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New Owner of a M20E


DustinNwind

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Hi All! I'm the new owner of a 65' M20E. Really excited to join the Mooney family after looking for the right bird for the last 6 months. 

 

Any time you get a new machine it goes through some issues - Here's mine maybe someone can help out:

The plane has a new engine from Western Skyways around 15 hours now. The #3 cylinder is running extremely hot on climb out (475) and during level flight 415 - this is all according to a JPI 700. The rest of the cylinders are normal. Oddly the original CHT is showing very low temps. We checked injector flow and it's flowing correct. The mechanic says that the probe is faulty. Attached is a photo (left cylinder is #3) after 5 take offs hitting the 450+ and 415 for 3 hour cross country, of course all according to JPI 700 - wouldn't you think the engine would be a different color if it was actually running that hot? Any help on this would be greatly appreciated! 5763QatLASAR.thumb.jpg.1c00384c2cd4951f6b10157408e48538.jpgIMG_3749.thumb.JPG.e37d32485b22e42614af9d1569ab63e5.JPG

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#3 seems to be the cylinder Mooney usually (always?) uses as the one for the primary CHT gauge.  As such, when the EDM 700 is installed, you can't use the same JPI temp probe that is used on the other cylinders--many old installations use a spark plug gasket temp probe that is much less accurate because of its placement, and can be off by +/- 50 oF. 

That being said, your numbers are still way too high.   If you have the spark plug gasket probe, you can't swap it for another probe.  If your A&P thinks the probe is off, you could replace it with a newer JPI probe ($150 or something) that sits like a washer under the factory bayonet probe.  Still not perfect, but significantly better.

Someone in a previous thread also mentioned dunking the probe in boiling water to test its accuracy, although that obviously doesn't go very high.

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34 minutes ago, DustinNwind said:

The #3 cylinder is running extremely hot on climb out (475) and during level flight 415 - this is all according to a JPI 700.

Yes, this is very bad.

If you pull throttle back to slow flight does the temp go down? Could be an airflow issue.

Whatever, if these are the actual temps that cylinder will go. You can't run it that high.

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2 minutes ago, HRM said:

Yes, this is very bad.

If you pull throttle back to slow flight does the temp go down? Could be an airflow issue.

Whatever, if these are the actual temps that cylinder will go. You can't run it that high.

I know it’s bad if these are the actual temps, the question is has anyone experencied this on a JPI 700 for the #3 cylinder. 

 

If you pull the the throttle back all cylinders get cooler so that’s not direct help to figure out the #3 cylinder issue. 

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4 minutes ago, DustinNwind said:

I know it’s bad if these are the actual temps, the question is has anyone experencied this on a JPI 700 for the #3 cylinder. 

If you pull the the throttle back all cylinders get cooler so that’s not direct help to figure out the #3 cylinder issue. 

Unlikely to be a JPI700 issue if you have swapped sensors. My solution would be an EI MVP-50 (what I have) :P

That said, you said "but it might not be a JPI 700 probe" which could be the exact source of the problem. Nevertheless, running that cylinder over 400º will kill it.

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The voltage used in thermocouples is very very low.  The voltages in spark plug cables is very very high.   I would not run the thermocouple cables along with the spark plug cables.  See how the factory did not do that.  Many here say it is fine to route them together.

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That temperature is more like what some C model owners report.

As has been pointed out, routing JPI wires with ignition wires is not correct.  That being said, both number 1&3 are the same way so both could be expected to be high?

What version of probe is installed in cylinder 3, washer style or adapter probe?

I would simply install another JPI probe or switch with one from another cylinder which is reading correctly.  

Clarence

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It looks like you have the spark plug washer style probe on cyl 3. Is that the probe you swapped or did you move the factory probe?  I would remove the spark plug and put the sensor in boiling water just to make sure it is working and wired correctly. 

Also congrats on the new plane, looks like a beauty. 

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Summary...

1) Check where all five CHT probes are. 4 for the JPI and one for the ship’s gauge.

2) By regulation the ship’s gauge is occupying a spot that some owners prefer to put a JPI probe...

3) JPI supplies some secondary sensors to piggyback the CHT well that the ship’s gauge occupies...

4) know what you have and where it is residing... 

5) piggyback gauges are typically near the CHT well, but not the same as being in the well...

6) sparkplug seal sensor types are in an extra hot position...

7) in the pic there are two EGTs in one exhaust header... one further down the tube than the other...  this variation is OK for finding peak EGT, but terrible for finding the actual EGT. For best results all EGTs should be the same distance from the exhaust valve...  

8) just make sure you know where your JPI probes are to best understand why they are reporting what info you are getting...

9) The regulations require where the ship’s CHT sensor is placed so that the redline on the gauge reads properly...

10) almost forgot...  the signals for thermocouples are in microvolts, so their routing is sensitive to things that have megavolts inside them...

11) When DonMuncy said swap a probe, there may have been some confusion... literally, swap two probes from two neighboring cylinders... TEMPORARILY... to see if it is a probe error.  Does the funny temperature move with the probe?  Or does the other probe read the same funny temperature  in the same cylinder...

Let is know what you find...

PP thoughts only, not a mechanic, all stuff I learned reading MS...

Best regards,

-a-

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Couple of thoughts. You could still move the spark plug probe from #3 to #1 and see how it reads.  Under those conditions, they should be within a few degrees of each other.  You could also have and exhaust gasket leak at #3, blowing on the probe under the plug.  You would usually see some white deposits, but it may take a few flights to become visible.  On occasion, the exhaust will not line up.  Torque will pull it in, but not completely flush.  I had an exhaust that turned out to be bad from overhaul causing continuous leaks.

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There's a fair amount of troubleshooting that can be done on the ground without running the engine as per the posts in this thread. I'd be very hesitant to fly until I knew a lot more. I'm sure you paid for that E, an amount commensurate with a fresh engine. I would want to protect that investment...

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I had the same exact issue possibly.  My number three probe was attached to the top spark plug.  #3 always ran 50 degrees or so hotter than the rest.  We simply pulled the factory probe and put a JPI prob in the hole for "testing purposes."  After determining it was a prob issue I bought a probe that piggybacks off of the factory probe.  The piggyback probe led to a lower reading than the others.  Long story short, a couple of years later I have a JPI900 with all the old factory stuff removed and temps read fairly close on all cylinders.  The weak link for me was how the JPI doesn't work effectively with the spark plug probe or the factory piggyback probe, only through the mounting like the other three.

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Thanks everyone for their feedback on the issue as it has helped me move along. I talked to JPI today and they said with the CHT probe on the spark plug that 50 degrees warmer is normal. That makes no sense to me to have a wrong number be "normal". Kinda pissed me off that they are saying that's acceptable.. 

 

I used RVT and plugged the holes in the baffling - and still the same issue. Tomorrow my mechanic and I will be piggyback the original ships CHT probe and see how that goes. Attached are the photos of how it looks now. Again, thanks everyone for your comments and I'll let you know my findings. 

 

Regards, DIMG_3757.thumb.JPG.9cff9dba9701c4f0b508a3dc984520e3.JPGIMG_3760.thumb.JPG.5bca98f8b28c6cefa991f65cb947eef1.JPG

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4 minutes ago, DustinNwind said:

Thanks everyone for their feedback on the issue as it has helped me move along. I talked to JPI today and they said with the CHT probe on the spark plug that 50 degrees warmer is normal. That makes no sense to me to have a wrong number be "normal". Kinda pissed me off that they are saying that's acceptable.. 

 

I used RVT and plugged the holes in the baffling - and still the same issue. Tomorrow my mechanic and I will be piggyback the original ships CHT probe and see how that goes. Attached are the photos of how it looks now. Again, thanks everyone for your comments and I'll let you know my findings. 

 

Regards, D

Yup, that's a spark plug gasket probe.  They are inaccurate because the spark plug is the hottest part of the cylinder, but the top spark plug also gets exposed to the most cool air.  Hence, depending on the vagaries of installation, it can be +/- 50 oF

If we were convinced it was a measurement error, you could move the probe to the TOP spark plug, but that still doesn't solve our problem as to what the real #3 cylinder temp is.

Like I said before, the piggyback sensor should be more accurate, although still not perfect.

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When I’m concerned about high temps, I track my JPI on Cylinder 3 and then lean over to the analogue needle to verify the real temp of Cyl 3 when JPI 3 is over 400.

It’s not eloquent or pretty. I do find some peace of mind when I download and graph the data. There is a lot to be said for consistently.

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2 hours ago, DustinNwind said:

Thanks everyone for their feedback on the issue as it has helped me move along. I talked to JPI today and they said with the CHT probe on the spark plug that 50 degrees warmer is normal. That makes no sense to me to have a wrong number be "normal". Kinda pissed me off that they are saying that's acceptable.. 

 

I used RVT and plugged the holes in the baffling - and still the same issue. Tomorrow my mechanic and I will be piggyback the original ships CHT probe and see how that goes. Attached are the photos of how it looks now. Again, thanks everyone for your comments and I'll let you know my findings. 

 

Regards, DIMG_3757.thumb.JPG.9cff9dba9701c4f0b508a3dc984520e3.JPGIMG_3760.thumb.JPG.5bca98f8b28c6cefa991f65cb947eef1.JPG

Your EGT probe is missing the gasket.  A thin curved stainless disc about the diameter of a quarter.  An adapter probe or a 3/8” washer probe under the existing CHT probe should help, however if you want to know the real number, remove the OEM probe and adapter temporarily and install a bayonet JPI probe fr a few flights.

Clarence

Clarence

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Hi Folks, 

Thanks everyone for the help, we have figured out the problem. The issue as others have mentioned is the JPI probe on #3 goes to the spark plug to get its reading which causes ~50 degrees warmer. We confirmed this by putting the #3 probe on #1 spark plug and reading the JPI instrument. As we predicted it was going to be ~40 degrees warmer (10 degrees cooler than when on #3 due to being in the front with a little more air). As others have mentioned also, you can piggy back JPI #3 probe to the ships original CHT. Well the problem on my engine is that who ever put the new probe into the engine twisted the probe threading and we can't remove it with out having to possibly tap it to get it back in with a 50/50 change of ruining the cylinder. Engine only has 25 hours so it's tough to justify this ruining a cylinder.

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Dustin,

you seem to be generating a ton of work or stress for yourself....

You seem aggravated by what people have told you...

And now have come to a point that makes less sense... ruining a cylinder over a thermocouple?

Somebody said something was normal, because the way you have things set-up, it is normal... it’s not the best way to do things... but, low cost, legal, and safe? Yes... (that’s why it was done that way...)

Are you working closely with a mechanic?

It helps to have some technical skills to understand why this all works this way...

And Some FAA skills to understand why the plane came equipped this way...

Lots of the work of understanding your plane falls on your shoulders...

When you don’t have these skills, it really helps to have a good mechanic to go to...

Sure, you might be super smart and really good at Astro physics....

But, 60’s plane design and FAA approved modifications don’t come naturally to people, even if they are top level Astro physysists....

1) know what TC belongs where, according to the FAA

2) know what you want for all TCs and where you want to have them

3) have your mechanic make that happen... 

4) might take an hour or two...

5) there is plenty of experience to draw from around here, and from JPI or any other instrument supplier...

Like EGTs... a temperature reading is highly dependent on location.  Moving a few mm away, the temp begins to change...

Instead of precision monitoring of CHTs they are in the close enough mode.   Keep them under 380°F in cruise... a general rule for cylinders in Mooneys... if the reading for one cylinder is off by 25°F all the time, you get used to it quicker than you think.  

I don’t think new planes or new cylinders have made any accommodations for this.  There are plenty of TCs that can fit in one well, but nobody wants to take on the FAA paperwork for that....

Have no fear, you can get this done properly, without the added stress...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

 

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27 minutes ago, carusoam said:

Dustin,

you seem to be generating a ton of work for yourself....

You seem aggravated by what people have told you...

And now have come to a point that makes less sense... ruining a cylinder over a thermocouple?

Somebody said something was normal, because the way you have things set-up, it is normal... it’s not the best way to do things... but, low cost, legal, and safe? Yes... (that’s why it was done that way...)

Are you working closely with a mechanic?

It helps to have some technical skills to understand why this all works this way...

And Some FAA skills to understand why the plane came equipped this way...

Lots of the work of understanding your plane falls on your shoulders...

When you don’t have these skills, it really helps to have a good mechanic to go to...

Sure, you might be super smart and really good at Astro physics....

But, 60’s plane design and FAA approved modifications don’t come naturally to people, even if they are top level Astro physysists....

1) know what TC belongs where, according to the FAA

2) know what you want for all TCs and where you want to have them

3) have your mechanic make that happen... 

4) might take an hour or two...

5) there is plenty of experience to draw from around here, and from JPI or any other instrument supplier...

Have no fear, you can get this done properly, without the added stress...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

 

Carusoam,

All has been done with a mechanic, in fact we had 3 mechanics on the ground and a right seat pilot monitoring the JPI as I flew today to document temps. I appreciate the notion that I should "trust" what people are telling me on a forum is correct but I only accept things that are verified - even more so things need to be verified if I'm getting temps that could cause an engine failure. I verify not only for my pocket book but for the life of my passengers and the my life. So please respect that I'm going to go the extra mile to confirm why something is happening. I don't consider anything I've done extra work, it's just work. Also, I'm so ecstatic there is such a helpful group of folks here willing to tell their knowledge. I'm confused on where you got my aggression towards MS? The only thing I'm aggravated with is who ever rethreaded the probe into this engine muscled it in and torqued it the wrong way so I can't take it out with out having to tap a new hole due to ruining the treads. 

1) All TCs have been identified and that's how we trouble shot today.

2) I want all TCs to work properly as the JPI should be real numbers.

3) I'm not a mechanic nor do I want to be a mechanic, thus I have a mechanic + it's the law.

4) It took 2 for your guidance. 

5) As I said in the first sentence and I'll say it again,  thank you everyone for your words, it has made the trouble shooting easier. Your help is invaluable. As for JPI technical department I will and can not accept their answer "it's normal for the spark plug probe to read roughly 50 degrees warmer than it is. You just have to figure on that in your calculations". I believe in doing something the right way or don't do it at all. Making a probe that reads wrong is not making an accurate piece of equipment.

 

 

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