(800) 853-2651
SHOP NOW

SM Dieseling

K

kopeck

Member
Last weekend I changed the oil on my '53 SM. When I got done with it I pulled it out into the drive and let it run for a few minutes at about half throttle. When I went to shut it down I cranked the throttle back to low idle, let it run for a few second and shut it off, which it did but then dieseled for a few more seconds (might have even been running backwards).

I've had this thing for a little over a year but have hardly run it, in fact it was the first time I had changed the oil on it. It does have fresh gas in it though with stabil added.

I know last year I was using it to move wood around on a pulp cart and it backfired once when shut it off.

What do you think? I'm going to check the timing and make sure that's right and I also have new set of Autolite 3116s for it (it has Champion UD16s in it right now). Maybe back the idle jet out a bit too?

The thing sounds very strong and runs very smooth, starts well and does not smoke. Somethings just bit off somewhere. I think I'm going to try plowing with it this fall, I would like to figure our what's going on before I really put a load on it.

K
 
A couple thoughts: first, make sure the idle speed is set low enough (around 400-450 rpm). Idle rpm set too high will encourage "dieseling".
Second, if the problem persists, put the transmission in 4th or 5th gear, apply the brakes, and let out the clutch as you turn off the ignition switch.
 
Could be the head is carboned up. Carbon gets hot and continues to ignite the gas. This could happen if you don't work it hard enough and/or the carburetor is too rich.
 
Comon' now, think about it,

When ya shut off the switch, there is no timing. So, yer sparkplug change and the timing check is a total waste of your time.

You've got a hot chunk of spinning iron being fed fuel.

Allan
 
Dieseling, a backfire or an occasional backward spin is not unusual for a Super M at shutdown .

Working the engine hard for a few minutes to burn out carbon deposits sometime helps. So also does switching to a higher octane fuel. And as others point out adjusting the low idle RPM down as slow as possible - 425 RPM or so - and letting the engine idle a minute before hitting the switch can help.

However DON'T mess with the ignition timing - it will accomplish nothing (there's no "spark timing" when the ignition is switch is off!)

Incidentally dieseling at shutdown hurts nothing. Our two SM's have done it for 55+ years with no ill effects whatsoever.
 

Dieseling on a gasoline motor is caused by a red hot carbon deposit in the cylinder wall igniting the fuel, with a car you can fix this by running it taking the air cleaner off and pouring a quart of water as fast as it will take it without dying, this cold water breaks the carbon apart harmlessly. With a tractor I dont know how you could get the water in there being that the carb is on the side of the engine.
 
Mine does the same thing -- I pull out the choke immediately after shutting it off. Works every time for me.
 
Dieseling with automatic transmission can be a problem but on manual just put it in top gear and let clutch out....it will stop.
 
Dieseling with automatic transmission can be a problem but on manual just put it in top gear and let clutch out....it will stop.
 
Thanks guys, I didn't know it was such a common problem.

The reason I mentioned the timing is I've seen a truck that ran hot once due to timing issues (pretty sure it was advanced). I know after the button is pushed timing is no longer an issue.

Sounds like it could be carbon. I doubt it's been worked hard for some time. I know in small single cylinder engines people like to use Marvel Mystery oil to help burn it off. Maybe it's just snake oil, I've used ATF in my diesels in the past with pretty good success.

K
 
If it is indeed carbon, plowing with it is a good way to cure the problem.

Get 'er good and hot and the carbon will burn off.

I've also had good luck with Seafoam sprayed into the intake as much as the engine would take without dying.
 

Definitely dont use the choke to shut it off like that, then you wash all of your cylinders down right before shutting it off. The top gear thing is a better idea.
 
You must log in or register to reply here.

Similar threads

M
1950 IHC M throttle response
Replies
8
Views
466
mailman1
M
RedMF40
Chainsaw is high-speed "dieseling"
Replies
5
Views
593
RedMF40
RedMF40
J
Metering shaft
Replies
4
Views
300
jhncp
J
Dillsburg 560D
  • Question
Farmall 656 shut down issues
Replies
2
Views
388
used red MN
U
M
Farmall 140 Cylinder gets tight after one minute of running.
Replies
17
Views
629
560Dennis
560Dennis
Tractor Parts Tractor Manuals

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Copyright © 1997-2024 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy

Back
Top