Jabiru 2200 (1st gen) spark plugs fouling - too much oil in rocker chamber @ idle RPM

[MarcoP]

Hi all,

here I am with my 2nd post (introducing myself here) looking for opinions on the problem is driving me crazy since 1 year now.

(it's a long post, to have a short version jump down to the blue part and read that one only)
 

I'm new to ultralight piloting and not a mechanic at all, but i like to read and learn about things i am passionate so i'm quickly learning while getting fouled by doubts and questions too. FOULED.. that's the word! 1 year ago I purchased a Fly Synthesis Storch CL powered by a 1st gen Jabiru 2200. In a matter of 20 Hs I experienced a very hard RPM drop during mag test: 1 cylynder was off with 1 mag off. I checked the spark plugs and some were oil fouled.

So i took my baby to the doctor (certified Jabiru service) who had a deep look at it and gave me the bad news: no service bulleting has ever been done here, pistons are not Jabiru's ones, valves and guides needs replacement, there's a oil recovery system which goes directly in the sump (with no even oil/air separator), etc.. etc.. long story short: let's do a top-end overhaul even if it's a little early (800 Hrs on the engine) and apply all (well, not all, but most of) the bullettins . So we did: 2 months (and a LOT of money) later i got my baby back and happily flown 25 hours down to the 1st periodical check after the overhaul (and run-in oil replacement, all done by certified Jabiru mechanic).

After the run-in period (less than 5 hours later) I experienced the fault at mag test again.

It recalled in my mind i was doing some "gliding" at the nearby mountains just 15 before landing (storch has a good glide ratio and i'm an ex glider pilot so..) and to do that i was keeping my engine at idel for a while. Now that i was thinking about it: i did just the same when it happened the first time: several minutes idling to practice emergency approaches.

I talked with my mechanic, cleaned spark plugs, tested again and all went good for more or less 5 Hrs, then AGAIN: 1 mag dropped more than 200RPM: applying 10 seconds of full throttle while on full brakes did the trick to clean the sparkle plugs this time, so i wanted to try by changing all the spark plugs with new ones and give it some more testing, 3 Hrs later it happened again, this time it happened while flying (after a couple of minutes idling) and cylinder 4 completely shutted off (CHT and EGT falling down as fast as hell while engine performing rough. Likely my plane is capable to fly safely home with 3 cylinders only.. so it got me home.

After another long talk with the mechanic we decided to put new spark plugs (iridium this time) just to get there and investigate it deeper. So we did.

The whole fly has been ok, 2700 RPM (which gets me quite close to my max allowed speed: 160 km/h on 180 VNE) and the doctor outcome has been:

- there is oil in the combustion chamber of cyl #4, indeed.. we'll replace the rings once more.

- there is a coil which is not working perfectly, we'll replace the coil (i insisted to replace both of them + all cables + all spark plugs again).
... so we did, another good amount of money later i was happily flying home (2 hours fly).

Just 1 flight later (1 more hour) after getting it home I had to perform a quite long idle approach to land (this plane is almost a glider, it never gets down, flaperons are not that much effective as breaks.. he really wants to fly!) and guess what? Fouled plugs (iridium) on cyl #4 again.

So let's recap:

• freshly overhauled (cyls have been rectified, new pistons, new valves (double springs), new guides, rectified valve seats @ the heads, etc..)
• changed plugs several times
• changed coils and cables
• changed rings twice

 

I came across several readings and my attention went to the higher side of the engine (as cyl/piston/rings are fresh!) I've been attracted by a video about the amount of oil in the rocker chamber and the whole discussion about the internal pressure issues (but those were about Gen 2 engines).. I know you know what I'm talking about, many of those readings where in this forum, this one as example.

Some more interesting readings i've found:

• THIS is quite an interesting article, but looks a little hardcore to me, involving guides, oil cooler, complete oil re-routing and using carb intake to get some depression in the oil sump. It is in both French and English language a little under the French.
• Even if JSB013-1 is for 2nd gen engines only (mine is 1st) I was wondering if the same concept may apply somehow. 
• This, This, and This too are 3 pages from the same guy who had the opposite problem but ended up investigating the same region of the engine trying to fix oil feed up there.

 

So I decided to run the "trasparent test" myself and I found that the rocker chamber gets full of oil when at idle ! Here you are the video, interesting things happening at 2:10


What's your opinion on that?
Could PCV be a valuable try?
What about an "expasion" oil sump (i am on the "small sump" of gen 1) 
Have you ever experienced this?
 

@FACTHUNTER i'm looking at you with great hope! From what i understood, reading at you, it looks like to me that you are the one sticking to the "hard but safe path" like a jedi, instead of going for quick and furious patching of the problem, creating another one in the near future.

Edited Monday at 02:58 PM by MarcoP

[Bernie]

Video won't open for me.

Bernie.

[MarcoP]

lets retry:

 

 

 

[facthunter]

Oil flooded rockerbox will cause your problem. Engine idling will make it worse.  (draw the oil down the inlet valve guide). The oil is not draining back. I vaguely recall the need for a bleed hole at the top of the box. Check all SD's.  Don't run your engine at high power uncowled.  It will overheat.    Report back   Nev

[Moneybox]

I know nothing about these engines but I can't see the connection between an oil flooded rocker box and fouling the sparkplugs unless the valve guides and seals are a problem. There's no other way this oil can get to the combustion chamber. It could come right back to fuel mixture or fuel type causing the spark plug problem. Any sparkplug not firing correctly can appear oiled up. Are your sparkplugs the correct heat range for the job?

Edited Tuesday at 12:00 AM by Moneybox

[440032]

57 minutes ago, facthunter said:

Oil flooded rockerbox will cause your problem. Engine idling will make it worse.  (draw the oil down the inlet valve guide). The oil is not draining back. I vaguely recall the need for a bleed hole at the top of the box. Check all SD's.  Don't run your engine at high power uncowled.  It will overheat.    Report back   Nev

That bleed hole thing has nothing to do with this engine. It's not applicable.

[facthunter]

Why is that? Is there any harm in checking the SD's?  It's NOT ok to have oil filled rockers. Nev

[440032]

Marco - you don't say what fuel you are using.

I just had sooty black spark plugs with RPM drop at mag check after running unleaded petrol/mogas for maybe the last 13 hours. Spark plugs about 83 hours use, first 70 on avgas.

I'm going back to avgas use only with (570 hours satisfaction.)

[440032]

Just now, facthunter said:

Why is that? Is there any harm in checking the SD's?  It's NOT ok to have oil filled rockers. Nev

The rocker chamber vent Service Bulletin does not apply to solid lifter engines.

[facthunter]

You tell ME why there's so much oil there then.  Nev

[Moneybox]

10 minutes ago, facthunter said:

You tell ME why there's so much oil there then.  Nev

My guess is that it's always there. I don't know the engine but perhaps the oil return is via the pushrod tubes? Most people would have no idea what goes on under the rocker cover during normal operation because we can't see in there. 

[facthunter]

Sorry, but that reply is meaningless. . The oil return is by the pushrod tubes and they should easily handle it. Nev

[Siso]

Can you just drill a small hole in the top of the perspex and see what happens.

[facthunter]

It may be feeding too much oil. Nev

[kgwilson]

The evidence shows the oil is getting in but not out. I can't see what Avgas/Mogas has to do with it. Most Jabs I know (Gen 1 to 4) run exclusively on Mogas (Automotive petrol 98 RON). Plugs will always appear black but I've never known them to foul. Avgas on the other hand can lead to lead deposits on the piston crown, head & plugs. There would appear to be a problem with the oil return & if this is via the pushrod tubes & the pressure builds up it will find its way into the combustion chamber, new guides or not & will be worse at idle RPM. Find the oil return blockage and job done.

[BrendAn]

i wonder if he keeps the oil on the full mark on the dipstick.  

[facthunter]

They usually vent a bit of oil when you do that. Nev

[kgwilson]

Top up to the full mark & your oil catch bottle will get most of it. Best to top up to about 3/4 of the way up the knurled section of the dipstick (for the 3300 6 cyl). My Gen 3 3300 drops about 3mm on the dipstick between changes every 25 hours with no top ups required.

[Red]

6 hours ago, Moneybox said:

I know nothing about these engines but I can't see the connection between an oil flooded rocker box and fouling the sparkplugs unless the valve guides and seals are a problem. There's no other way this oil can get to the combustion chamber. It could come right back to fuel mixture or fuel type causing the spark plug problem. Any sparkplug not firing correctly can appear oiled up. Are your sparkplugs the correct heat range for the job?

Jabs don't have guide seals.

[Thruster88]

Oil consumption would have to be very high to cause plug fouling. A Rotax 582 can eat 400ml of oil per hour no problem. Perhaps the real problem is a weak ignition, just a thought. 

[Thruster88]

Reading marko's initial post, he flew 25 hours since the rebuild but didn't say what if any oil consumption was.

[Moneybox]

54 minutes ago, Thruster88 said:

Oil consumption would have to be very high to cause plug fouling. A Rotax 582 can eat 400ml of oil per hour no problem. Perhaps the real problem is a weak ignition, just a thought. 

 

Yes I agree, I think you're trying to resolve a problem that's not there. However if there are no valve seals and if that oil level in No.4 is abnormally high perhaps it can feed oil down the intake valve guide. I'd be looking for other reasons for the plug fouling, fuel, spark or sparkplug heat range. If its burning enough oil to foul the plugs in a short period of time then there'd be a lot of blue smoke.

[facthunter]

It was doing long approaches at idle. Plenty of motors don't like that. Pistons get loose. Inlet valve guide fit has to be good and can be .001" if the finish is good and parallel. The exhaust needs more  and could also pass oil on a glide. Yes oil (and air can go back in if the flange leaks.)  When power is on, some of  the gas goes UP the exhaust guide and contaminates the rocker box. EXCESS oil can lower the Octane and cause detonation. Nev

[Blueadventures]

14 hours ago, MarcoP said:

lets retry:

 

 

 

Send video to Jabiru at Bundaberg and ask them. I'm sure they will reply.  Cheers.

[Red]

Here is the relevant SB for the Rocker box vent

 

https://jabiru.net.au/wp-content/uploads/2018/05/JSB013-1.pdf

 

 

 

Take note of section 3, copied below

 

 

 

 

Jabiru Service Bulletin: Jabiru 2200 Engine Rocker Chamber Vent
JSB 013-1 8th August 2006
JSB013-1.doc Page 2 of 5
3 Background
The upper valve train of Jabiru engines is lubricated by means of a low-pressure feed which
supplies oil to the valve guides and rockers, then flows back into the sump via the pushrod
tubes.
In the engines listed above the flow of oil back into the sump can be reduced by internal airflow
and pressures inside the crankcase. This effect is magnified by a build up of negative pressure
inside the rocker cavity (as air is drawn out of the rocker cavity by the normal leakage past the
intake valve guide) and by the additional oil flow from the hydraulic lifters.
This restriction in the amount of oil flowing back into the sump leads to the rocker cavity filling
with oil. As the rocker cavity is at a high temperature (typically over 130° Celsius) the oil is
overheated, becoming very thin and gradually loosing it’s lubricating properties. This leads to
increased upper valve train wear (valve guides, rocker bushes etc) and elevated oil
consumption as the thin oil is sucked down the intake valve guides and burnt in the engine. In
some cases oil may also be found in the induction manifold.
This phenomenon varies from engine to engine due to differences in operating regimes,
different average oil levels in the sump, different engine vent outlet pipe positions and different
levels of blow-by past the piston rings. Jabiru 3300 and 5100 engines (including 3300 engines
with hydraulic lifters) do not suffer from this problem due to the larger airspace volumes in their
crankcases and oil sumps.
Drilling a small vent hole inside the rocker cavity removes the negative pressure inside the
rocker cavity and allows the oil to drain normally into the sump (Note that as the pressure inside
the cavities is generally less than ambient, air is sucked in through the vents – only negligible
amounts of oil flow out). The following Service Bulletin details the installation of the rocker
cavity vent and ways to manage oil consumption before and after the vent is added