dieseling????

V8S10

Member
hey guys! having a problem with my M dieseling when you shut it off and having to put it in 5th gear right away to kill it other wise it will diesel when it shuts off and keep running.. it will only do it when its warm, it never gets warmer then 190 degrees and ussually runs a little less then that.. i dont have a problem with it when its just sitting idling for a while or if i use it to move something in the yard with it.. im running straight 110 octane that i get from a local race shop, i put the tractor in 5th gear before i hit the kill switch and let the clutch out easy as i hit the kill switch and then it wont diesel. anything i can do?? run a different fuel? ive mixed in for every 5 gallons of 110 i use like 2 and 1/2 gallons of 93 to make the fuel last longer as the 110 isnt very cheap
 
If the engine has had time to build carbon deposits on the pistons or head, that carbon can glow and cause a "run on" situation. If not, then its obvious that you must have high compression or else you wouldn"t us the 110 fuel. Make sure the carb plate shuts down and then if it still diesels, use 110 straight
 
Ignition timming has nothing to do with dieseling. Ignition is turned off, so cant be timming. What compression ratio are you running? When shutting off engine you should be at a complete idel. Sounds like you need better fuel
 
yes im running an lp head and high dome 4 1/8 pistons in my farmall M it did the dieseling thing when i ran 110 straight also..
it runs very nice on the dyno around 65 horse so far .. hadnt had much time to monkey with the carb yet. i no the timing isnt off because ive timed it just right like the it manuel says and ive even checked the in the dristrubuter for the rotor to be on 1 on the dist. cap when the piston is at the top of the compresion stroke. ill maybe try the throttle plate in the carb as my m idles a little higher with the stiffer spring i use
 
garry is right ignition isnt problem but plugs heat range could be . try a plug two steps colder than what you run now
 
Remember those electric shutoffs on the load jet on IHC combines and 6 cyl gas tractors. you need one. or a electric solenoid for your idle screw to set against. Then when you shut off the ign it will snap in and the butterfly will be plum shutoff. It will not run on if it can not get any gas air or ign. Almost all cars and trucks had a solenoid on the carb in the 60's and 70's. Vic
 
I read the replies: it will need to idle slower or as suggested, you will need an idle speed solenoid to drop the throttle plate shut when you turn the ignition off. It would be interesting to know what difference it would make if you could work the engine hard for about an hour. (Maybe blow out some carbon deposits)
 
Just because you are buying 110 octane doesn"t mean thats what you are getting. Go to a local airport and buy some certified 100 octane gasoline and see what it does. An old buddy of mine used to bracket race and he would always run more consistantly with av gas because it was always guaranteed to be 100 octane, the stuff from the barrel who knows!
 
alright ill try the throttle plate thing works, and i have the silanoid fuel shut off deal because i have a bowl off of a 301 combine engine annd i just used the brass nut and screw like an M would have. im looking into maybe this winter stroking the tractor some .
 
hey guys thanks for all the help! i got the problem fixed by adding the fuel shut off siliniod! no problems what so ever! Thanks again guys!
 
just because you buying 110 fuel look at the label look at the true motor octane, not what pump octane is.....go higher octane may fix problem......like gary mention....
 
Gary is right plus timing have nothing to do with dieseling
When there is no spark . When you take 93 and mix with
110 you only have 95 stop be cheap and run all 110
And it will stop dieseling. If it less 12 to1 I have had this
before and was run 110 and had to go 118 to stop it
 
Gary is right plus timing have nothing to do with dieseling
When there is no spark . When you take 93 and mix with
110 you only have 95 stop be cheap and run all 110
And it will stop dieseling. If it less 12 to1 I have had this
before and was run 110 and had to go 118 to stop it
 

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