Engine problem - suggestions + support needed

Hey Guys. Here's the story - bear with me !!

Technical info: O-360 A1A 180HP // +/- 80hrs since full overhaul at Lycoming - Yellow tag engine.

Hangar and Ext. Temp -9 deg C (15 deg F)

Went to the hangar today, took off the cowlings and changed the oil + filter for winter (Exon Elite 20W-50). While I was doing misc maintenance on the plane, I pluged the pre-heater pad + my heater for an hour, everything covered under my engine cover laying over the engine bay.

Then I started the engine which started on the first 1/4 turn - All good.

I left the engine idling @ +/- 850RPM for a couple minutes, gradualy leaning... Then 1000rpm fully leaned idle for at least 5 minutes till I started to see the oil temp needle rising. Then I gradualy put full mixture and raised the engine to 1700rpm and did a quick mag check - all good. I left the engine run at 1700rpm for a couple minutes, during which it got up to +/- 75deg. F. on the oil temp gauge. (note that both cowlings were not on the engine while I did the test run so, the engine is much harder to warm up)

Once I had +/- 75 deg. F, I increased the RPMs to 2000, to get the engine somewhat up to normal temperature. Left the engine run at 2000rpm for 2-3 minutes, then back down to 1000RPM lean idle and left it there for a minute. Highest temperature I got on the gauge was aprox 90 deg. F. (again, no cowlings...) All other parameter in Green.

Here's the interesting part. I put full rich, then increased the throttle to get 2000RPM again and the engine hesitated and burped, as if it was missfiring. As I increased the throttle slighly, the engine dropped in RPM as if a "choke" was on and it backfired - then I pulled the throttle to idle and leaved it alone for a second while I gradualy leaned it.

Engine still turned fine on idle. After 30 seconds, full mixture and I increased the throtle to get to 1700RPM to do another mag check, it hesitated a bit but eventualy got up to 1700RPM and stayed there while I checked both mags to make sure. All Good. Once done, I increased the throttle to obtain 2000RPM, again - same thing, hesitation then drop in RPM. I cut the thottle before a backfire could occur this time...

I stopped the engine, did a visual check and inspected for leaks, checked the oil. All good.

Got back in, did pretty much the exact same thing. It hesitated a little bit between 1000 and 1500RPM, but I increased the throttle verry gradualy, I ran it full power and it didn't hesitated this time at higher RPM...

I brought the RPM to 1000RPM, full lean for a minute then pull the mixture off. Than I ran to my computer to write this message!! Joking of course, I had dinner before running to my PC actualy....

Now, what do you guys think might cause this?

While doing test run, I often switched tanks, to try to eliminate variables one by one. I ran with the boost pump on, didn't changed anything. There was no water in the tanks. The tanks vents under the fuselage seam to be free of any debris and I ran a cable into them whitout any obstacles.

One other thing. The very last flight I did was back in mid September. After about an hour of flight, I lined up on the runway in a nearby town for the last leg back home, gave it full throttle, then the engine hesitated and did the exact same symptoms it just did today. It wouldn't take full power. BUT, I had just washed the plane a couple minutes ago and I thought at this point that water must've had acumulated in the carburator housing/bowl or in the air filter, and got sucked in on full power. That day, I cleared the runway and got back to the parking area to check anything I could. After 10-15 minutes laying there with the engine stopped, I tought to myself that the heat coming from the engine would make any remaining water evaporate and dry... After I restarted the engine, it ran fine and got back home safely and without any hesitation from the engine.

A couple things I suspect.

-carburator problem
-missfirering / spark plugs
-fuel filter / fuel system

Let's hear what you guys think!

I would try running it up with the mixture pulled out 1/2 inch to an inch, sounds like to me it is running to rich with the mixture all the way in. Maybe I'm over simplifying it we will see what others say.

idle mixture

Check the idle mixture, sounds a little lean (would make sense in winter...colder, denser air). Sometimes seasonal tweaking is necessary if temps swing considerably in your local.

Symptoms sound like possible carb ice, but you said it is -9C. outside, so I am wondering if there is even enough moisture in the air to cause carb ice??

DAGO said:

Did you check your sumps for water??? How is the condition of your fuel caps seals?

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Oil Sumps or Fuel sumps? Please clarify. English is a second language for me and sometimes, those terms don't mean the same thing when we use it in a french conversation... Fuel caps have 80hrs, as the plane, they're brand new, but I haven't checked... should I ?

Mike S said:

Symptoms sound like possible carb ice, but you said it is -9C. outside, so I am wondering if there is even enough moisture in the air to cause carb ice??

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-9 outside and inside - low humidity. Also, the engine did the same thing on takeoff in Sept on a 20deg C sunny day.

Your issue is normal, when the Carb is transitioning from
Idle mixture to main meter there is a period when the mixture
Is lean, this happens quickly. The correction is to not jab the throttle, but to smoothly add
It.

Check throttle shaft for slop. Quick/easy.

What's the part # on your carb?

tadsargent said:

Your issue is normal, when the Carb is transitioning from
Idle mixture to main meter there is a period when the mixture
Is lean, this happens quickly. The correction is to not jab the throttle, but to smoothly add
It.

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ihh... don't know about that. When I increase the throttle, I always do it gradualy. That's the way I learned to do it, and keep doing it.

Also, when I go from 1000 RPM to 1500rpm - the mixture has been put to rich 5-10 seconds before. I might agree... But when I go from 1500RPM to 2000RPM, the engine has been running full rich for a while, and still hesitate.

lockeed said:

Oil Sumps or Fuel sumps? Please clarify. ...

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The "Oil sump" is also known as the "Oil pan" in cars. It is the bottom of the engine where the oil collects.

The "Fuel sump" is can also be called the gascolator, as used in carbureted engines. It can also be any low spot in the fuel system that has a quick drain on it, such as on our wings.

Mike S said:

Symptoms sound like possible carb ice, but you said it is -9C. outside, so I am wondering if there is even enough moisture in the air to cause carb ice??

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Considering how new the engine is and that it was apparently operating fine the last time you flew it, I'm with Mike.... Carb. Ice.

Now that you have ground run and leak checked it, I suggest you put the cowl back on and try it again.

I drainned the tanks from the drain under both wings. But I haven't drained the gascolator - didn't tought about it. I have experience with car mechanic, but items like the gascolator are new to me.

See picture to make sure we're talking about the same thing.

aerhed said:

Check throttle shaft for slop. Quick/easy.

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Are you talking about the push/pull cable?

With carburetor operations, it is not unusual for the engine to stumble in the range of 1200-1500 RPM. What is happening is that the idle circuit is closing off and the venturi is picking up. In that transition range is where the stumble occurs.

The stumble may not be related to other things going on in the engine. Also, if you get hesitation from 1500-2000 RPM, it is probably not due to the transition.

You could have carburetor icing, water in the fuel, a leaking primer line, bad magneto timing, etc.

Because you had something similar in September, if it were me, I might start by putting the plane into a warm hangar to melt any ice that formed in the fuel tanks. Then, I would drain avgas to be sure there was no water in the fuel, and be sure the magneto timing was correct. The thought being to get ideal fuel supply and ignition to see what happens then.

Check PM

Dan

rocketbob said:

What's the part # on your carb?

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Carburator: Marvel/Schebler
Part # 10-3878
model: MA-4-5
Serial: G 51 9231

Overhauled at the same time as the engine.

Running Engines without cooling system attached

(note that both cowlings were not on the engine while I did the test run so, the engine is much harder to warm up)


--cylinder barrel overheating and piston scuffing concern--

At high power settings without cowling the cylinder barrels are not adequately cooled. In a demonstration test-cell test we did years ago on a O-320 the engine ran fine at idle and up to mid power range for a short duration test run.

When attempting to go to full power smoke was seen coming from the cylinder barrel paint within 1 minute. When we removed the cylinder we had severe piston scuffing.

CHT and oil temperature had not responded and in fact may have never gotten above red-line as they do not measure cylinder barrel temperatures.

Test was done at about 70 degrees ambient. Although I have no cold weather experience (California guy), I would be careful about cold temperatures due to the large temperature differences.

At one time Ram Aircraft was selling (or attempting to sell) a portable engine shroud for running engines on the airplane with the upper cowling removed. Would make a nice group project.

The arrows in the picture you sent are pointing at the gascolator. You should check for water in the gascolator every time you fly along with your fuel tank sumps. Do this after every refueling, also.

Possible intake hose leak. These are the hoses that connect the carb area to the cylinder intake area. They will cause a very lean transition and very rough spot along with the burps you diescibe.
Dave62 (Swift Driver)

Not push-pull cable. Throttle shaft in carburetor. Throttle plate (butterfly) is attached to throttle shaft about an inch & a half below the oil sump (pan?). When shaft & bushings are worn they suck air and can exhibit the symptoms you describe. Your engine is low-time Lyc rebuilt, but you didn't specify carburetor time. Open throttle 2/3-3/4 travel. Grab throttle arm (what cable attaches to) and wiggle. Do the same on other end of shaft. Noticeable play means air suckage. Takes only seconds to eliminate this as a possibility.

john.schwaner said:

(note that both cowlings were not on the engine while I did the test run so, the engine is much harder to warm up)


--cylinder barrel overheating and piston scuffing concern--

At high power settings without cowling the cylinder barrels are not adequately cooled. In a demonstration test-cell test we did years ago on a O-320 the engine ran fine at idle and up to mid power range for a short duration test run.

When attempting to go to full power smoke was seen coming from the cylinder barrel paint within 1 minute. When we removed the cylinder we had severe piston scuffing.

CHT and oil temperature had not responded and in fact may have never gotten above red-line as they do not measure cylinder barrel temperatures.

Test was done at about 70 degrees ambient. Although I have no cold weather experience (California guy), I would be careful about cold temperatures due to the large temperature differences.

At one time Ram Aircraft was selling (or attempting to sell) a portable engine shroud for running engines on the airplane with the upper cowling removed. Would make a nice group project.

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Good point John, and I totally agree, high/full power engine runs on the ground should be kept as short as practical and used only to verify proper engine operation. Maybe 10-15 secs max with cool down between runs.

LONG SHOT

I was coming in to the pattern with my trusty MA4-5 and I had a short engine roughness followed by the engine choking and losing power with any power application. The engine ran fine as long as I didn't add power. I had a pretty good idea what had happened before I landed, because the exact thing happened to my VW Bug 30+ years previous.

1) Engine roughness was caused by the brass accelerator pump fuel nozzel passing through the valves.

2)Power application choking was caused by fuel gushing out of accelerator pump nozzel hole with power applications.

Steve Barnes "The Builders Coach"

aerhed said:

Not push-pull cable. Throttle shaft in carburetor. Throttle plate (butterfly) is attached to throttle shaft about an inch & a half below the oil sump (pan?). When shaft & bushings are worn they suck air and can exhibit the symptoms you describe. Your engine is low-time Lyc rebuilt, but you didn't specify carburetor time. Open throttle 2/3-3/4 travel. Grab throttle arm (what cable attaches to) and wiggle. Do the same on other end of shaft. Noticeable play means air suckage. Takes only seconds to eliminate this as a possibility.

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Carb was ovehauled at the same time as the engine.

Steve Barnes said:

...fuel nozzel passing through the valves.

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Can you elaborate? Do you mean that a nozzel would've come loose and would've traveled up in the engine?

lockeed said:

Carburator: Marvel/Schebler
Part # 10-3878
model: MA-4-5
Serial: G 51 9231

Overhauled at the same time as the engine.

Click to expand...

You've got the wrong carb. 10-41641 is the one you want and will have the main jet sized properly to avoid the stumble. You can change the jet to match the 41641, thus the part number will change.

rocketbob said:

You've got the wrong carb. 10-41641 is the one you want and will have the main jet sized properly to avoid the stumble. You can change the jet to match the 41641, thus the part number will change.

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What?

The engine has been overhauled at the lycoming factory (yellow tag) and the carburator has been overhauled at Consolidated Fuel Systems Inc down in Alabama.

Do you mean that just changing the main jet, it would solve the issue. DO you also mean that the carburator 10-41641 is the same as mine ,execpt for the main jet ?

Again ,I need details before I play with the carburator, which always ran perfectly before, and still is on some occasions.

Yep. The carb part number used is airframe-specific. 10-41641 works the best for the RV with the O-360.

The only difference is the size of the main jet and the economizer jet setting. I can't remember if the discharge nozzle is different.

You will get rid of the stumble setting the carb up for the 10-4164 specs.

10-3878 is the most efficient and basic carb, the 10-4164 runs a little richer. There is also a 10-3878M part number that is slightly richer, not sure if that solves the stumble problem.

I had this same problem with an overhaul from the same place. I returned the carb under the lycoming warranty and that fixed the issue. In all likelyhood the accelerator pump is the issue. My issue was also a poorly working accelerator pump. I would call Lyc and send the carb back. You will need and A&P to fill out the paper work I suspect. My theory assumes that everything worked fine prior to the overhaul! PM me with your email and I will send you the service manual for the carb.
Bill

About 15 years ago, I had the same problem with brand L.

But, all the way back to the first message ... I think the jet solves the stumble problem, but does it solve everything? Also, it wasn't clear, but it seemed to read that the engine was running okay until the wash job in September.

Is there more going on here?

Dan

DanBaier said:

About 15 years ago, I had the same problem with brand L.

But, all the way back to the first message ... I think the jet solves the stumble problem, but does it solve everything? Also, it wasn't clear, but it seemed to read that the engine was running okay until the wash job in September.

Is there more going on here?

Dan

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That is correct Dan, I think those informations are crutial. The engine worked flawlessly untill my last flight of september. After washing the plane (no air vent plug on unfortunately ) it stumbled on takeoff - first time that happened there... then yesterday, after the oil change... I'm suspeting water somewhere....

lockeed said:

I drainned the tanks from the drain under both wings. But I haven't drained the gascolator - didn't tought about it. I have experience with car mechanic, but items like the gascolator are new to me.

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Dear Lockeed, I'm guessing that you did not build this aircraft. Consequently you may have neither the knowledge nor legal right to perform any firewall forward maintenance.

On that basis I recommend that you seek the services of a registered Aircraft Maintenance Engineer and get to the bottom of your problem before further flight. It is always possible that your faltering engine is telling you that there is some greater problem looming.

Asking for advice on VansAirforce is fine but I suspect this matter may be beyond you and that you would be better served by dusting off your chequebook.

Then. when you know what your engine fault is, you might like to report back here so that we can determine the winner of the "spot the problem" contest.

Captain Avgas said:

Dear Lockeed, I'm guessing that you did not build this aircraft. Consequently you may have neither the knowledge nor legal right to perform any firewall forward maintenance.

On that basis I recommend that you seek the services of a registered Aircraft Maintenance Engineer and get to the bottom of your problem before further flight. It is always possible that your faltering engine is telling you that there is some greater problem looming.

Asking for advice on VansAirforce is fine but I suspect this matter may be beyond you and that you would be better served by dusting off your chequebook.

Then. when you know what your engine fault is, you might like to report back here so that we can determine the winner of the "spot the problem" contest.

Click to expand...

I'd love to do it. One major problem:

Nearest A&P is in Quebec City - which is 700km (450 miles) away.

If I need to take the carb off and disasemble it, I'll do it. If I need to take the engine off, put it on my engine stand and take it appart. I'll do it too.

There is a thing or two that might be new to me, like the gascolator, but apart from that - this 1950 design is pretty darn simple... I've solved mechanical and electrical problems on modern cars and various vehicules that were far beyond a bad hose, a faulty carburator or debris in the delivery lines...

There is a lot of things that have been beyong me, but none that I haven't solved. (don't want to sound pretentious) I'll get to the bottom of this... and learn a few things in the process. Using my check book will not teach me anything.

You may or may not have another problem. But you do have a carb that is known to stumble.

I'd love to get a list of parts, needed to convert to the 10-4164-1 specs.

lockeed said:

If I need to take the carb off and disasemble it, I'll do it. If I need to take the engine off, put it on my engine stand and take it appart. I'll do it too.

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I suspect that what you are proposing to do will be illegal so it might not be such a good idea to advertise your intentions on a public forum. Nor would it be a good idea for other builders on this forum to encourage you as any subsequent accident resulting from illegal maintenance may reflect unfavorably upon the Experimental Category at large.

lockeed said:

I'll get to the bottom of this... and learn a few things in the process. .

Click to expand...

I just hope that your learning experience is not an unpleasant one.

Captain Avgas said:

"...you may have neither the knowledge nor legal right to perform any firewall forward maintenance...."

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At least in the US, anyone has the "legal right" to work on an experimental aircraft - no certificate of any kind is required.

I still think the best thing to do is get the aircraft where it is above freezing for a day or so, and then start trying to drain water - tanks, gascolator, fuel filters (if installed), etc. I think from the message, we assume AvGas with no additives. If that's not the case, then drain everything and replace with that. Really, I think before taking things apart, try the simplest approach.

As to the stumble, it should be addressed, but I can't begin to tell you how many brand L powered aircraft there are out there that have this same condition.

Dan

Captain Avgas said:

I suspect that what you are proposing to do will be illegal so it might not be such a good idea to advertise your intentions on a public forum. Nor would it be a good idea for other builders on this forum to encourage you as any subsequent accident resulting from illegal maintenance may reflect unfavorably upon the Experimental Category at large.

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Bob - Please note that the man with the problem is in Canada. It is completely legal for him to do all the work on his amateur-built aircraft, and do all sign-offs on this work, and all sign-offs for annual inspection, etc, as long as he is the owner of the aircraft. This is covered in CAR 571.11(2)(b).

Whether he has the knowledge and experience required to properly do this work is another question, but he is perhaps the best placed to determine that. He just needs to keep in mind that this isn't a car and that mistakes can kill.

I've been part of the ultralight world for quite a while guys, I know about "owner's maintenance" and safety.

I'm probably one the most critical and perfectionist guy you'd ever meet - note that the aircraft hasn't flown since September - not that I couldn't. But I wanted to get to the bottom of this before doing so... Been very busy since then, so it sat there for 4 months.

Now I wanted to get as much input as possible before heading back to the hangar to diagnose the problem - and forum like VAF is a great place to meet people with knowledge about those typical problems.

I will not fly the plane untill it perform flawless on the ground, period.

On the other hand, any of you guys have a solution to get access to the gascolator easily? A door under the lower cowling, a drain tube extention?

An extension to the gascolator through a small hole in the bottom of the cowling is your best solution. It does not even have to extend through, flush would work.

From rereading your original post, I don't think there is anything wrong with your airplane other than having not the most desirable carb setup.

I've seen this even on certificated aircraft where a smooth application of throttle will cause a stumble around 1400 RPM.

Your best bet is to call a carb shop and talk to them about the differences between the two part numbers, and see what they would charge you to change the carburetor over.

See this thread, you need the A666-660 kit:
http://www.vansairforce.com/community/showthread.php?t=30424

DanBaier said:

At least in the US, anyone has the "legal right" to work on an experimental aircraft - no certificate of any kind is required.

Dan

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Are you saying that anyone can buy a completed Experimental aircraft in the US and Canada and do all of their own maintenance despite possibly having zero understanding of aircraft systems....and then go and fly that aircraft, possibly IFR in controlled airspace.

If that is the case then it seems to me to be an amazing situation. It certainly isn't the situation here in Australia. Over here you need to have built at least 51% of an Experimental aircraft to be able to fully maintain it and do condition inspections.

Yes that is the case, at least in Canada. At first glance this does not seem to be a desirable situation, but long term stats have not shown there to be any significant issues. At least that is my understanding.

Anyone can maintain/work on an experimental and sign for it, a repairman certificate or A/P is required only for the condition inspection.

It is kinda scary sometimes

Captain Avgas said:

Are you saying that anyone can buy a completed Experimental aircraft in the US and Canada and do all of their own maintenance despite possibly having zero understanding of aircraft systems....and then go and fly that aircraft, possibly IFR in controlled airspace.

If that is the case then it seems to me to be an amazing situation. It certainly isn't the situation here in Australia. Over here you need to have built at least 51% of an Experimental aircraft to be able to fully maintain it and do condition inspections.

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Yes, that is the case here in Canada. And people can work on their own cars too, and then drive them at high speed only a few feet away from other vehicles, pedestrians, buildings, etc, with with no medical requirements either.

I've never figured out why we go over the top on general aviation regulation, but just accept a certain loss rate when it comes to automobiles.

Kevin Horton said:

Yes, that is the case here in Canada. And people can work on their own cars too, and then drive them at high speed only a few feet away from other vehicles, pedestrians, buildings, etc, with with no medical requirements either.

I've never figured out why we go over the top on general aviation regulation, but just accept a certain loss rate when it comes to automobiles.

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+1

From what I understand - in Autralia, even if you've built ultralights and experimental aircraft in the past - but haven't built the one you just bought, you wouldn't be able to maintain you own aircraft even if you have the skills and knowledge to do it per that 51% rules. Taken this way....it's a stupid law.

Still, what I would like to see one day is a mecanical certificate - same as the radio operator certificate, that would enable someone to get the basic knowledge to legaly maintain their own aircraft. This could be a 5 day group course or something like that... which would cover the basics...Engine, fuel system, electric system, control and hardware...

This could be a 5 day group course or something like that... which would cover the basics...Engine, fuel system, electric system, control and hardware...

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And to think I wasted 6 1/2 years at an aviation university. Wow, I could'a had a V8.

aerhed said:

And to think I wasted 6 1/2 years at an aviation university. Wow, I could'a had a V8.

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Don't know what you meant by that message, but I obviously was talking about basic maintenance knowledge that experimental and ultralight owners would greatly benefit from. A form of recognition of competence that would enable you to maintain a relatively simple aircraft yourself.

Not talking about learning all the intricate workings of a PT6 turbine over a weekend....

Anyway, back on track....

Just kidding around, but I think your idea might work if it was specific instruction on a specific plane. I don't know how you'd deal with alterations and repairs and such. As a side note, a US mechanic can't bust open an instrument or a prop, etc. while a homebuilder can do so without thinking twice.

Yep, that's very weird too... I guess we should all enjoy the freedom we have as experimental owners...! ....or "expert-or-mental" airplane owners...

Kevin Horton said:

Yes, that is the case here in Canada. And people can work on their own cars too, and then drive them at high speed only a few feet away from other vehicles, pedestrians, buildings, etc, with with no medical requirements either.

I've never figured out why we go over the top on general aviation regulation, but just accept a certain loss rate when it comes to automobiles.

Click to expand...

Kevin, you make a good point and I agree with you. I've argued the same point myself.

But in the end I think commonsense dictates that it comes down to the type of flying we do. Surely if we have the privilege of sharing controlled airspace with high capacity RPT it stands to reason that there needs to be some basic controls in place in terms of flying skills, medical condition, and aircraft maintenance.

Outside of controlled airspace I personally don't think it matters. In that environment people in recreational aviation should be basically free to take whatever risks they assess to be personally reasonable (as they do with their automobiles).

lockeed said:

Yep, that's very weird too... I guess we should all enjoy the freedom we have as experimental owners...! ....or "expert-or-mental" airplane owners...

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I think you do just fine with English... better than most natives in these Oklahoma parts! You are also helping some of us neophyte builders who have much less knowledge and experience learn from the master builders on the forum! Keep up the good work y'all!

Roger Pierce
Tulsa, OK
RV-10 fuselage (still)