ROUGH IDLE AFTER HOT START

[CDF219]

YES -- I searched this before posting and didnt find any threads on it so here goes.   Sunday I took a stroll up to Knoxville downtown Island, I have to tell ya if you have not flown into there its worth the trip. So a quick turn and upon restarting after fueling the engine was missing sounded like it was backfiring maybe on one cylinder a little. I did a run up and mag check and all was ok no missing and built manifold pressure just fine. While I was waiting to depart it was still missing a little so I took the runway with an abort plan in mind if it did not build power of if it were to start busting up, nothing I built power and full manifold pressure and max rpms climbed out no problems and kept an eye on things staying within glide to the airport for a few mins.

 

My flight back to Kennesaw Ga (KRYY) was uneventful and I made a quick drop in Jasper Ga to drop a passenger but never shut down, even there while at idle (1000 rpms) it was just as smooth as it always is.

 

Im hoping it was just because I started it while the engine was laready hot. I have the 1966 M20E IO-360-A1A

 

I used the Dave Magee hot start he showed me when I bought the plane

 

Dont touch anything start with Idle all the way out then add mixture when it fires.

 

Thoughts?

[Bob_Belville]

I am not an expert but I do have a '66 M20E and 2500 hours in Es. I would not be very concerned about initial roughness after a hot start. With hot fuel lines, potential vapor lock ISTM it takes a few minutes for the fuel feed to smooth out. I suppose you lean on the ground and that your plugs are good? 

[rbridges]

I was thinking some type of vapor lock, too.  

[CDF219]

Yes I lean while on ground and only 10 hours out of annual where plugs were good. It was a little concerning being the first time it has happened. I appreciate the info. Is this something that is just going to happen from time to time during hot starts? Is there any better way to avoid this happening?

[mike_elliott]

Most likely it is perc'd fuel from the lines causing this vapor lock like condition. If it persists on your next cold start, check your EGT's, Are they normal or high? If high, suspect  a stuck needle valve in your fuel servo.

[Marauder]

Yes I lean while on ground and only 10 hours out of annual where plugs were good. It was a little concerning being the first time it has happened. I appreciate the info. Is this something that is just going to happen from time to time during hot starts? Is there any better way to avoid this happening?

It happens almost all the time for me during the summer. Winter not as much. I have the A1A as well.

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[Bob_Belville]

It happens almost all the time for me during the summer. Winter not as much. I have the A1A as well.

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I was going to add the hot weather comment. In June 2012 I had the plane at the prop shop in Burlington NC for dynamic balancing. It was mid day, over 90 and we had to start and stop the engine several time to do the balancing. When time to go I could not get it to start and wound up flooding the engine. We had to pull the plane into the hanger shade, remove lower cowls and put a fan on the engine for an hour.

 

FWIW, the IO720 used in the Comanche 400 were almost impossible to hot start. The fuel lines running on top of that 8 cyl engine were notorious to vapor lock. As I understand it, that engine is essentially 2 of our IO360s.    

[DaV8or]

I have an F with the A1A and this is standard, normal ops for me as well. After a hot start it sounds and feels like a bad mag or something. Apply power and all clears up. I have been told this is pretty normal and that it has to do with fuel vaporizing in the injector lines. I'm not sure if Cardinal owners have this same issue, or if it's just a Mooney thing and due to the cowling.

[John Pleisse]

Lean for smoothness..

[N601RX]

Another thing that will cause a rough idle or loping is the check valve in the bottom of the intake.  It's just a small an fitting that has been modified into a check-valve by machining out the ID and adding a small plastic ball.  Dried up fuel will cause the ball to stick open and allow air into the intake while bypassing the fuel servo assembly.

[garytex]

Common for my A1A in an F in the summer on hot starts.  Scared e at first.  I think it is fuel vaporizing, clears up at richer mixture or sometimes you can stay lean and run the boost pump.

[Alan Fox]

Its the fuel boiling in the lines between the spider and the injectors , perfectly normal...

[CDF219]

As always I knew who to ask. Thank You all.

[tomn]

Chris, glad you enjoyed your visit to DKX - that's my home base.  I was out there Sunday but missed seeing your plane.  I have Bob's 66E that he owned years ago. Same issue as others have mentioned.  Hot starts are always difficult with this model.  I have found the best method for me to be the one described on an earlier thread where you open the mixture and throttle full for about 10 seconds prior to starting - set the throttle to produce 1000 RPM when running, and then start with mixture off then add fuel once she fires.  This has been working well usually taking about 20 blades or so to fire.  Lean to highest rpm after starting - you'll still get some roughness etc. as everyone has mentioned.  

 

Tom

[tomn]

It happens almost all the time for me during the summer. Winter not as much. I have the A1A as well.

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 Beginning to wonder about these avatars Chris......

[Marauder]

No worries Tom, I'm just monkeying around. :-)

[Guest]

I was going to add the hot weather comment. In June 2012 I had the plane at the prop shop in Burlington NC for dynamic balancing. It was mid day, over 90 and we had to start and stop the engine several time to do the balancing. When time to go I could not get it to start and wound up flooding the engine. We had to pull the plane into the hanger shade, remove lower cowls and put a fan on the engine for an hour.

 

FWIW, the IO720 used in the Comanche 400 were almost impossible to hot start. The fuel lines running on top of that 8 cyl engine were notorious to vapor lock. As I understand it, that engine is essentially 2 of our IO360s.

I own a Comanche 400, it is a bit harder to start while hot but not impossible. Once running it does idle a bit rough until enough fuel has flowed through the lines to cool it. It also has a cooling/purge system on the fuel servo which allows you to pump fuel through the servo and dump it on the ramp.

Most of the hard starting troubles were eliminated with better magnetos, in my case being able to fire all 16 spark plugs makes it very easy.

Clarence

[tomn]

No worries Tom, I'm just monkeying around. :-)

I enjoy waiting to see what we will see next! Keep em coming

[Marauder]

After a stressful week and after a couple of beers, I'm starting to feel like myself again