Cylinder 3 running about 50 degrees warmer than the others. IO-360-A1A

[sdflysurf]

Hope everyone is well!

I haven't posted in a long time, been enjoying flying the M20F with really no problems, until now.  Recently I got cylinder 3 warnings on the JPI over 400 and cylinder 3 seems to be running warmer than the others by about 50 degrees, and recently crept toward 450 degrees when climbing and so I brought it back in.  Here are the things we have done to diagnose/troubleshoot:

REMOVED #3 SPARK PLUGS, CLEANED & GAPPED. REMOVED AND SERVICED #3 INJECTOR. RE-INSTALLED SERVICED SPARK PLUGS AND INJECTOR.

 REMOVED AND REPLACED CHT PROBE #3 WITH NEW, P/N: 1260.

SWAPPED CYLINDER #3 AND #2 INJECTORS. LEAK TESTED, NO LEAK.  REPOSITIONED GROUND WIRE FOR THE JPI. FUNCTION CHECK SATISFACTORY.

REMOVED AND REPLACED BOTH #3 SPARK PLUGS WITH NEW, P/N URHM38E.

REMOVED & REPLACED #3 INTAKE GASKET WITH NEW, P/N: 654227.

 COWLING WAS CHECKED FOR PROPER COOLING CAPABILITIES – AND NO ISSUE WAS FOUND WITH THAT.

COMPRESSION CHECK: FIRING ORDER: 1-3-2-4 // COMPRESSIONS: 72-76-76-78. NORMAL PERAMITERS

 BORESCOPE: CHECK OK // NO SIGN OF GLAZING IN CYLINDER #3. CROSS HATCHING VISIBLE IN THE #3 CYLINDER.

 AT THIS POINT, IT IS SUGGESTED TO REMOVE AND REPLACE #3 CYLINDER.

Also I was told they flushed the spider (fuel injector system) and also swapped the fuel injector nozzle between 3 and another cylinder but the swapped locations were not affected leading me to think the nozzle is fine.  Any other things I should check or try?  Also do you recommend replacing with new cylinder or re-honing?  If any of you have done please let me know what to expect in cost/time and anything else I should expect to plan for.

THANKS ALL!

Edited September 9 by sdflysurf

[AndreiC]

Very interested in this topic. I also have a cylinder that runs much hotter than the others (by about 50 degrees), but mine is at a much lower temperature altogether (295-315 for cylinders #1, #3, and #4, 360-365 cylinder #2). Which of your cylinders peaks last when leaning? For me it is also the "problem" cylinder, #2. Since I generally run my engine at peak or slightly below peak (depending on altitude), this means my #2 cylinder is the richest, which kind of explains why it is the hottest.

Also, it seems you have high temps overall while climbing (I take it all your temps are close to 400 during climb). Have you checked your fuel flow at full rich? It should be around 18 gph at sea level or close. Anything less than that and you'll get hot CHTs during climb. I understand it is not hard to adjust the full throttle, full rich fuel flow.

You did not say what your temps are in cruise, and what leaning procedure you use (do you run ROP or LOP). Also, what speed do you use during the climb? In my E I try to climb around 115-120 mph IAS for best cooling.

I personally would not jump to replacing/overhauling the cylinder just yet. But others on this list may have other views.

[sdflysurf]

I hate to say that I don't have record of what it has been running at over the years consistently, but off the top of my head I would be around 380-400 on climb and then around 340-380 in cruise.  On a couple of hot days recently I got a couple of cylinders over 400 and the JPI gave me warnings, but cooled off in cruise.

How would you physically check fuel flow amounts besides the gauge?

Is there a way to adjust (add) fuel flow after the mixture knob at full rich (on engine) to see if that helps?

[EricJ]

53 minutes ago, sdflysurf said:

Hope everyone is well!

I haven't posted in a long time, been enjoying flying the M20F with really no problems, until now.  Recently I got cylinder 3 warnings on the JPI over 400 and cylinder 3 seems to be running warmer than the others by about 50 degrees, and recently crept toward 450 degrees when climbing and so I brought it back in.  Here are the things we have done to diagnose/troubleshoot:

REMOVED #3 SPARK PLUGS, CLEANED & GAPPED. REMOVED AND SERVICED #3 INJECTOR. RE-INSTALLED SERVICED SPARK PLUGS AND INJECTOR.

 REMOVED AND REPLACED CHT PROBE #3 WITH NEW, P/N: 1260.

SWAPPED CYLINDER #3 AND #2 INJECTORS. LEAK TESTED, NO LEAK.  REPOSITIONED GROUND WIRE FOR THE JPI. FUNCTION CHECK SATISFACTORY.

REMOVED AND REPLACED BOTH #3 SPARK PLUGS WITH NEW, P/N URHM38E.

REMOVED & REPLACED #3 INTAKE GASKET WITH NEW, P/N: 654227.

 COWLING WAS CHECKED FOR PROPER COOLING CAPABILITIES – AND NO ISSUE WAS FOUND WITH THAT.

COMPRESSION CHECK: FIRING ORDER: 1-3-2-4 // COMPRESSIONS: 72-76-76-78. NORMAL PERAMITERS

 BORESCOPE: CHECK OK // NO SIGN OF GLAZING IN CYLINDER #3. CROSS HATCHING VISIBLE IN THE #3 CYLINDER.

 AT THIS POINT, IT IS SUGGESTED TO REMOVE AND REPLACE #3 CYLINDER.

Also I was told they flushed the spider (fuel injector system) and also swapped the fuel injector nozzle between 3 and another cylinder but the swapped locations were not affected leading me to think the nozzle is fine.  Any other things I should check or try?  Also do you recommend replacing with new cylinder or re-honing?  If any of you have done please let me know what to expect in cost/time and anything else I should expect to plan for.

THANKS ALL!

Also check for an intake leak on that cylinder.   It's just a last-ditch thing to check, but it might be revealing.

[MikeOH]

One place to look for an intake leak is the O-ring on the intake pipe connection (opposite end of intake tube from cylinder)

[MikeOH]

@EricJ

#2 runs hottest on my engine, as well.  I'm down to thinking it's low full throttle fuel flow (IO-360A1A).  My understanding is that is a factory setting on the RSA5 fuel servo and is not field adjustable.  Do you know if that's true?  TIA!

[AndreiC]

1 hour ago, sdflysurf said:

How would you physically check fuel flow amounts besides the gauge?

Is there a way to adjust (add) fuel flow after the mixture knob at full rich (on engine) to see if that helps?

Does your JPI have fuel flow? My JPI-700 shows me fuel flow in gph, that is what I would be looking at. I usually see 18.5 gph right after takeoff, and it slowly goes down as I climb, even if I do not play with the mixture knob. As I pass 5000 feet or so I start to lean, trying to keep my EGTs around 1250-1275.

I was under the impression that the amount of fuel flow is a servo setting (not directly user accessible) which can be modified by a competent mechanic in the field.

[AndreiC]

7 minutes ago, MikeOH said:

#2 runs hottest on my engine, as well.  I'm down to thinking it's low full throttle fuel flow (IO-360A1A).  My understanding is that is a factory setting on the RSA5 fuel servo and is not field adjustable.  Do you know if that's true?  TIA!

Are you asking if the fuel flow to individual cylinders can be adjusted from the servo (and that yours may be set too low on #2)? Or are you asking about the overall fuel flow? I don't think individual ones can be changed in the servo; but changing injectors may?? I am not sure.

[sdflysurf]

1 hour ago, EricJ said:

Also check for an intake leak on that cylinder.   It's just a last-ditch thing to check, but it might be revealing.

We did this: REMOVED & REPLACED #3 INTAKE GASKET WITH NEW, P/N: 654227.

Is there anywhere else to check the intake for leaks on this engine?

[MikeOH]

9 minutes ago, sdflysurf said:

We did this: REMOVED & REPLACED #3 INTAKE GASKET WITH NEW, P/N: 654227.

Is there anywhere else to check the intake for leaks on this engine?

@sdflysurf

P/N: 654227 is the gasket between the intake pipe and the cylinder head.  I am referring to the other end of the intake pipe where there is a rubber O-ring.  Did you check/replace it?

[sdflysurf]

11 minutes ago, AndreiC said:

Does your JPI have fuel flow? My JPI-700 shows me fuel flow in gph, that is what I would be looking at. I usually see 18.5 gph right after takeoff, and it slowly goes down as I climb, even if I do not play with the mixture knob. As I pass 5000 feet or so I start to lean, trying to keep my EGTs around 1250-1275.

I was under the impression that the amount of fuel flow is a servo setting (not directly user accessible) which can be modified by a competent mechanic in the field.

My JPI is not connected to the fuel flow - only my steam gauge.

[MikeOH]

9 minutes ago, AndreiC said:

Are you asking if the fuel flow to individual cylinders can be adjusted from the servo (and that yours may be set too low on #2)? Or are you asking about the overall fuel flow? I don't think individual ones can be changed in the servo; but changing injectors may?? I am not sure.

My understanding is that NEITHER the individual injectors, nor the fuel servo can be field adjusted. Sure, you can try swapping injectors but they are not adjustable, nor is the fuel divider (spider).

[Ragsf15e]

8 minutes ago, sdflysurf said:

We did this: REMOVED & REPLACED #3 INTAKE GASKET WITH NEW, P/N: 654227.

Is there anywhere else to check the intake for leaks on this engine?

I would not change a cylinder based on what you said so far.  I would recommend putting a strong flashlight in the oil door then looking through the front of the engine and checking the baffles near #3.  My guess is a cooling airflow issue.  Are your cowl flaps opening all the way?  What is your climb speed?  I used 120mph in my F.  Fuel flow is important too~18.5 at sl is good.

with higher OAT in summer, your baffles, climb speed and fuel flow become much more important. 

 

[MikeOH]

@Ragsf15e

You saw 18.5 gph in your F???

Dang, that's likely my issue, as I never see much more than 17 gph, typically more like 16.5 gph.

[AndreiC]

2 minutes ago, MikeOH said:

@Ragsf15e

You saw 18.5 gph in your F???

Dang, that's likely my issue, as I never see much more than 17 gph, typically more like 16.5 gph.

I normally see 18.5 gph on takeoff in my E (same engine). My field is at 1000 ft MSL.

[201Mooniac]

6 minutes ago, MikeOH said:

@Ragsf15e

You saw 18.5 gph in your F???

Dang, that's likely my issue, as I never see much more than 17 gph, typically more like 16.5 gph.

I've often wondered about that as well, I've seen many saying 18+gph but on my IO360-A3B6D I typically see from 16.8-17.2.  No real temperature issues and my mechanic says it is fine so I've not worried much about it.

[Ragsf15e]

5 minutes ago, MikeOH said:

@Ragsf15e

You saw 18.5 gph in your F???

Dang, that's likely my issue, as I never see much more than 17 gph, typically more like 16.5 gph.

It was right at 18 taking off here in Spokane at 2000’.  It was closer to 18.5 at sl.

my new one is at 25.5, but that’s a whole different beast!

[MikeOH]

9 minutes ago, Ragsf15e said:

my new one is at 25.5, but that’s a whole different beast!

YOWZER!

That's like $2.50/minute...sounds like you miss your Eagle's fuel flow

[Ragsf15e]

8 minutes ago, MikeOH said:

YOWZER!

That's like $2.50/minute...sounds like you miss your Eagle's fuel flow

Well that was free.  Or at least it was for me.  The taxpayers took care of the fuel bill!

[Ragsf15e]

32 minutes ago, MikeOH said:

@Ragsf15e

You saw 18.5 gph in your F???

Dang, that's likely my issue, as I never see much more than 17 gph, typically more like 16.5 gph.

Here’s a screenshot from my Savvy data files on the F.  This is taking off from Grants Pass (~1000’).  Ff 18.3ish.

[carusoam]

When we want to know why one cylinder is running hotter than the others…

if we have a FF gauge, we can run a Gami spread test…

if we don’t have a FF instrument.. we can run the test, but may not get enough detail…

if air is leaking into a cylinder, or an injector is clogged…

the Gami spread will usually point it out…

lean slowly while approaching peak…

if things misbehave early on… there is something wrong feeding that cylinder…

probably not a cylinder issue.  For that we have small cameras… pics of valves and cylinder walls are cool!

PP thoughts only, not a mechanic…

best regards,

-a-

[carusoam]

Roughly speaking…

max FF is about 2X cruise FF…

if your io360 is cruising using 10gph, it’s full rich max FF will be near 20gph…

same for the io550… 15 and 30 gph

anyone with a Missile using 2700 rpm… can easily benefit from moving the FF towards a higher number.

the ovation uses 2500 rpm and 25 gph (?)

the Standing O uses 2700 rpm and enjoys 30 gph…

the excess FF goes directly to cooling EGTs and CHTs 

excess FF to a cylinder can affect the A/F ratio too much.. causing misses and washing the oil of the cylinder walls….

we are supposed to follow official documentation for setting FF.  But, sometimes the documentation is in error, or not updated…

check with your mechanic on how to handle increasing FF…

PP thoughts only, not a mechanic…

[PT20J]

An intake leak significant enough to affect cruise should result in a really rough idle.

Full power fuel flow of 18+ gph at sea level seems about right. My IO-360-A3B6 flows that on takeoff.

Before tearing into the engine, I'd check all the connections to the #3 CHT probe wiring and swap the CHT connections to another channel on the engine monitor. It might be an issue with the monitor rather than the probe.