Mixture too lean; misfires; 0.7 GAMI spread

[jaylw314]

1 hour ago, carusoam said:

I updated the close ups...

One mag is doing something differently than the other...

Anyone agree / disagree?

FWIW, this is from MB's article at SavvyAnalysis (emphasis added)

"If your ignition system is healthy, when you switch to single-magneto operation you should see all EGT bars rise by 50°F to 100°F. They may not all rise the same amount; in fact, it's perfectly normal to see even-numbered cylinders rise more than odd-numbered ones (or vice-versa). What's important is that all EGT bars rise, and that all remain fairly stable at their elevated values. You will feel a small but perceptible loss of power during single-mag operation, but the engine should continue to run smoothly without uncomfortable roughness. (The engine will always run slightly less smooth on one magneto than on two, but roughness sufficient to get your non-pilot passengers to ask "what's wrong with the engine" is definitely too much!)"

It doesn't mean there's nothing wrong, but the even-odd difference during the mag checks might not mean anything... 

[chrixxer]

27 minutes ago, bradp said:

I am wondering whether we’re taking about both a fuel and spark issue   

 

And just to confirm did the spider and lines ever get either replaced or thoroughly inspected?  I’m trying to work out conceptually whether high fuel pressure after the servo was replaced could was associated with high or low flow. If the servo was replaced or metering was down-adjusted because of a downstream obstruction/ foreign body you’d end up potentially normalizing the pressure and decreasing the flow too much. Tells me I need to study Bendix failure modes a bit better :-).   My overall question is if a piece of something landed in the wet part of the fuel servo where else did it go?

Baby bottle test will be useful.  Do them with nozzles on and off.  Make sure no kinks or cracks in lines while you’re there. 

make sure that the spider was opened and inspected.  

If you want to test flow through lines you can remove individually and test their flow rate roughly by attaching to a flask / funnel / vessel with a known volume of liquid and time how long it takes to flow past  for each line (like you’d do for a paint viscosity test).  

There has been mention of a potential for induction leak in the thread- just do the savvy profile to help rule out  

for a 4-banger lycoming you can swap injectors to get a better gami spread.  

Given your somewhat bad luck don’t touch without a trusted mechanic :-) 

 

Also, once we know the diagnosis this would be a good one for the savvy newsletter 

 

 

Spider was not replaced or, AFAIK, inspected. Lines were not replaced but were inspected. High fuel pressure was the "fault" of the fuel pump (even after the servo came back bench-adjusted, PSI was still over the red line, until we swapped in a different pump). The piece of gasket was retrieved intact, and I believe it was taken out of the "dry" side of things; FWIW, I was able to restart the engine in flight by leaning almost to ICO, which brought the fuel-air mixture back to one where combustion could occur - which heavily implies an airflow blockage, not a fuel blockage.

Paul at Savvy (this morning) stated there was no evidence for an induction leak and said there was no need to run that flight profile, but as I'd already done it, we have the data just in case.

I'm not even doing my own oil changes until I've done one with an A&P watching me do it! (Thinking oil every 35 hours by myself, oil + filter every other oil change with an A&P. $300 for an oil change every 35 hours is a bit on the steep side...)

[carusoam]

 

background read for mag checks...  AOPA. (Nothing stands out here)

https://www.aopa.org/news-and-media/all-news/2002/january/flight-training-magazine/the-magneto-check

[carusoam]

Lycoming IO360 operator manual pic...

Cylinder numbers mag locations and top/bottom wire locations...  (in the event you go looking at plugs...)

 

[chrixxer]

Okay, I got Savvy's three page analysis of my recent diagnostic flight (I flew each of these flight profiles). Take-aways:

• My plane has lupus.
• Induction test shows a possible leak around #3, possibly impacting #2 and #4 as well.
• Multiple GAMI sweeps confirm non-optimal mixture distribution (0.5, 0.9, 0.7 GAMI spreads). Injectors 1 & 4 are equally lean "making it unlikely they are both dirty," and 2 varying rich injectors, "suggesting cleaning is unlikely to help." After checking for an induction leak, will try cleaning, and/or swapping 1&4 and 2&3.
• Premature ignition misfire bottom 2 & 4, top 4 plugs. The bottom plugs are ~6 months and 80 hours old Champion REM37BYs; if internal resistance is off (>5K ohms), will replace with Tempest REM37BYs. First we'll be cleaning and inspecting them.
• Mags are closely timed, timing "appears even."
• RPMs are low (2629 on take-off, not rising to 2641 until 11 minutes into climb, when I leveled off). Will have prop governor adjusted.
• Max power FF 15.7 gph. When everything else is dialed in, will address this.
• I might have a probe failing on CHT1 ("suspected non-standard"); I've recently had to replace CHT3, factory CHT, and EGT4, and most of the JPI probes are the same age.
• Master bus is good with constant 0.3V oscillations. No inoperative sensors, anomalous channels, or noisy channels.
• My powerplant management is "ok."
• Engine monitor data is good.
• CHTs are excellent in climb (318-360).

The saga continues. (So glad my Labrador's chemo is almost done, I can only hemorrhage money from so many places at once...)

Edited May 24, 2019 by chrixxer

[gsxrpilot]

29 minutes ago, chrixxer said:

Okay, I got Savvy's three page analysis of my recent diagnostic flight (I flew each of these flight profiles). Take-aways:

• My plane has lupus.

Ok, that's funny. I know it's not easy to laugh in this situation, but good onya for that.

I think an important point that everyone should think about is that entire bulleted list is derived from a data logging engine monitor. Without one, it would likely take many hours of A&P services to troubleshoot. As you've already had done, to minimal effect. I know everyone knows me around here for this one soapbox, but I can't imagine why anyone would own an airplane without a good engine monitor.

[chrixxer]

8 minutes ago, gsxrpilot said:

Ok, that's funny. I know it's not easy to laugh in this situation, but good onya for that.

I think an important point that everyone should think about is that entire bulleted list is derived from a data logging engine monitor. Without one, it would likely take many hours of A&P services to troubleshoot. As you've already had done, to minimal effect. I know everyone knows me around here for this one soapbox, but I can't imagine why anyone would own an airplane without a good engine monitor.

Right? And that's assuming you knew the issues were there to look for them in the first place. I flew my boss up to Santa Monica today to ferry his 340 down to Torrance, he was giving me grief for flying special flight rules (which requires a descent from 4,500' to 200' in a relatively short amount of time and tight space, and even then I'm often slipping for a mile or three to make the field), vs. staying below the LAX Bravo shelf and flying up the LA River. That means staying below 2,000' up the river (as seen in the race sequence in Grease), and below 2,500' around downtown Los Angeles. Zero options if the spinny part stops doing its thing. I'm like, "I don't have a twin, or a 'chute." "With an engine running as great as yours is..." he replies, drawing on his 5,000 hours of experience (1,000 of them in an M20J), ATP credential, etc.

It runs smooth. It idles smooth, it climbs great (at ~110 mph IAS and the two of us, and 30 gallons of fuel, we were climbing at ~800 fpm above 2,000', on a warm day). It just sort of purrs. If you weren't obsessing over the JPI data, you'd likely never know anything was amiss, until it had developed into a much larger, much more urgent (probably) problem.

 

[Guitarmaster]

Okay, I got Savvy's three page analysis of my recent diagnostic flight (I flew each of these flight profiles). Take-aways:

• My plane has lupus.
  

I literally laughed out loud at this...


Sent from my Pixel 2 XL using Tapatalk

[ArtVandelay]

I thought if the mag checks results in different EGT peak temperatures , it was because of timing differences?



Tom

[carusoam]

If one peak is taller than the other peak... The Timing is suspect...

the plugs that fire off earlier, will have the fuel burn more complete, so the EGTs won’t be as hot...

 

In this case the two humps in the inflight mag test were similar in shape overall... four plugs look very consistent.  The other plugs are asking to be checked/tested... mostly because the L and R mags on the same cylinder are showing a difference...

Since Champion plugs are known to fail slowly, from day 1, they are easy to test... 

Mags are always suspect as they wear at a pretty quick pace... 500hrs makes sense for performing their service... some have capacitors and plastic gears that don’t always age very well... the mag generates a lot of ozone, and O3 promotes oxidation quite readily... including oxidation of the plastic gear... it turns brownish as if it baked...

PP thoughts only...

Best regards,

-a-

[jaylw314]

2 hours ago, ArtVandelay said:

I thought if the mag checks results in different EGT peak temperatures , it was because of timing differences?
 

This weeks SavvyAnalysis e-mail newsletter had a MB article that addressed this.  Unfortunately, I just deleted the e-mail.  He mentioned that a change in the overall increase in EGT between the two mag checks suggests the two mags are timed differently.  However, he also pointed out it is not unusual to see the even cylinders have a larger climb than the odd cylinders on one mag or vice versa.  He said when the bottom (or top, I can't remember for sure) spark plugs fires during a mag check it results in a higher EGT increase.

So looking at the EGT traces, yes the evens have a larger increase on one mag, and the odds have larger increase on the other, but both mags produce a similar overall EGT increase, suggesting they are timed the same.

Can someone else confirm my memory of this is correct (or not, as is more likely)?

[carusoam]

See if this can explain why...  (it might not)

Expect the top plugs to remain cleaner...

• Clean plugs initiate a better burn, compared to oil soaked, lead balled, or dirty plugs...
• completing the burn sooner leaves less fuel to burn in the exhaust...
• less fuel burning in the exhaust is the cooler EGT...

There is a picture posted above showing which mag fires the top plugs on one side, and the bottom plugs on the other...

Mike Bush really makes sense out of this really cool data...

Of course... this requires the A/F ratios to be perfectly even, getting to the cylinder and the valves all working equally well...

Interesting stuff...

MB is a practical genius with a passion for aviation engines...

Best regards,

-a-

 

[carusoam]

Let’s take Art/Tom’s point of view for a moment...

He is looking at the lesser stressful ground run-up...

1) If we look at the top line EGTs... of both the L and R peaks... one is visually taller than the other making it look like timing is indeed different... purple and gold... the R peak is lower than the L Peak... (remember this, something flips)

2) This makes us look at the next mag check, to confirm if we are seeing the same thing there as well...

3) the inflight mag check doesn’t seem to have that variation anymore... (may not eliminate a mag issue, just less probable...)

4) Back to the ground run-up...the top lines are different, but take a look at the bottom two lines... red and brown...  they are different in the opposite way...

the bottom two lines have a short peak on L, and a taller peak on R...

5) Anyone with a really strong memory can review which plug matches which mag, is that top or bottom.... I would have to write out abig chart...

6) High EGTs indicate a plug not working perfectly...   too bad..., cause they graph very nicely...

7) Match the high temps with the expected high resistance plugs....

8) Match the lower temps with the expected clean burning plugs... or plugs working so poorly raw fuel is not being burned...  this might be possible with the ground run-up... in flight, the raw fuel is definitely getting burned...

9) if the plugs are so high resistance they impede/delay the fuel burn they become pretty obvious in the JPI raw data graphs of the EGTs...

10) What makes the Red line fall out the bottom?  Is that real... or a probe location issue?

11) What makes the purple line stand above the rest? Real, or probe?

 

12) Fuel injectors have a way of  making things colder... more fuel, colder EGTs.  (ROP)

13) Some of these could be FI related... is the Red line running cold because the FF to that FI is higher than the rest?  The baby jar flow test would be interesting for this...

14) The purple line, the hot one, is probably the opposite... the baby jar test probably may indicate its FF to the FI is running less, causing higher EGTs.

15) Air leaks... very similar to FF to the FI... any extra air getting to one cylinder will appear hotter on the EGT...

16) if all the FI baby jar test show identical flow, and one EGT is extra hot... it is possible that extra air is leaking in upstream... intake tube seals, sniffle valve, something else....

 

If you could do this yourself...   You would want to know...

1) a pic of all 8 plugs...

2) resistance measurements of all eight plugs... expect one or two to fall off the ohm cliff...

3) Baby jar FF test, the identical jars are a nice visual test... find a way to weigh, or measure the volume of the liquid for comparison... be as accurate as possible... with the FIs is most important... but, if there is a problem upstream, without the FIs will be very telling...

4) expect one to be flowing more than the other three... and one to be flowing less...note which cylinder these come from before accidentally losing track...

 

That’s a lot of work... but you will have a great baseline for any performance issues that come up next...

 

Anyone reading get this far?  

PP thoughts only, not a mechanic, I may have done some reading somewhere... most likely, MS...

Best regards,

-a-

[chrixxer]

Not sure why we're still talking about timing (@carusoam)? I've pointed out repeatedly, the mags were redone 6 months / 100 hours ago by Aero Accessories, and the Savvy report confirms they're timed tight. It's not a mag issue. It's a plug issue.

As to the probes, IDK. EGT4 and CHT3 were replaced very recently, the rest are pretty old. Savvy was asking if the factory probe was CHT1 as it's reading differently than the other probes - suspect it's just old.

 

[carusoam]

Chrix,

That was a response to Art/Tom...  Timing looks good to me.  Tom had pointed out some interesting artifacts...

This part is solely me trying to visualize what to look for if one were to chase plug resistance, and possible fuel flow issues using the baby jar test...  it uses the cylinder drawings above to get the names of things...

 

Chart... use color coding to match the JPI chart...

C1

Top Plug (Lmag) ohms

Bot Plug (Rmag) ohms

FI1 Timed FF in ml

 

C2

Top Plug (Rmag) ohms

Bot Plug (Lmag) ohms

FI2 Timed FF in ml

 

C3

Top Plug (Lmag) ohms

Bot Plug (Rmag) ohms

FI3 Timed FF in ml

 

C4

Top Plug (Rmag) ohms

Bot Plug (Lmag) ohms

FI4 Timed FF in ml

 

Odd (copilot side) cylinders are powered by the L mag on top plugs, R mag on bottom

Even (pilot side) cylinders are powered by the R mag on top plugs, L mag on bottom

 

To be clear... I made this chart to try to visualize the data collection challenges... it can be off in several different ways...

 

PP thoughts only, trying to be helpful, I may have missed the target...

Best regards,

 -a-

[carusoam]

When it comes to the JPI probes...

It is good to know where the ship’s gauge is... and which probe is feeding it... and which location it is using...

The JPI EGT probes could be all the same... but one is likely to be a bit quirky, if the ship’s gauge is occupying the same standard spot as the other cylinders... an additional hole has been drilled to mount two gauges in one pipe...

Similar challenge with the CHT probes... the ship’s CHT is usually occupying the one CHT well available on each cylinder... so the JPI gets the additional TC either piggybacked with the CHT well (best, but different) or a TC/sparkplug seal  (not very good, and worse data)

Some Mooneys use a thermistor for the ship’s CHT gauge...  extra detail...

 

A quick test for how well TCs are reading... they should all be reading very similar numbers  after a day in the hangar...

Over the years some JPIs have been miswired... this test usually indicates when something is miswired using improper TC wires...

 

PP thoughts only, Best regards,

-a-

 

[chrixxer]

1 hour ago, carusoam said:

When it comes to the JPI probes...

It is good to know where the ship’s gauge is... and which probe is feeding it... and which location it is using...

The JPI EGT probes could be all the same... but one is likely to be a bit quirky, if the ship’s gauge is occupying the same standard spot as the other cylinders... an additional hole has been drilled to mount two gauges in one pipe...

Similar challenge with the CHT probes... the ship’s CHT is usually occupying the one CHT well available on each cylinder... so the JPI gets the additional TC either piggybacked with the CHT well (best, but different) or a TC/sparkplug seal  (not very good, and worse data)

Some Mooneys use a thermistor for the ship’s CHT gauge...  extra detail...

 

A quick test for how well TCs are reading... they should all be reading very similar numbers  after a day in the hangar...

Over the years some JPIs have been miswired... this test usually indicates when something is miswired using improper TC wires...

 

PP thoughts only, Best regards,

-a-

 

Factory CHT is in 3, and the JPI piggy backs it. There's no factory EGT in a '69 F. I can't find my notes at the moment, but when I went to adjust the OAT reading I noted the EGTs and CHTs and they were within 2-3 degrees, "room temperature."

 

[chrixxer]

Update. Leakdown looks okay(ish), 78/72/79/78 over 80 (cylinders 1-4 respectively), performed cold. A&P says probably nothing to worry about vis-a-vis #2 (which is also the cylinder I was getting occasional oil fouling of the bottom plug in, before I swapped the bottoms from fine wire to "REM37BY style" plugs (previous A&P had a habit of interpreting my instructions more liberally than I generally like...).

Injectors: 40/38/38/37cc (1-4 respectively).

Mag timing is spot on.

Top plugs were all weak. (Champions. Swapping all to Tempest.)

Can't adjust the prop governor without removing it, a relatively big job (have to remove the right mag and oil filter). I'm off by about 50 rpm (seeing 2640-2650 on take-off at sea level). Live with it for now? 

[jaylw314]

2 minutes ago, chrixxer said:

 

Can't adjust the prop governor without removing it, a relatively big job (have to remove the right mag and oil filter). I'm off by about 50 rpm (seeing 2640-2650 on take-off at sea level). Live with it for now? 

The governor has to come off for speed adjustments?

[chrixxer]

8 minutes ago, jaylw314 said:

The governor has to come off for speed adjustments?

According to my A&P, yep: “Can’t adjust the prop gov without removing. They put the adjuster screw in the worst place.”

 

[carusoam]

What gov do you have?

Many have gone to a new / modern gov compared to the older original version...

See if this is right...

http://www.pcu5000.com/

My O360 had its gov removed to replace some worn parts... not a big deal for that...

Best regards,

-a-

[chrixxer]

Meh. Now it sounds like these quibbles are the least of my issues:

“Initial measurement is showing .480” + on the exhaust lobes and only .250” avg on the intakes. I had an engine builder here earlier and he’s confident the lobes are worn bad. Also your lifters are collapsing and they shouldn’t be. Probably from age. That’s why I have to remove part of the valve train to get an accurate measurement. Sorry for the bad news.”

(I had about $25K put away towards a panel upgrade or an engine overhaul (1800 SMOH, done in 1991 by Firewall Forward), but then my Labrador was diagnosed with lymphoma and the chemo bills started coming in... She might be parked for a few months. )

[Guest]

3 hours ago, chrixxer said:

According to my A&P, yep: “Can’t adjust the prop gov without removing. They put the adjuster screw in the worst place.”

 

The stop screw can be in a challenging location, but not impossible and certainly doesn’t require removing the governor or any other parts.  

Clarence

[chrixxer]

Well, all of this is moot. The valve lift check was devastating; the cam has very worn lobes:

Initial measurement is showing .480” + on the exhaust lobes and only .250” avg on the intakes. I had an engine builder here earlier and he’s confident the lobes are worn bad. Also your lifters are collapsing and they shouldn’t be. Probably from age. That’s why I have to remove part of the valve train to get an accurate measurement. Sorry for the bad news.

Later:

Bad news. About half of your front intake lobe is gone. The two engine shops I spoke with said the cam is toast. Intake lobe is at .167”. Exhaust is .335”. They’re supposed to be the same.

I had a liquid reserve fund, but... (You know how I said I was glad my Labrador's chemo was almost done, on May 24th? On May 25th he developed hemorrhagic cystitis (side effect of the Cytoxan), which required lots of treatments and ultrasounds etc., and one of those ultrasounds revealed he was failing the CHOP protocol. July 2nd we started him on a rescue protocol and he got another DMSO infusion for the cystitis. July 3rd he died. August 17th I brought home (in the dying Mooney) an 8 week old Labrador puppy. So, yeah, I don't have that reserve right now. Flying was nice while it lasted! I'll get it back up, just need to figure out how, first.

What am I looking at, $30,000? (So much for the G3X...)

[Guest]

16 minutes ago, chrixxer said:

Well, all of this is moot. The valve lift check was devastating; the cam has very worn lobes:

Initial measurement is showing .480” + on the exhaust lobes and only .250” avg on the intakes. I had an engine builder here earlier and he’s confident the lobes are worn bad. Also your lifters are collapsing and they shouldn’t be. Probably from age. That’s why I have to remove part of the valve train to get an accurate measurement. Sorry for the bad news.

Later:

Bad news. About half of your front intake lobe is gone. The two engine shops I spoke with said the cam is toast. Intake lobe is at .167”. Exhaust is .335”. They’re supposed to be the same.

I had a liquid reserve fund, but... (You know how I said I was glad my Labrador's chemo was almost done, on May 24th? On May 25th he developed hemorrhagic cystitis (side effect of the Cytoxan), which required lots of treatments and ultrasounds etc., and one of those ultrasounds revealed he was failing the CHOP protocol. July 2nd we started him on a rescue protocol and he got another DMSO infusion for the cystitis. July 3rd he died. August 17th I brought home (in the dying Mooney) an 8 week old Labrador puppy. So, yeah, I don't have that reserve right now. Flying was nice while it lasted! I'll get it back up, just need to figure out how, first.

What am I looking at, $30,000? (So much for the G3X...)

That really sad news.  I can’t imagine losing my dog, my sympathies.

Clarence