Deiseling in IO360A3B6D

[PTK]

I think I experienced some dieseling yesterday in my engine.

 

On shut down I normally cut the mixture, mags off and master off in that order.

 

Yesterday after I cut the mixture the engine didn't quite die like it normally does but kept going for several prop revolutions. 

 

I just had new spark plugs put in but I don't think it's related.

 

Has anyone else experienced this in the injected engine?

[wishboneash]

Carbon deposits on pistons? That's one of many possible reasons.

[jetdriven]

Did you do the mag grounding check before shutting it down? Was the engine very hot? We had a very warm engine and it ran for a few seconds after killing it with the mags.

[Bob_Belville]

I don't think what you are describing is dieseling. Dieseling occurs when an engine continues to run after the ignition is cut off which is done in our airplanes but turning off the mags.

 

If your engine doesn't want to stop with the mixture pulled full out it would be because the fuel is not completely cut off. You probably need to check the mixture cable to be sure it reaches stop. 

[testwest]

Dr. K, I had this problem as well. Unfortunately it required an overhaul of the fuel servo, we did check the valve in the fuel divider (and I would do that first, just like rogerl suggested above) and for us the divider was OK. The servo overhaul was pretty quick but pricey.

 

Aircraft Spruce has servos for exchange - cheapest is an RSA-5 type servo for $1383 (overhauled) check your dash number and shop around, after you confirm the flow divider (spider) is OK.

 

[PTK]

Thank you all for your input.

I cut the mags after the mixture but if made no difference. I'm hoping it was just temperature related as Byron suggests but I do 't feel the engine was much hotter than any other time.

Would vapor in fuel lines cause this?

Norman how is the flow divider checked if it's ok?

[mooniac15u]

 Just hope that the fuel shutoff isn't needed someday for shutdown if a p-lead falls off ...

 

There's always the fuel selector valve.

[marky_24]

I think I experienced some dieseling yesterday in my engine.

 

On shut down I normally cut the mixture, mags off and master off in that order.

 

Yesterday after I cut the mixture the engine didn't quite die like it normally does but kept going for several prop revolutions. 

 

I just had new spark plugs put in but I don't think it's related.

 

Has anyone else experienced this in the injected engine?

How many is several? 2-3 seconds? 10 seconds? if it just took a few seconds to die after the mixture was pulled i would think it could be vapor/heat related but if it was more like 10 seconds then you have to look at the injection system. 

[PTK]

Thank you Marky.

I'll pay more attention to time if it does it again.

It looked like it normally does at shutdown. The prop coming to a stop but not quite. It kept wanting to come alive. I cut the mags and it didn't seem to make a difference.

[Cody Stallings]

I had that problem when the RSA5 Fuel Servo decided it was time to go to the shop. It would not die with the mixture, had to cut the fuel off an wait............an wait......... An wait some more. Then finally it would shut down.

[jetdriven]

Check the mixture control actually makes the arm on the servo hit the ICO stop. The RSA injector doesn't cut fuel off completely. It simply brings it to such a low level the engine cannot run on it.

[MB65E]

Idle mixture might need adjusting. In PHX summer vs winter, I always needed to adjust it...

Just hot I bet!

-Matt

[jetdriven]

Matt, the idle mixture has no effect on ICO. iCO is a separate cam disc which rotates to cover a hole.

[Guest]

The most likely cause of poor shut down with run on is a sticking plunger in the fuel flow divider.

Remove the 4 screws on top, carefully pull the plunger and diaphram out, if its sticky polish the plunge with very fine scotch brute, reassemble and test.

Clarence

[MB65E]

Thanks Byron,

I'm just curious why the tempature has an effect on the ICO. Less air more fuel richer mixture?

[jetdriven]

No, you're right, temperature (air density, actually) can affect idle mixture. But ICO is a separate part of the fuel servo. I don't think adjusting the idle mixture won't have an effect on ICO unless it was super flood like rich, which might take it a few seconds to clear out and quit running when you pull the mixture.

Colder air is more dense at the same MSL altitude. Denser air requires a richer idle mixture than a hot day (higher density altitude). My idle mixture is set for almost zero rise but I still lean it to 3/4 on the ground. In the winter it's full rich for a couple minutes then lean less than I can in the summer.

[MB65E]

I see... I've always done the rise 75-100 rise thing at 900rpm. But having less rise might help it run cleaner on the gnd? I'd like to here some one give a refresher presentation on both TCM and Lyc fuel injection again! Lol.

I was taught what the items do, but the corlation between each component and the entire system is where it counts!

I still wonder what Pete's rise is...

-Matt

[fantom]

Ease the mixture out more slowly....

 

If that doesn't help, put some CamGuard in the engine. Works every time!

[PTK]

Thank you all for your input. This education is invaluable!

My plan is to start with the simple things first and work my way up to the servo if needed.

So I'll start with checking the mixture control making sure it makes the servo arm hit the ICO stop.

I'll also be sure to ease the mixture out slowly.

We'll see how these work. Then if needed I'll have the fuel divider checked making sure the plunger doesn't stick.

(For the record Clarence, thank you but I'm not removing any screws anywhere let alone sand anything with scotchbrite! that's when I recruit the professionals! I'll let Larry at Weber's handle that!)

Then as last resort the servo goes out if need be.

Is this a good plan?

[Guest]

Sounds like a good plan. I'm sure you'll get to the cause of your troubles with minimal effort.

Clarence

[PTK]

Have done a lot of flying since that last dieseling incident. Am happy to report that it has not recurred!

 

One change I did make is to dial the mixture to cutoff rather than pulling it. Not sure if this is related or not.

 

Which brings me to my question. What do you folks do?  pull the mixture or dial it out to cutoff? 

 

Also another question which may be related. The first item in my shutdown checklist in the POH says "Throttle--IDLE at 1000 to 1200 RPM until cylinder head temperature starts to drop."

 

I don't really wait for CHT's to drop anymore than they already have. They're already are in the low 300's or high 200's.

 

How long do you guys wait?