M20K Fuel Flow Issue on Cylinder 1

[dtoelke]

Hi all,

After several busy weeks I was finally able to fly last week and run a GAMI spread to diagnose the overheating issue of cylinder 1 on takeoff/climb.  Not a massive overheating mind you (~390-400 deg) but still much higher than normal.  Below are the screenshots from May this year (poor data rate but it gets the point across) and the one I took last week.  You can see that the May spread was very good (about 0.2 gph).  The one from last week however shows the cylinder 1 peak occurring roughly 1 gph higher than the rest of the cylinders; the other cylinders all look the same as before.  To me this indicates a partial fuel blockage in either the injector itself or the feed line/distributor.  I removed the injector before the flight (since I suspected this might be the issue) and everything looked clean and free.  Reinstalled and flew the plane.  Do y'all agree with my diagnosis?  What other parts are susceptible to plugging?  Since it's only this cylinder and total flow rates are normal on takeoff and cruise, I'd think it would be something downstream of (or in) the fuel distributor/spider.  Should I send the injector back to GAMI to get it flow tested first before I do anything else?

-Don

 

[carusoam]

It is a normal procedure to take your data to your mechanic and expect him to recommend cleaning that injector.

if he has real talent, he catches the speck of dirt for further analysis.

the follow up exercise involves pulling all the injectors and performing a flow rate test on all of them.  Essentially running fuel through the injectors into jars for a set period of time.  Measure the fuel in each jar.

see which cylinder stands out.

for the record, I am only a PP, but I have read a lot of MS threads...

 

best regards,

 

-a-

[Guest]

A leaking induction pipe at could also cause a higher EGT.  Connect the blow side of a new clean shop vacuum to the compressor inlet of the turbocharger and turn it on, then spray a soap and water mixture on all of the joints in the induction system, as well as the upper deck air system.  While you're at it hook it to the tail pipe for the same test.

Clarence

[Shadrach]

It is a normal procedure to take your data to your mechanic and expect him to recommend cleaning that injector.

if he has real talent, he catches the speck of dirt for further analysis.

the follow up exercise involves pulling all the injectors and performing a flow rate test on all of them.  Essentially running fuel through the injectors into jars for a set period of time.  Measure the fuel in each jar.

see which cylinder stands out.

for the record, I am only a PP, but I have read a lot of MS threads...

 

best regards,

 

-a-

This would be one method used with an engine with stock injectors. The thing about GAMIs is that they are tuned to the airflow that goes into each cylinder (pretty even) and all of the fuel that migrates from the injectors up stream.  I believe #1 is the rear cylinder on the passenger side. The injector should produce slightly less than the one in front of it (#3) and even less than the one in front of that (#5).  I would think it would be hard for any one other than GAMI to flow test their injectors.

Edited September 9, 2015 by Shadrach

[Shadrach]

A leaking induction pipe at could also cause a higher EGT.  Connect the blow side of a new clean shop vacuum to the compressor inlet of the turbocharger and turn it on, then spray a soap and water mixture on all of the joints in the induction system, as well as the upper deck air system.  While you're at it hook it to the tail pipe for the same test.

Clarence

Clarence,

Can you give me a quick explanation as to why this happens on a blown engine? I get that an induction leak on an NA engine means unmetered air is entering the combustion chamber thereby creating a leaner mixturer. It would seem that with a turbo you would have metered air leaking, thereby making the mixture richer. Clearly I'm misunderstanding something.

Edited September 9, 2015 by Shadrach

[DonMuncy]

A few years ago, I was on my way to Kerrville when my engine went slightly rough. After a little "in the air" diagnosis and determining it was likely not a imminent danger problem, I continued and landed at Kerrville. I told the folks at Dugosh that I suspected my #x fuel injector was clogged. They pulled the injector and found a speck of debris. After cleaning the injector and reinstalling the injector, they test ran the engine and everything looked fine.

I was pleased they only did the work necessary to solve the problem, charged me a half hour, and sent me on my way. I did not (and do not) consider a debris clogged injector, with no other indication of a problem, to be an indication of a systemic malfunction requiring a more thorough testing of the fuel delivery system.  

[dtoelke]

A leaking induction pipe at could also cause a higher EGT.  Connect the blow side of a new clean shop vacuum to the compressor inlet of the turbocharger and turn it on, then spray a soap and water mixture on all of the joints in the induction system, as well as the upper deck air system.  While you're at it hook it to the tail pipe for the same test.

Clarence

Clarence,

Can you give me a quick explanation as to why this happens on a blown engine? I get that an induction leak on an NA engine means unmetered air is entering the combustion chambe thereby creating a leaner mixturer. It would seem that with a turbo you would have metered air leaking thereby making the mixture richer. Clearly I'm misunderstanding something.

Shadrach you are correct.

Clarence, that would be the case on an N/A engine, but would really only occur at low cruise power/low altitude for the K (when the MP is lower than the ambient).  If it was an induction leak here, two things would happen:

1) On takeoff/climb, the cylinder would run richer and cooler since the manifold pressure is HIGHER (36") than ambient (~29").  In my case it's running leaner.

2) During cruise at 4500 as tested at 65% power, the mixture wouldn't be significantly affected since the manifold pressure would be roughly the same as ambient (+/- 2" depending on day).  Again it's also running leaner.

From this information I am 99% certain that the problem is fuel flow through the #1 injector, #1 line, or something in the fuel distributor (spider).  I'm just wondering how best to approach the diagnosis.  I could send the injector back to GAMI for testing but if there's a method to test the other components first I'd think that would be better.

[Guest]

I've seen cracked, ruptured and various leaking induction pipe cause all manner of interesting engine problems, its only my suggestion based on my experiences.  As I'm not there to look at your engine, it all I can offer you, but it appears from your post you've got it figured out, so why post the question?

 

"From this information I am 99% certain that the problem is fuel flow through the #1 injector, #1 line, or something in the fuel distributor (spider).  I'm just wondering how best to approach the diagnosis.  I could send the injector back to GAMI for testing but if there's a method to test the other components first I'd think that would be better."

Clarence 

[dtoelke]

I've seen cracked, ruptured and various leaking induction pipe cause all manner of interesting engine problems, its only my suggestion based on my experiences.  As I'm not there to look at your engine, it all I can offer you, but it appears from your post you've got it figured out, so why post the question?

 

"From this information I am 99% certain that the problem is fuel flow through the #1 injector, #1 line, or something in the fuel distributor (spider).  I'm just wondering how best to approach the diagnosis.  I could send the injector back to GAMI for testing but if there's a method to test the other components first I'd think that would be better."

Clarence 

Sorry Clarence I did not mean to discount your input.  I think I just worded the original question poorly. What I'm really interested in is finding out if there are any other potential plugging points I haven't listed that would affect only one of the injectors and also in what order I should troubleshoot.  Do I send the injector in to be flow tested, open up the fuel distributor, etc?