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Cylinder #1 firing issue

Erimo

Well Known Member
My aircraft is finish and I?am waiting for the ?permit to fly?. So I only ran the engine 6 times and taxi 2 times.Engine timer is 1 hour and 1/2.
Today, after 2 weeks without running the engine I made a start and warm up, for the first time with cowls.
I found that even if the engine has started well, it did not turn perfectly (rough and even at some engine speeds, ?misfires?).
Pmag L : -150 RPM / Pmag R : -150 RPM
Findings: CHT and EGT of cylinder # 1 lower than others: CHT max 111 ? F for 250? to 280 ?F on other cylinders. EGT less than 1000 ? F against 1200 ? F.
Engine stop after 10 minutes.
During firt starts and warm-ups : temperatures substantially identical on the 4 cylinders.
Engine : IO-390 exp, new, from "Van's". Two Pmag (timing controled today, 2? after TDC).

Have you suggestions ?
 
Did the roughness appear with the low CHT on #1? If not, I would be checking the wiring/connections on the CHT sensor.

If yes, It is easiest to start with ignition issues for a sudden appearance issue like this. The RPM drops seem high for the Pmags, which I thought had agressive timing in lower RPMs. Given that both sides have a large drop, I would be looking for an issue on both of them. If the problem were isolated to one side, you should be seeing drops of different amounts. You need to check your plugs and your wires. I have also read several posters talking about ignition leads that were not pressed onto the coil hat of the Pmag tight enough, causing misfires.

I would also check the injector on #1. A new system is more likely to have debris break loose and clog the injector.

Larry
 
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Hi Larry,

CHT and EGT are lower than other three cyl.: the senders are different. The engine is continuous rough. Pmags are timed per the manual. I checked ignition leads, coils hats. I remove the injector fuel line from fuel spider and the injector : normal flowing in them. Tomorrow I'll check spark plugs.
 
Engine : IO-390 exp, new, from "Van's". Two Pmag (timing controled today, 2? after TDC).

Have you suggestions ?
Not saying that this is your issue but your timing is incorrect for the IO-390 which the designed timing is at 20 BDS and not 25 like IO-360 is. So with PMAG you would want at least 5 degrees pass TDC, and if you are below version 40, maybe 6-7 degree pass TDC.
You also may want to limit your ground run up once you are satisfied that all is in good working order. It is not good for your engine till it is broken in.

Good luck.
 
If you have toggle switches and one was grounded or a key switch with the jumper in to keep one ignition grounded while starting AND your P-mags are pre-version 40, there is a very good chance one P-mag lost it's timing mark.

As mentioned above by Mehrdad, angle valve engines should be timed at 20° BTDC. The jumper in A curve starts at 26.6° and advances to 35°. Leave the jumper out and it starts at 30.8° and advances to 39.2°. Both the A & B "curves" are way too much advance for any angle valve and the jumper in A curve is marginal for a standard compression parallel valve engine.

You have three choices, clock the P-mags, change the configuration with the free EICAD program from Emag, or install an EICommander.

Clocking the P-mags is probably the worst option of the three. The EICAD program works well but lacks the monitoring functions of the EICommander.

If you use the EICAD program or EICommander, set the Advance Shift to a -7.0 and the Max Advance to 26.6. If you do this and then set your P-mags to Top Dead Center, your P-mags will fire at 19.6° for takeoff power and only advance out to 26.6° as you climb.

Regardless of how you want to set your timing, if your P-mags are not at least up to version 40, send them back to the factory for the upgrade. I know that you are in France and it is a pain to do that but it should be done.
 
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PS. You might want to take the time to watch the video listed in this thread.

It talks about timing, ignition basics, etc. At the end there some discussion about P-mag timing.
 
Hi Larry,

CHT and EGT are lower than other three cyl.: the senders are different. The engine is continuous rough. Pmags are timed per the manual. I checked ignition leads, coils hats. I remove the injector fuel line from fuel spider and the injector : normal flowing in them. Tomorrow I'll check spark plugs.

CHT's that low means you are not making a lot of power in that cylinder. This can be consistent low power per cycle or intermittent cycles of full power and no power (i.e. misfire). Both CHT and EGT are averages across cycles and therefore not definitive here. Is the roughness consistent or does it vary in it's roughness? The former points to a valve or ring issue (possibly mixture) and the latter to an ignition issue. Both can show similar results on the CHT/EGT.

Once you confirm that your mixture is good (i.e. good fuel flow through the injector) and you are getting regular spark (an easy test here is to put an automotive timing light on each of the #1 plugs and confirm that you get steady flashing without interruption - timing light only lights up if plug fires). that is not severly out of time, next is to look for other causes of reduced power. Possible candidate are a valve issue or a ring issue. Valves more likely. Step one is a leak down test (i.e. compression test) to be sure that your valves are closing fully and without cracks or blockages that prevent full closing. If you are leaking, the test will tell you where the problem is - Rings, In valve, Ex valve. Step two, if no evidence from step 1, would be to visually examine that the In valve on #1 is fully opening by measuring the lift at the rocker. Simply compare to a known good cylinder.

Don't worry about the exact timing yet. Anything between 10-40* will run smoothly, especially at low or middle RPMs. It takes timing well out of this range to cause roughness, excluding detonation of course, but you shouldn't see that at low to mid RPM levels. It is a good bet that your roughness is from whatever is going on in #1 and not an overall timing issue.

EDIT: forgot to mention that it would be a good idea to pull the cover off the spider and confirm there is no debris in the small "V" orifice on the port leading to #1 injector line. I would do this if the leak down comes back clean.

Larry
 
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I'm thinking that valve issues on a new engine would be rare.

If only cyl #1 is showing bad numbers, I would look to fuel flow to that cylinder. I assume fuel injection? Trash in the injector or spider? Next would be ignition. Bad plug?

Look for the "cheap fixes" first! :rolleyes:
 
Not saying that this is your issue but your timing is incorrect for the IO-390 which the designed timing is at 20 BDS and not 25 like IO-360 is. So with PMAG you would want at least 5 degrees pass TDC, and if you are below version 40, maybe 6-7 degree pass TDC.
You also may want to limit your ground run up once you are satisfied that all is in good working order. It is not good for your engine till it is broken in.

Good luck.

Ok. I'll correct the timing from 2? to 6? past TDC #1.
 
If you have toggle switches and one was grounded or a key switch with the jumper in to keep one ignition grounded while starting AND your P-mags are pre-version 40, there is a very good chance one P-mag lost it's timing mark.

As mentioned above by Mehrdad, angle valve engines should be timed at 20? BTDC. The jumper in A curve starts at 26.6? and advances to 35?. Leave the jumper out and it starts at 30.8? and advances to 39.2?. Both the A & B "curves" are way too much advance for any angle valve and the jumper in A curve is marginal for a standard compression parallel valve engine.

You have three choices, clock the P-mags, change the configuration with the free EICAD program from Emag, or install an EICommander.

Clocking the P-mags is probably the worst option of the three. The EICAD program works well but lacks the monitoring functions of the EICommander.

If you use the EICAD program or EICommander, set the Advance Shift to a -7.0 and the Max Advance to 26.6. If you do this and then set your P-mags to Top Dead Center, your P-mags will fire at 19.6? for takeoff power and only advance out to 26.6? as you climb.

Regardless of how you want to set your timing, if your P-mags are not at least up to version 40, send them back to the factory for the upgrade. I know that you are in France and it is a pain to do that but it should be done.

The jumper was installed and I didn't remove it. You think I have to remove it if I well understood ?

Thank for the webinar.
 
look for a piece of FOD in the injector on that cylinder. This is very common. Then pull all four lines off the injectors and insert them into identical water bottles (empty). Balls to the wall, turn the boost pump on. Run for a while and see if the bottles have the same amount of fuel in them when finished.

I am not a fan of long ground runs on new engines. Others disagree, but if you find your oil consumption remains high after a few hours of flying....you'll know why. Test cells are a great start...but break in is not over that quickly.
 
I'm thinking that valve issues on a new engine would be rare.

If only cyl #1 is showing bad numbers, I would look to fuel flow to that cylinder. I assume fuel injection? Trash in the injector or spider? Next would be ignition. Bad plug?

Look for the "cheap fixes" first! :rolleyes:

I remove spider injector line and injector #1 himself : they are clear, and when the boost is ON, there is a fuel flow (same on #3).
 
The jumper was installed and I didn't remove it. You think I have to remove it if I well understood ?

Thank for the webinar.

No, but you need to understand how the P-mag timing works.

If you have the jumper in, you start at 26.6? before top dead center. To get it down to 20?< yo need to clock it 6.6?.

My recommendation is to connect to the P-mags with a computer and change the Advance Shift and Max Advance and then set them to Top Dead Center.
 
No, but you need to understand how the P-mag timing works.

If you have the jumper in, you start at 26.6? before top dead center. To get it down to 20?< yo need to clock it 6.6?.

My recommendation is to connect to the P-mags with a computer and change the Advance Shift and Max Advance and then set them to Top Dead Center.

Yes, understood. I re-timed the Pmag tonight, between 6 and 7? after TDC.
The spark plugs were black (only ground runs full rich), and oily only on cyl #1.
 
oily only on cyl #1.

Not surprising, as something is going on in there. Most likely scenario is broken rings. Second would be a problem with the valve guides. The leak down that I recommended will point you in the right direction.

Larry
 
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Not surprising, as something is going on in there. Most likely scenario is broken rings. Second would be a problem with the valve guides. The leak down that I recommended will point you in the right direction.

Larry

Or may be it's only (I hope that) a new engine normal oil consumption, but not burned due firing issue !?
Spark plugs were all black, but dry on other cylinders.
 
Or may be it's only (I hope that) a new engine normal oil consumption, but not burned due firing issue !?
Spark plugs were all black, but dry on other cylinders.

After the first hour on a new engine, the plugs should not have visible oil on them. Once you glaze the cyl walls, you will get oily plugs and pooling oil, but this won't happen until the cross hatch fills with coked oil (that is what glazing is). I am guessing that you haven't got things hot enough to glaze yet. Until the rings seat, they will leave excess oil on the walls that burns off during combustion. This is the high oil consumption seen prior to ring seating.
However, under normal circumstances this oil is not excessive and should not result in oily plugs; as evident by the other 3 dry plugs. You have something else going on in there.

Your engine used to produce normal combustion and therefore normal heat levels, so this would have burned off the excess oil on the plugs from initial assembly. After that initial burn off, the plugs shouldn't be oily even if the cyl is not firing. If this is a misunderstanding on my part, then you may be right.

It's clear from the CHT data (assuming sensor is good) that your #1 is not producing a lot of power. The oil helps to confirm the problem. The most common ways to get oily plugs is a problem with the ring/wall interface or problems with your valve guides. A blocked oil return from the rocker box can also do it.

Again, you need to get a timing light on the #1 plugs to confirm whether or not they are regularly firing. You also need a compression test on #1, unless you find that glazed cyl walls are present, which would explain the oily plugs, but I would do it anyways. This can typically be observed by looking through the spark plug openings.
 
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cylinder woes

If the engine came from Vans, the cylinders had some left over preservative in them from Lycoming. Proper pre-oiling of the engine also will foul the lower plugs but sometimes not all of them. I would clean the plugs, re-install and do a short ground test.
 
Magnus, Larry and Allen,
I remove all spark plugs to clean them tonight, they were well fouled. The cyl #1 seems clean but there is a little amount of clear oil in the bottom (not burned). The wall is not glazed.
That seems to be a firing/ignition defect.

I swaped also the spark plugs, but I'll not be able to start the engine before thursday (because I go to the hangar only in the evening other days). But it will be a short ground test ....;)

Thanks for your opinions.
 
Please describe how you are setting the timing. If you are "clocking" your P-mags, how are you doing it?
 
Hello,

Finally, all the spark plugs were very fouled due to mixture too rich.
Hence the misfiring.
After cleaning plugs the engine runs well with Pmags timed 5? ATDC (sprk advance 20?) but I have to lean a little on ground otherwise it's rough.
I'll adjust mixture control.
After 2 hours of flight, there is always black soot inside exhaust pipe.
 
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