Stumble in # 1

[MARZ]

Up in the pattern coming in for landing. Reduced to idle egt on number 1 dropped to almost nothing  noticeable Roughness.   Pulled to the hangar and ran it up to 1500  everything evened out. Back to idle same thing egt dropped and rough run

pulled and checked plugs - swapped number and number three plugs to see if the issue followed - no change

checked injectors - completely clean

flow tested the fuel divider. All even levels

checked intake tube on number one. Looks good - 

fuel pressure - 30 psi 

fuel flow about 1 gph at 700 

3.5 at 1500

Just had my annual, compressions were 79 across the board

@600 hours on the engine, 40 since top end

fuel pump?

[Andy95W]

Nice write up and initial troubleshooting.

You said that you checked the fuel injectors.  My suggestion is to just go ahead and clean #1 well and test run it again.  I've seen fuel injectors that looked perfect but weren't, a problem that would be amplified at very low fuel flows, i.e., idle.

Please keep us posted.

[MB65E]

Check compression, Swap plugs, probes, and injectors to known places and see what shakes out. Check the timing. Could have a lifter loosing oil pressure or becoming blocked when the oil P drops off.

What's the oil pressure doing?

Could pull the rocker box covers and measure travels of valves. Could have a valve sticking. What does it do on start up? 

-Matt

[neilpilot]

I fought a similar issue in my 64E for a couple of years, with the problem manifesting itself only once every 2-4 months. Turned out it was a torn fragment of a small o-ring floating about inside the fuel servo. When I finally suffered an off field landing that totaled the aircraft, I might have had the cleanest injectors possible, good spark, fuel pressure and compression but no fuel flow past the servo.

[MARZ]

57 minutes ago, neilpilot said:

I fought a similar issue in my 64E for a couple of years, with the problem manifesting itself only once every 2-4 months. Turned out it was a torn fragment of a small o-ring floating about inside the fuel servo. When I finally suffered an off field landing that totaled the aircraft, I might have had the cleanest injectors possible, good spark, fuel pressure and compression but no fuel flow past the servo.

Hmmm. Just out of annual - the screen on the electric fuel pump is upstream.   Maybe a piece of something got introduced there.  

[MARZ]

12 hours ago, Andy95W said:

Nice write up and initial troubleshooting.

You said that you checked the fuel injectors.  My suggestion is to just go ahead and clean #1 well and test run it again.  I've seen fuel injectors that looked perfect but weren't, a problem that would be amplified at very low fuel flows, i.e., idle.

Please keep us posted.

Actually I did soak number one in mek  

[neilpilot]

6 hours ago, Mike Ropers said:

Hmmm. Just out of annual - the screen on the electric fuel pump is upstream.   Maybe a piece of something got introduced there.  

 

5 hours ago, Mike Ropers said:

Actually I did soak number one in mek  

If your fuel pressure was steady and in the green, I think it's unlikely that the problem was due to a faulty fuel pump or fouled screen upstream of the pressure indication takeoff.

[Guitarmaster]

Sounds familiar.  Did it also have a hard time shutting down when you pulled the mixture to idle?  Kind of like dieseling?

Mine stopped doing it when I poked a piece of .032 safety wire in the vent hole on the fuel divider.  Problem solved.

Not saying that IS the problem, but it's worth a try the next time it happens.

[carusoam]

Summary...?

1) base problem:  #1cylinder loses its EGT...

2) suspects: fuel, spark, air, compression...

3) If The injector was causing the challenge, the engine monitor would be helpful showing the effects over a wider range...

4) If the spark was causing the challenge, the label on the spark plug says Champion right on it...

5) if air is causing the challenge, expect a loose intake tube, or worn seal between the tube and cylinder, or the other seal on the other end...?

6) compressions were measured and are in the proper range.

 

7) can you post a JPI graph?

8) can you check the resistance of your spark plugs?

9) is there no issue at higher power? Intake air leaks are more sensitive to low power/high restriction...

10) The fuel flow of 1gph seems kind of low compared to My 2.2gph for an IO550, leaned.... If you increase the mixture does the EGT improve?  

PP thoughts only, not a mechanic...

Best regards,

-a-

[MARZ]

FOUND IT!!!!!

nothing to do with the annual

everything to do with the reman heads @ 30 hours since top end.  

1 I did have a “diesel” effect when shutting down

2 my manifold pressure was High at idle

3 the old plugs were burning leaner than the rest

= intake leak

but you won’t believe the cause (found it whilst replacing plugs while troubleshooting )

it must have been loose for a while and finally fell out.  

[carusoam]

Great photo and follow-up, Mike!

Best regards,

-a-