Russia AC-5M Engine Problem

Dieseling sounds bad. If there truly are deposits causing auto-ignition in your engine than that needs to be addressed ASAP, as that can lead to engine destruction within 60 seconds.

I wonder if you don't have the identical problem I had with my AC-5M, which is where the magneto ground wire failed leaving me unable to short the spark plug to ground. I was only able to stop the engine by pulling the fuel shutoff. That takes quite a while because of the amount of fuel line between the tank-mounted shutoff and the carburetor.

I would second the recommendation to set the throttle such that bringing it all the way back will completely shut-off the air intake, killing the engine.

P.S. The group has moved to https://groups.io/g/ac-4gliders.

On Monday, June 14, 2021 at 3:02:56 PM UTC-4, Dan Marotta wrote:
Increasing throttle after turning off the ignition might just make it
diesel longer. Perhaps reducing the idle RPM with the idle adjustment
screw would help but you may then need to apply a little throttle to
keep it running. I recall a 1973 Chevelle that I owned that had an
anti-dieseling solenoid which kept the throttle opened enough to idle
with the ignition on and, when the ignition was turned off, the solenoid
allowed the throttle to close completely choking off the air.

Dan
5J
On 6/13/21 5:38 PM, Branko Stojkovic wrote:
On Sunday, June 13, 2021 at 3:36:32 PM UTC-7, Dan Marotta wrote:
Do you have a fuel cut off valve? How about a choke lever, pulling the
choke on a hot engine might kill it.

Dan
5J
On 6/13/21 9:34 AM, Branko Stojkovic wrote:
I have been having a problem with shutting down the MZ35 engine in flight on my Russia AC-5M. The engine keeps running (dieseling) for a couple of minutes until it cools down enough and finally quits. I changed the spark plug, took off the cylinder head and cleaned the carbon deposits, but to no avail. Does anyone have any ideas on what I could try next? Thanks in advance!

BTW, there used to be good AC4 a Yahoo group before Yahoo shut all their groups down. Has anyone archived it?

Branko
XYU
Thanks for the suggestions Dan. The fuel cut-off valve is installed in the engine bay and there is no choke. I haven't tried giving it full throttle, do you think that might work.

Branko
XYU

On Monday, June 14, 2021 at 8:45:43 PM UTC-7, Kenn Sebesta wrote:
Dieseling sounds bad. If there truly are deposits causing auto-ignition in your engine than that needs to be addressed ASAP, as that can lead to engine destruction within 60 seconds.

I wonder if you don't have the identical problem I had with my AC-5M, which is where the magneto ground wire failed leaving me unable to short the spark plug to ground. I was only able to stop the engine by pulling the fuel shutoff. That takes quite a while because of the amount of fuel line between the tank-mounted shutoff and the carburetor.

I would second the recommendation to set the throttle such that bringing it all the way back will completely shut-off the air intake, killing the engine.

P.S. The group has moved to https://groups.io/g/ac-4gliders.
On Monday, June 14, 2021 at 3:02:56 PM UTC-4, Dan Marotta wrote:
Increasing throttle after turning off the ignition might just make it
diesel longer. Perhaps reducing the idle RPM with the idle adjustment
screw would help but you may then need to apply a little throttle to
keep it running. I recall a 1973 Chevelle that I owned that had an
anti-dieseling solenoid which kept the throttle opened enough to idle
with the ignition on and, when the ignition was turned off, the solenoid
allowed the throttle to close completely choking off the air.

Dan
5J
On 6/13/21 5:38 PM, Branko Stojkovic wrote:
On Sunday, June 13, 2021 at 3:36:32 PM UTC-7, Dan Marotta wrote:
Do you have a fuel cut off valve? How about a choke lever, pulling the
choke on a hot engine might kill it.

Dan
5J
On 6/13/21 9:34 AM, Branko Stojkovic wrote:
I have been having a problem with shutting down the MZ35 engine in flight on my Russia AC-5M. The engine keeps running (dieseling) for a couple of minutes until it cools down enough and finally quits. I changed the spark plug, took off the cylinder head and cleaned the carbon deposits, but to no avail. Does anyone have any ideas on what I could try next? Thanks in advance!

BTW, there used to be good AC4 a Yahoo group before Yahoo shut all their groups down. Has anyone archived it?

Branko
XYU
Thanks for the suggestions Dan. The fuel cut-off valve is installed in the engine bay and there is no choke. I haven't tried giving it full throttle, do you think that might work.

Branko
XYU

Thanks Dan and Kenn, good suggestions!
I'll definitely try adjusting the throttle as you both have suggested.
Also Kenn, thanks for the link to the new AC4 gliders user group. I signed up right away.
Cheers,
Branko
XYU

On Tuesday, June 15, 2021 at 10:30:26 AM UTC-4, Branko Stojkovic wrote:
On Monday, June 14, 2021 at 8:45:43 PM UTC-7, Kenn Sebesta wrote:
Dieseling sounds bad. If there truly are deposits causing auto-ignition in your engine than that needs to be addressed ASAP, as that can lead to engine destruction within 60 seconds.

I wonder if you don't have the identical problem I had with my AC-5M, which is where the magneto ground wire failed leaving me unable to short the spark plug to ground. I was only able to stop the engine by pulling the fuel shutoff. That takes quite a while because of the amount of fuel line between the tank-mounted shutoff and the carburetor.

I would second the recommendation to set the throttle such that bringing it all the way back will completely shut-off the air intake, killing the engine.

P.S. The group has moved to https://groups.io/g/ac-4gliders.
On Monday, June 14, 2021 at 3:02:56 PM UTC-4, Dan Marotta wrote:
Increasing throttle after turning off the ignition might just make it
diesel longer. Perhaps reducing the idle RPM with the idle adjustment
screw would help but you may then need to apply a little throttle to
keep it running. I recall a 1973 Chevelle that I owned that had an
anti-dieseling solenoid which kept the throttle opened enough to idle
with the ignition on and, when the ignition was turned off, the solenoid
allowed the throttle to close completely choking off the air.

Dan
5J
On 6/13/21 5:38 PM, Branko Stojkovic wrote:
On Sunday, June 13, 2021 at 3:36:32 PM UTC-7, Dan Marotta wrote:
Do you have a fuel cut off valve? How about a choke lever, pulling the
choke on a hot engine might kill it.

Dan
5J
On 6/13/21 9:34 AM, Branko Stojkovic wrote:
I have been having a problem with shutting down the MZ35 engine in flight on my Russia AC-5M. The engine keeps running (dieseling) for a couple of minutes until it cools down enough and finally quits. I changed the spark plug, took off the cylinder head and cleaned the carbon deposits, but to no avail. Does anyone have any ideas on what I could try next? Thanks in advance!

BTW, there used to be good AC4 a Yahoo group before Yahoo shut all their groups down. Has anyone archived it?

Branko
XYU
Thanks for the suggestions Dan. The fuel cut-off valve is installed in the engine bay and there is no choke. I haven't tried giving it full throttle, do you think that might work.

Branko
XYU
Thanks Dan and Kenn, good suggestions!
I'll definitely try adjusting the throttle as you both have suggested.
Also Kenn, thanks for the link to the new AC4 gliders user group. I signed up right away.
Cheers,
Branko
XYU
Does it have a mixture control? If so check function.
UH

Does it have a mixture control? If so check function.
UH

No mixture control. The Til;otson HR-194A carb is a automatic adjustment diaphragm type. There's a fuel shutoff valve but it's located on the fuel tank and there's probably 2m of fuel tubing between that valve and the carb.

I had a funny moment when I last used the shutoff. I had run the tank almost dry and replaced the 100LL with some ethanol-free gas I'd purchased. After closing the valve, and stopping the engine, I got out and manually reopened it from underneath the tank. The fuel in the clear fuel filter instantly snapped from blue to orange.

I'd never seen orange gas before and so I started furiously searching online to see what I had broken. Turns out it was just the color which arose from mixing the ethanol-free's dye and the 2-cycle oil. Because of the shear amount of suction-- which had effectively collapsed all the fuel tubing-- the orange gas mixture was pulled all the way from the tank to the carb in a heartbeat.

Derp.