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Vibration and high EGT from #1


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Last flight out after leveling off for cruise (3500ft) as I was pulling back mixture to lean,  the engine started to vibrate. When going back to near full rich the vibration subsided. The digital EGT showed #1 around 100 to 110 degrees hotter that the other three. Pulled the plugs and they looked good, no oil and normal color as would be expected for proper burn. In looking around here on the board, my search turned up what points mostly to a clogged injector. Will be pulling the injector probably Tuesday and see what I get. In the mean time, was looking for thoughts on this issue. Up to this point the engine has run flawless and smooth for the 40 hours I have owned her! I do not have any type of engine monitor except CHT which was fine, and four position digital EGT. The run up on the ground was a 50 RPM drop left and right MAG.

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Don't go pulling injectors yet. It's entirely possible that this is an ignition issue. Plugs and mags can malfunction across the RPM/power spectrum or in a narrow range.  How high was the #1 EGT?  100degree differential between EGTs is not necessarily abnormal. EGTs are rarely even from cylinder to cylinder.  A plug dropping off at high power will cause an EGT rise and will also result a slower (relatively speaking) combustion event putting one cylinder down on power.   Are you saying that any leaning caused roughness? If not, where did it start? 

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Yea, if there is one clog, there is probably going to be more.   Do the Dixie cup process and toggle the fuel selector valve back and forth while running the fuel pump into Dixie cups.  Debris gets in that valve...   I have made this an annual process   ...  Cost is nothing and easy to do   

Same thing happened to me when I bought mine.. Except at 200agl on takeoff.   I did the above, then decided to send the spider, throttle body, and electric pump for overhaul, sense they were about 18years old .. 

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Don't go pulling injectors yet. It's entirely possible that this is an ignition issue. Plugs and mags can malfunction across the RPM/power spectrum or in a narrow range.  How high was the #1 EGT?  100degree differential between EGTs is not necessarily abnormal. EGTs are rarely even from cylinder to cylinder.  A plug dropping off at high power will cause an EGT rise and will also result a slower (relatively speaking) combustion event putting one cylinder down on power.   Are you saying that any leaning caused roughness? If not, where did it start? 

EGT was about 110 hotter than the rest. I was able to lean a bit before it started to vibrate getting progressively worse the more I leaned. I see the EGT as abnormal as my experience thus far has been no more than 30 degrees between all four until the vib started.


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Yea, if there is one clog, there is probably going to be more.   Do the Dixie cup process and toggle the fuel selector valve back and forth while running the fuel pump into Dixie cups.  Debris gets in that valve...   I have made this an annual process   ...  Cost is nothing and easy to do   
Same thing happened to me when I bought mine.. Except at 200agl on takeoff.   I did the above, then decided to send the spider, throttle body, and electric pump for overhaul, sense they were about 18years old .. 

Good advice. I just changed the fuel pump then had this problem. I'll drain and clean the gascolator as well.


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Thinking what would happen with a speck of dirt in an injector...

1) less fuel would be delivered to that cylinder compared to the others...

2) The amount of energy released would be less.

3) that cylinder would be first to peak, go lean, and stop operating (when leaned to the max)

4) the EGT would be kind of funky. As it is peaking first, it is not releasing as much energy as the others, so it's peak won't be as high.  Since the EGTs are relative, it could be hard to see.

5) The CHTs would also be helpful.  Less fuel burning in the affected cylinder would have a corresponding lower CHT than the others.  It may be enough when compared to previous flights to show a difference.

6) the Dixie cup test is a great way to test for blocked injectors.

 

other things that can cause a rise in EGT for a cylinder...

7)  a spark plug dying. As it dies, a few percent raw fuel goes out the exhaust still burning... causing a high EGT. Check if you have Champion plugs, if yes, check their resistance, scrap if resistance is high...

8) a not seating or sticking, burning fuel escapes the open-ish valve... causing a high EGT.  A camera sent down the spark plug hole is a good way to put an eyeball on the valve surface looking for the 'pizza' image...

 

9) now would be a good time to have that engine monitor upgrade....

 

PP ideas only.  Not a mechanic. My iPad battery died before I launched this post...

Best regards,

-a-

 

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2 minutes ago, Bayern Speed said:


Good advice. I just changed the fuel pump then had this problem. I'll drain and clean the gascolator as well.


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6 minutes ago, Bayern Speed said:


EGT was about 110 hotter than the rest. I was able to lean a bit before it started to vibrate getting progressively worse the more I leaned. I see the EGT as abnormal as my experience thus far has been no more than 30 degrees between all four until the vib started.


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You continue to focus on EGT temperature spreads which really don't mean anything.   I don't know if you have an engine monitor but I can't glean much from the information you've provided.   Everyone who's commented so far seems sure it's a fuel system issue. You seem inclined to tear into it. I hope that solves your problem.  If you had an engine monitor and a brief window of data (even if recorded with a pencil) any number of folks on this board could steer you in the right direction.  As a data point, I have been operating a 67F for 14 years. We've rebuilt the fuel servo, replaced all hoses, patched the tanks, and replaced two fuel pumps...in all of that, we've never had debris in the fuel system.  You know what we have had? Failed spark plug leads, failed mag coils and failed plugs. 

Why not rotate your plugs before you have someone tear into the fuel system?

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You continue to focus on EGT temperature spreads which really don't mean anything.   I don't know if you have an engine monitor but I can't glean much from the information you've provided.   Everyone who's commented so far seems sure it's a fuel system issue. You seem inclined to tear into it. I hope that solves your problem.  If you had an engine monitor and a brief window of data (even if recorded with a pencil) any number of folks on this board could steer you in the right direction.  As a data point, I have been operating a 67F for 14 years. We've rebuilt the fuel servo, replaced all hoses, patched the tanks, and replaced two fuel pumps...in all of that, we've never had debris in the fuel system.  You know what we have had? Failed spark plug leads, failed mag coils and failed plugs. 
Why not rotate your plugs before you have someone tear into the fuel system?

I will give it a shot. You think I could take plugs from a different cylinder and just swap them out? I do not have any data except what I originally posted. High EGT on number 1 that did not previously exist until this event. When leaning at cruise he vib starts after only a little bit of movement and gets progressively worse.


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Do you need to leave the ground to test your theory?

If it is a bad plug. You can probably find the name Champion on it.  Then you can measure the resistance of it.  If it is high, toss it out and get a new one...

To define high resistance, I would have to search for that...  it shouldn't be very hard.  Compare to new or the next one...

To see how common the plug resistance challenge is.  Search for Champion plugs...

https://mooneyspace.com/search/

Best regards,

-a-

Edited by carusoam
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I will try it on the ground at power and see if I get the same results. I don't want to fly her until I get this solved. Definitely will look at spark plug resistance and test that.


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12 minutes ago, Bayern Speed said:


I will give it a shot. You think I could take plugs from a different cylinder and just swap them out? I do not have any data except what I originally posted. High EGT on number 1 that did not previously exist until this event. When leaning at cruise he vib starts after only a little bit of movement and gets progressively worse.


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What is the actual EGT number? Was it in the 1400s, 1500s, 1600s? Normally a clogged injector peaks early and then goes lean of peak, by the time it starts causing a serious vibration the EGT would not likely be higher than the rest, it would be lower. Contrast that with an ignition issue where a dual ignition becomes a single ignition, flame front propagates slower, EGT rises because combustion event is still occurring during exhaust stroke and into the exhaust. 

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I had the same issue last year.  I had to run about 2 gal/hr higher than normal to stop the vibration on a flight home.  I went back out later to test it.  Ran up on the ground just fine.  Mags checked good.  I tried running to full power a lean on the ground, but i couldn't hold the brakes to get to full throttle.  So i tried a test flight. I noticed the #2 cylinder was at peak EGT during takeoff.  Got up to altitude and leaned.  Sure enough that cylinder went cold when the vibration started.  Next we did a flow test by pulling the injector, lifting the lines up, reconnecting the injectors to the lines, puting cups under each injector, and cycling the boost pump.  I noticed low flow in #1 and #2.  Next we pulled the injectors and cleaned by soking in Carb cleaner for a week.  Retested with no improvement.  So, i bought a set of Gami's and we installed them.  It's run great ever since.

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14 minutes ago, Bayern Speed said:

Ok, I. Did leave out some info. Number one was around 1460, the rest were around 1350. Thanks for helping me out!


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1460 is within the normal range, so indeed this could be a fuel issue. An ignition issue will often send EGTs into the mid to high 1500s or even 1600.

I fly a 67F and my EGTs peak anywhere from 1300s to 1400s depending on cylinder.

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13 hours ago, Shadrach said:

 

You continue to focus on EGT temperature spreads which really don't mean anything.   I don't know if you have an engine monitor but I can't glean much from the information you've provided.   Everyone who's commented so far seems sure it's a fuel system issue. You seem inclined to tear into it. I hope that solves your problem.  If you had an engine monitor and a brief window of data (even if recorded with a pencil) any number of folks on this board could steer you in the right direction.  As a data point, I have been operating a 67F for 14 years. We've rebuilt the fuel servo, replaced all hoses, patched the tanks, and replaced two fuel pumps...in all of that, we've never had debris in the fuel system.  You know what we have had? Failed spark plug leads, failed mag coils and failed plugs. 

Why not rotate your plugs before you have someone tear into the fuel system?

He just bought the plane though... it may very well have been sitting for periods of time that is not typical for the flying habits of most of us...   A plane that sits may develop some debris in the tanks from pieces of dye from evaporated fuel or dried out sealant...   this is exactly what I experienced... once I got all of it gone, it has not come back since...  I fly every week and usually keep the tanks near full..     That is not to say check plugs with bomb tester if available, or at least check resistance..     clogged injector on take off is not fun and it's too easy to try and flush the fuel system just to be sure, especially since the fuel pump was just overhauled.. .. I speculate some debris may have been dislodged from the selector valve when it was turned off, then back on during pump removal and install..  .. when I did the dixie cups while toggle the valve back and forth TONS of crap came out... 

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26 minutes ago, highlowfastslow said:

Could an induction leak be a possible culprit? My #2 would peak much earlier than the rest of my cylinders leading to vibration. Changing out some gaskets fixed the issue.


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Indeed it could, but induction leaks tend to be more obvious with the engine throttled back (more vacuum).

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Thanks for all the suggestions. I am headed to the airport. Going to check induction security, pull spark plugs first and check resistance/wear. If no finding there, I will pull the #1 injector. I'll let you know what I find. Will take it all one step at a time until I find a fault.

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Induction looked good, plugs ohmed out to 884 and 992, i think that is good, I'll check the board as I know I saw the resistance somewhere as 800-1200, injector was dirty and the hole was about half sized. Ultrasonic cleaned injector, looks great. Did not put it back together as I need some fuel lube for the injector and spark plug thread lube. Back to work tomorrow night so I might not get to fly till next Sunday or Monday.


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Cleaning all the injectors produced a good ground run and more even EGT, no more than 50 degree spread at full power. No flight today in Memphis with the bad weather and hail! Maybe tomorrow.


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