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Old June 15th 21, 04:45 AM posted to rec.aviation.soaring
Kenn Sebesta
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Posts: 48
Default 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

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.

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.

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?


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.