that? 

And I have a few more pictures that I look immediately afterwards and showed the A&P... he didn't even raise an eyebrow to them, although, in my opinion, it doesn't look good. I also noticed the air intake ducting wasn't secured. But it looks to me like the gasket for the carb has a leak? Also the oil on the muffler is disconcerting.

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I had similar symptoms from a stuck float.  This will cause an excessivly rich mixture at low power settings.  Engine would not idle, rough when advancing throtle, hard to shut down, ran fine at full power.  Fuel dripped from the carb when the fuel pump was on.  I pulled the air filter to watch for fuel in the airbox, but it leaked out the bottom after a few seconds anyway.  

I resolved the issue by draining the carburetor a bunch of times (drain, refill with fuel pump, drain again).  I used a catch can to catch the fuel and confirm there was no sediment. 

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Carburetor would be my first pick, I’m no expert, but some carburetors have an idle jet that could be clogged or as mentioned a stuck float. I would get come carburetor cleaner and give it a good cleaning and go from there. Start with the inexpensive and easy fixes first.

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Sounds like a carb issue.  We had increasing problems going from idle to full throttle, sputtering at low power (approach), and starting.  We pulled and and sent to be OH.  They called and said they were donating it to a museum, it was unservicable and in bad shape.

 

Plane has run great ever since then ;-)  

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Have you figured out the cause of the staining above cylinder #3?

Clarence

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@M20Doc No... I will be going by the hangar in a bit to try and get some better pictures. 

Thanks everyone for your input! 

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4 hours ago, FlyTy said:

@M20Doc No... I will be going by the hangar in a bit to try and get some better pictures. 

Thanks everyone for your input! 

In the pictures you posted, you appear to be missing the heat shield and Adel clamps for your oil cooler transfer hoses at the left cowl flap.  There was a thread just the other day on the very subject.

Look for the thread Found my oil leak

Clarence

Edited by M20Doc
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Is there some fuel staining at the carb/bowl split line?  Precision published a couple service bulletins that may affect your carb.  One is for bowl leaking/security and the other for replacement of the float.  Copy the links into your browser... 

http://www.msacarbs.com/pdf/MSA-13.pdf

https://msacarbs.com/pdf/MSA-14.pdf

MSA-3 says 10 years between carb overhauls, if I remember correctly...

tom

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@M20Doc It seems like a usual thing for these planes to not have that heat shield? My hangar neighbor with an F didn't have them when I checked out his engine today. Anyways, definitely worth looking into, thanks! Also, I was happily wrong about the cylinder crack idea. I guess because the way our air flows through the engine compartment, exhaust deposits can find their way up through the cooling fins and on the spark plug wires on the #3 cylinder. The hangar neighbor has the same thing happen. I took a picture anyways. 

@47U Thanks for those! Yes, It looks like there is fuel staining. Also noticed when I turned the fuel pump on, I have a leak out of the fuel pressure sender line. Picture attached where it is leaking. I think you can also see the staining? 

 

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4 hours ago, FlyTy said:

@M20Doc It seems like a usual thing for these planes to not have that heat shield? My hangar neighbor with an F didn't have them when I checked out his engine today. Anyways, definitely worth looking into, thanks! Also, I was happily wrong about the cylinder crack idea. I guess because the way our air flows through the engine compartment, exhaust deposits can find their way up through the cooling fins and on the spark plug wires on the #3 cylinder. The hangar neighbor has the same thing happen. I took a picture anyways. 

@47U Thanks for those! Yes, It looks like there is fuel staining. Also noticed when I turned the fuel pump on, I have a leak out of the fuel pressure sender line. Picture attached where it is leaking. I think you can also see the staining? 

 

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To me it’s odd to see exhaust soot above the cylinder.  If you’ve got a compression tester I would use it to do a compression test, then while the cylinder is under pressure spray the cylinder head between the fins to look for a crack indicated by bubbles.  Head cracking is more common on TCM engines than on Lycoming, but is worth confirming.

I may be wrong but the second picture here the fuel pressure hose appears to be the wrong type, normally used in low pressure instrument air and will become stiff and brittle with oil and fuel.

If you’ve got a shop vacuum cleaner available connect the outlet side to the tailpipe with some duct tape and pressurize the exhaust, again spray the system to find leaks and cracks.

Clarence

Edited by M20Doc
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When in BUMPY IMC yesterday, there was someone on the radio with partial power loss. I tried to squeeze in a silent prayer for them while I was focused on keeping the shiny side up.  They made it down okay.

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@47U Got to thank you again for those. I went by the hangar and checked out the carb. Loose bolts, leaking gasket, no stamp on the plate to indicate the new float. I went to the shop with this information and they agreed it was the issue. New one on order, should be here Wednesday and hopefully back in the air by the end of the week. 

@M20Doc They will be replacing that line with a new and correct one when they install the new carb.  

I agree it is odd. The plane will be in for annual at the end of July and I'll make sure to have them take a look at it. In the mean time I like your idea of pressurizing the exhaust. 

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Where is it going for annual..?

The things you listed are often a side affect of... (doesn’t really matter about the history, it’s where you are going that is important...)

Pick a resource that really knows Mooneys...

Many Mooneys we’re not born with things that really make sense to have... heat shields, and silicone hose protectors...  seat belts... no smoking signs... carb ice systems that actually work...
 

this is in the update your Mooney to modern safety specs kind of thing...

Most Mooneys far exceed time recommendations for OH on devices like a carburetor... On condition is meaningful... somebody In the know has to look...   

Tell us about your CO monitor... often exhaust getting out before the exhaust pipe, gets noticed by the subtle beeping of the CO alarm...
 

Which one do you have?

Best regards,

-a-

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2 hours ago, carusoam said:

Where is it going for annual..?

The things you listed are often a side affect of... (doesn’t really matter about the history, it’s where you are going that is important...)

Pick a resource that really knows Mooneys...

Many Mooneys we’re not born with things that really make sense to have... heat shields, and silicone hose protectors...  seat belts... no smoking signs... carb ice systems that actually work...
 

this is in the update your Mooney to modern safety specs kind of thing...

Most Mooneys far exceed time recommendations for OH on devices like a carburetor... On condition is meaningful... somebody In the know has to look...   

Tell us about your CO monitor... often exhaust getting out before the exhaust pipe, gets noticed by the subtle beeping of the CO alarm...
 

Which one do you have?

Best regards,

-a-

I'm taking it to the shop on the field, Mangon Aircraft. One of their A&P's used to work at LASAR. He seems to know his way around a Mooney and he also did the flap spar SB on mine. That being said, I am a 30 minute flight to LASAR and to Top Gun. However, I've been hearing mixed reviews about the local MSC's from a couple local owners. I also hear mixed reviews about the shop on the field, but they did well last year except that someone forgot to tighten a nut on the left cowl flap, which caused some really loud vibrations during run-up. So, damned if I do, damned if I don't. 

I use a Sentry ADSB receiver that has a CO detector. They also tested the exhaust for leaks last year and didn't find any... hopefully the receiver will detect the CO if any leaks have sprung up. 

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