Super M

[Big Boar]

I have a Super M that has trouble shutting off. I put it in road gear and let out on the clutch to kill it. What can I do?

 

[the tractior vet]

I have a Super M that has trouble shutting off. I put it in road gear and let out on the clutch to kill it. What can I do?

Well ing timing set to high, spark plugs wrong heat range, ideal RPM way to high , running to hot . cheap gas burning to hot . Carbon build up . And maybe it just wants to keep on working .

 

[used red MN]

Well ing timing set to high, spark plugs wrong heat range, ideal RPM way to high , running to hot .

How can the ignition timing have anything to do with this? All spark ignition engines I’ve ever worked on shut off the spark to stop the engine.
Big Boar
Of the other items mentioned, engine idle speed to fast is the main cause of this. Make sure the throttle is forward as far as it goes when shutting it off. Carbon build up probably second in line.

 

[Jim Becker]

How can the ignition timing have anything to do with this? All spark ignition engines I’ve ever worked on shut off the spark to stop the engine.

I think excess timing advance or overly high heat range spark plugs can cause excessive heat, making the spark plugs act a lot like glow plugs.

 

[used red MN]

I think excess timing advance

If he just got done pulling the arse off of it for 15 minutes straight at normal operating temperature and went to shut it off almost immediately with no cool down period this might be a legitimate answer.

 

[wh]

Has it been converted to alternator? Possible backfeed to ignition. Ignition Switch possibly not completely opening when shut off?

 

[DanielW]

Has it been converted to alternator? Possible backfeed to ignition. Ignition Switch possibly not completely opening when shut off?

That was my first thought. Somehow back-feeding to the coil (or faulty switch). But I think we'd need a bit more info on what's meant by, 'trouble shutting off'. Does the kill switch seemingly do nothing? In which case I'd suspect a wiring/back-feeding issue. Or does it kind of try to die and sputter but still keep in firing away for a bit? In which case I'd suspect dieseling out - must be running pretty hot in the chamber/plugs somehow.

If a 12V conversion, did you happen to use one of the pre-made spade connectors for Delco alternators that come with a diode built in (something like picture below)? Half the ones you buy these days have the diode in the wrong way around, so you'll go to kill the engine and it'll just keep running. No big deal to cut the diode out and solder it in the proper way around - just a little irksome. But you'd want to check the direction to confirm that's the problem first.

 

[used red MN]

Has it been converted to alternator? Possible backfeed to ignition. Ignition Switch possibly not completely opening when shut off?

Good point!

 

[Jim.ME]

Giving a good history can often help find the causes.

Is this a tractor you have owned for a while? If so, has it always had this issue, or did it just develop?

If you recently purchased it was it this way when you purchased it?

Have you ever completely tuned it up?

 

[the tractior vet]

How can the ignition timing have anything to do with this? All spark ignition engines I’ve ever worked on shut off the spark to stop the engine.
Big Boar
Of the other items mentioned, engine idle speed to fast is the main cause of this. Make sure the throttle is forward as far as it goes when shutting it off. Carbon build up probably second in line.

to far advanced or to far retard can cause this . . You just have not worked on enough stuff yet . Back in the late 60's and early seventy's we fought this on FO MO CO cars and trucks with the dual vac dist. Seen it on tractors . wrong plugs like the D 21 can cause this . ideal to high . The I H tractors with the fuel shut off on the carbs that is what that was for as the gassers of the time ran hotter and any carbon build up would glow and evern with no spark they would not shut down So plug the main fuel jet . When ya turned the key on the pintel came full off the main jet and tractor ran . Cars and trucks from back in my day were also fussy about a high ideal and would suffer run on , sometimes coughing back thru the carb and cause a carb fire . Mo Pars were great about this on start up when ing timing was set a T D C that ya found on the big blocks as factory set . And made for vary hard starting since ya had to crank them like starting a turbin . Bump the ing timing up to 10 degrees BTDC and the lite off better then a Ford. Just don't let the AIR NANNY'S see ya do it His S/M also may have big pistons and higher compression ratios along with the OLD ing timing as who knows if some one stuffed and old M dist on it with the 40 degree advance . SO with out putting a light to it we don't know the WHOLE STORY .

 

[MeanGene1]

In '78 I took my Galaxie over to Sears Point for the Wednesday Night Drags. It's a '62, and an original 406 engine car, but I had a 14:1 427 in it at the time, cross-ram intake, .660 cam, 40 degrees timing, 12 in slicks and 5.14 gears and loud like only a 427 Ford can be. Made one easy pass to make sure it was going to go straight, then came back and let it eat. 6000 off the line, almost... went up about 6 inches and the driveshaft went out the bottom. Hit the kill switch, but the hot 14:1 engine just kept running on, driveshaft going around clunk clunk. The starter is waving at me with the kill it signal, I'm trying, man, it won't quit running on. I finally pumped the gas a couple times and it quit. Yeah, lots of things will make a gas engine run-on with the ignition off lol

 

[used red MN]

Yeah, lots of things will make a gas engine run-on with the ignition off lol

Yep, I agree.. once the ignition is off the timing CANNOT be the source of the “run on”- “dieseling” whatever you want to call it. That dude telling me “I haven’t worked on enough stuff yet” doesn’t mean he’s the smartest. I don’t know in what condition an engine is “ideal”..strange that “idle” seems to interchange well with it.

 

[MeanGene1]

Yep, I agree.. once the ignition is off the timing CANNOT be the source of the “run on”- “dieseling” whatever you want to call it. That dude telling me “I haven’t worked on enough stuff yet” doesn’t mean he’s the smartest. I don’t know in what condition an engine is “ideal”..strange that “idle” seems to interchange well with it.

Well, he is pretty smart, and he has worlds of experience- and he's right. He's trying to help by sharing his knowledge and experience- maybe you should listen a little more

 

[used red MN]

Oops

 

[used red MN]

Yeah, lots of things will make a gas engine run-on with the ignition off lol

Well, he is pretty smart, and he has worlds of experience- and he's right. He's trying to help by sharing his knowledge and experience- maybe you should listen a little more

Seems odd to me that you agree with the item I say is not the cause of run on, yet you say he is right. I know this is an argument I can’t win in this ring, so I’ll drop it. Don’t want to knock his wobbly leg out from under him.

 

[Mark EC.IN]

Seems odd to me that you agree with the item I say is not the cause of run on, yet you say he is right. I know this is an argument I can’t win in this ring, so I’ll drop it. Don’t want to knock his wobbly leg out from under him

Having the timing too far advanced is probably the number one reason for "dieseling" in these old tractors. It makes the engine run hotter and creates hot spots in the cylinders. It's why they call it dieseling, it's firing without any spark.