Cold Cylinder Mystery

[Yetti]

I think I would go like this.

If pull through shows all good.  Then checking timing. If timing is on.  Then fuel.

It almost sounds like the shear pin on the accessory drive gear has failed partially.  

Fuel inspection could be limited to Servo, Servo Screen, Fuel divider, injectors.

[RLCarter]

It will be interesting as to what you find, so keep us update.

[N201MKTurbo]

I would at least check the point gaps in the mag. Every time I've had intermittent mags, it was because the points had warn to the point that they won't open any more. You can adjust them, but they are relatively cheap, so if they are warn, just replace them. Also check that the bearings aren't loose by just trying to wiggle the cam.

[chrisk]

Dual mags, found on some J models, have been know to have issues due to the mounting hardware coming loose. I'd take a careful look at that.

 

http://macsblog.com/2012/11/is-one-and-half-mags-enough/

[jetdriven]

Change the star lock washers any time the mag hold down nuts are loosened, or if the last time they were changed is unknown.  

Also use the latest design of hold down clamps.

these things can kill you.  At an air race last year an RV-6 finished a race a little down on power, and leaking oil.  The right mag was sitting on the engine mount.  He had retimed his mags that morning and reused the star washers.  

[N201MKTurbo]

27 minutes ago, jetdriven said:

Change the star lock washers any time the mag hold down nuts are loosened, or if the last time they were changed is unknown.  

Also use the latest design of hold down clamps.

these things can kill you.  At an air race last year an RV-6 finished a race a little down on power, and leaking oil.  The right mag was sitting on the engine mount.  He had retimed his mags that morning and reused the star washers.  

I don't discount the importance of anything you said, but if his mag fell off after a few minutes of racing, he forgot to tighten it. It should stay on longer then that with no star washers!

[jetdriven]

It flew about an hour and a half.  

[INA201]

Hey guys, sorry for being slow on updating and thanks for all your feedback. I went out Sunday and pulled the engine through per Yetti's suggestion and everything was nice and tight.  Monday my mechanic pulled the nozzles to clean and did a flow test with little glass bottles.  The #2 cylinder was only getting 1/2 the volume of fuel than the others.  He sent the nozzles and the flow divider(spider) over to Airflow Performance based at our field KSPA http://www.airflowperformance.com/html/site_html.html.  Don at Airflow did spray testing on the nozzles and said that the nozzles are shot, need replacing. He is also going to rebuild the flow divider which should be done and installed tomorrow.  The mechanics were describing how this could result in the cylinders going cold based on the changing of the mixture when flow stops  or is restricted in one area making it lean while the others are going rich.  I didn't exactly get an explanation on what went wrong in the divider but hope to find out tomorrow afternoon.   I tried finding an event like this one in different forums but couldn't find a similar situation as this one.   The strange thing is that my EGTs, CHTs, and other engine data have always been relatively normal until this situation came about.  Hopefully, tomorrow, we can solve this mystery. 

[carusoam]

MS is a pretty powerful tool!

Congrats on finding the issue.

Good luck on getting it resolved.

Please report the next success.

Best regards,

-a-

[carusoam]

Keeping score... (Just for fun)

OP described situation on Friday at 3:03pm...

a PP (not a mechanic) collected the the first ideas to come in, and then provided...

" 

1) Checking fuel flow and distribution is somewhat easy.  Requires 4 identical glass jars and a timer... There is a typical gun solvent that is often used Hopps(?)"

At 3:49pm, less than hour later.

This grape vine is pretty good.

While your mechanic is cleaning out the blockage, try to catch it to help determine what it was/is.  It may belong to something that is disintegrating.  Something that you may want to know more about.

JPI data is something you can look back through to see if it was a problem on previous flights.  A speck of something (like a fuel hose inner layer bit?) can slough/sluff (sp) off and just show up and block flow.

Again, this is stuff I read here.  I don't have the mechanical knowledge myself.

Hoping it may help.

Best regards,

-a-

[INA201]

Man, what a great resource Mooneyspace is for solving issues like this one.  Thank you guys for taking the time to weigh in.  

At this point we have not seen any debris coming out of the fuel system.  I'm assuming they will purge the system prior to putting the new injectors on to make sure.  Carusoam, I have the older JPI700 but will find someone who can download the engine data to at least compare before and after the repairs.  

On another note, I had been gathering cruise speed, engine temp, fuel flow data on a modern mooney thread(inner gear doors)prior to installing the gear doors in a few weeks.  I guess I need to start over assuming this current problem is fixed.  It may be interesting to find out that cruise speed and other numbers improve and how they change with new Tempests vs 8 year old 500 hour Champions,  new injectors, and a rebuilt fuel divider.  

Again, thank you guys for all of your knowledge and insight.  I'm a new Mooney owner (4 months)who moved up from a Piper Archer after 7 years.  I've learned more on Mooneyspace already than would be possible through years of trial and error.  No slight to the Piper but the Mooney is flat out a "Real Airplane!" ... I still feel that she hasn't adopted me as her owner yet.

[N201MKTurbo]

I find it interesting that he said your injectors are shot. There is nothing to wear out in the injectors except for the threads and the wrench flats. They can get crud in them that will affect the flow, but that can always be cleaned. Unless someone damaged them by cleaning them wrong, which can only open up the openings and flow more, or screw up the spray pattern. The injectors are made up of four parts, you may be able to buy the individual parts.

BTW never clean the injectors by running a wire through them. I have found that acid brush bristles work good.

[N601RX]

New injectors from Lycoming are very expensive.  Here is a PMA source that is only $60 for a complete injector.  Gami is also a possibility if you have to have new ones.

http://www.avstardirect.com/products/view/425

[Yetti]

I have 4 mason jars at the hanger for testing.     I would want a better definition of "shot"   I would want to know what was the material that was plugging  and where did it come from.   Have there been any mechanical fuel pump failures recently?   Has the Fuel servo Screen been checked and cleaned?  What about the fuel flow measuring device?  Who installed and did they let crud get in?

[Browncbr1]

Soak the injectors in hopps.  Do the glass jar procedure 3 or 4 times without injectors attached to the lines. (After installing the rebuild spider) Verify equal distribution and no debris.   

 

Spiders have rubber in them.  I don't trust one that is more than about 10 years since rebuild.   They are super cheap to overhaul, for peace of mind.   Good luck!   Btw, I wouldn't take much stock in "worn out injectors".  

[jetdriven]

Put the injectors and the hoppes in an ultrasonic cleaner. 

[FlyDave]

I've been watching this thread since it started - interesting problem.

If an issue moves randomly from one cylinder to another with the same symptoms, from my troubleshooting experience, you need to back up to the last common potential source of that issue. I don't see the mags/harness/plugs as a potential because each mag drives one plug in each cylinder (cold cylinder means neither plug in a cylinder is firing). Having both plugs or high tension wires or mags randomly fail at the same time in different cylinders is statistically highly improbable (though not impossible). I think it's the spider and FOD either moving from one port to another (I don't know what these things look like inside) or small pieces of FOD are breaking off upstream of it and lodging somewhere to block fuel flow to different cylinders.

This is just my $0.02 but it will be interesting to see what finally resolves the issue, that is if they find a smoking gun.

[Shadrach]

 

I find it interesting that he said your injectors are shot. There is nothing to wear out in the injectors except for the threads and the wrench flats. They can get crud in them that will affect the flow, but that can always be cleaned. Unless someone damaged them by cleaning them wrong, which can only open up the openings and flow more, or screw up the spray pattern. The injectors are made up of four parts, you may be able to buy the individual parts.

BTW never clean the injectors by running a wire through them. I have found that acid brush bristles work good.

Over tightened B nuts can cause them to crack.

[INA201]

Guys, thank you for looking out for me on this.  My, mechanic texted that the plane is running great and ready to go.  However, after reading your posts I want to be more thorough at this point. I spoke with Don at Airflow Performance regarding this situation to get his thoughts.  As a reference Don does fuel injection systems for Bendix, many of the Van's guys systems, Sean Tucker, I've seen P-51s in his shop, etc. He has a great reputation.  He also rebuilt my flow divider.  Please keep in mind this is second hand information and being posted by a private pilot and not a mechanic.  

1.  The flow divider on his testing equipment was running erradically.

2.  The shields on the nozzles were flopping around and the nozzles showed wear and age from multiple cleanings.  Also they were 1978 vintage so needed replacing

3.  He recommended to check the fuel lines at the braise joint(im thinking this is right) under a magnifying glass to make sure they have no cracks in them where it is soldered to the line.  If so, to replace the lines.

4.  If the lines don't have any cracking on the joints then I need to clean them.  He said to clean the lines with carburetor cleaner onto a paper towel until no fuel dye or debris remain in the line.  After that to run brake cleaner through them to get the solvents out of the lines.  The lines will get dried up fuel dye in them from multiple cycles of the fuel boiling off through the line over many many years.

5. Check the screen on the fuel servo and if needed run it to his shop to ultrasonically clean it.  Check the gascolator screen as well for debris and if it needs it to also run it through the ultrasonic.

6.  The fuel servo is not related to this issue but i asked about his thoughts since it was 1985 since being replaced.  The way to test it is to run the engine up and get it warm, do mag checks, then to idle down to 900 or so RPM, turn on the boost pump.  If the pressure from the boost pump pressure changes the mixture then the servo needs to be looked at.

I will add to this that after all this is done I'm going to get the mason jars per Yetti's post and run gobs of fuel through just to be sure there is nothing left to come through.

Sorry for such a long reply.

[jetdriven]

Loose screens or screen caps renders the fuel injectors unairworthy.

There is a recurring AD with fuel injector lines and clamps, be careful with these, they can break if you are missing a clamp.

I wouldnt run that electric fuel pump more than a half a minute at a time, and keep it to a minimum. Its an 1800$ rebuild and people have burned theirs up emptying tanks with it, for example.

[Yetti]

As Jet driven said.  AD fuel lines.   If the rubber in the adel clamps is dried up and hard. Most likely is.  They need to be replaced.  While you are in there.....

Things that are good to know.

6.  The fuel servo is not related to this issue but i asked about his thoughts since it was 1985 since being replaced.  The way to test it is to run the engine up and get it warm, do mag checks, then to idle down to 900 or so RPM, turn on the boost pump.  If the pressure from the boost pump pressure changes the mixture then the servo needs to be looked at.

[Guest]

Anything after the finger screen in the servo to the tip of the fuel nozzle is suspect.  One thing not mentioned here is the age and condition of the fuel hose from the servo to the flow divider.  If it is breaking down internally it can clog a nozzle.

Look up AD 2015-19-07, Lycoming SB 342G, SI 1275C and SI 1532C  all pertain to fuel injection systems and are on the Lycoming web site.

Clarence

[INA201]

Looks like we all have worked this thing out. My mechanic had cleaned the stainless fuel lines as well.  The fuel lines connecting the servo, pumps, etc. are all newer Teflon and shouldn't be shedding any debris according to Bob at Carolina Flight.  All clamps on the stainless lines are relatively new so the AD was and is complied with and by logbook entry.  Screens all look good too.  

I was able to go out tonight and run her at different power settings, mag checks, taxiing around, switching tanks back and forth, and all seemed very solid.  I also did the fuel servo test and noticed no effect with the boost pump on or off.  The coolest thing was that during startup it fired off on the first compression stroke, usually takes a couple spins first.  Probably going to do another ground runnup prior to taking off again to be 100%.  

Thanks again everyone for all your posts and input it has been a great learning experience.

[Yetti]

The brown silicone hoses are the real deal.  The only step up is a stainless outer braid with teflon core.  Well shoot fire that was fun spending other people's mechanic dollars and group solving on the fix. :-)   You should be good for many happy flight hours for awhile.   I like a fast taxi or two and then some loitering over the top of the airport.

Edited January 8, 2016 by Yetti

[jetdriven]

Those brown hoses are stainless braid with a Teflon core.  Then an integral silicone jacket overall. They also have a smaller OD than the -124F style hoses and a tighter bend radius.