51 M runaway engine

[mailman1]

This PM I was out discing for sweet corn and it was running fine as far as fast or slow and then I noticed it start to increase in RPM and when I tried to slow down it just kept getting faster. I tried to shut off the ignition switch but to no avail. I was finally able to control the engine by using the choke to keep it from blowing. I had had trouble this winter with it not wanting to come down from a high idle but thought it might be ice or such in the carb or governor but the weather is fine now. Any thoughts?

 

[used red MN]

So you are saying that you shut off the ignition switch and the engine would not stop? Or do you mean the switch would cut out the engine but then return to high revs when you pulled it back out? If the engine didn’t stop when you shut off the ignition you have a miracle tractor!! My bet is you were nervous and confused about your tractor acting up in this manner and didn’t really shut off the ignition. Or there is something wrong with your switch or the ignition wiring circuit that doesn’t allow it to remove power from the coil. My guess is your throttle plate in the carb has come loose from its shaft. It may have already been loose this winter and normal “carb icing” allowed it to hang up on frost buildup on the inside of the carb throat. Pull the angled cover above the governor that has the vent tube on it.(#3 in the linked diagram) Have someone operate the throttle and see if the mechanisms in there move. The vertical rod coming up from the governor has to pull down to idle the engine. If that moves up and down it is very likely that the throttle plate came loose. Here is a link to what’s in there.
Messicks Farmall M governor linkage diagram

 

[mailman1]

No I wasn't nervous or confused I pushed the switch in and it would not short out, it did this before so I replaced the original switch as it was acting up then but still the same results. I checked the governor rod, spring, etc. and all are solid so next thing ZI will do is take the carb off and check the throttle plate. The only way I could kill the engine was to use the choke.

 

[caterpillar guy]

I have one question is this a mag or battery ignition? And if a mag are you sure you used the correct switch for a mag ? Just asking since they operate differently from each other Mag versus battery.

 

[Brownie450]

12 volt conversion?? Still 6 volts??
Jim

 

[Jim Becker]

Your old problem of the engine not shutting off was a preexisting problem that you didn't get fixed. From what you said, it sounds like your tractor was back-fitted with a magneto. If so, you either have a bad switch, a switch grounding problem or the wiring from the mag to the switch is only connecting part of the time.

Your new problem has nothing to do with the old problem. You just ran the tractor with one thing broken until something else broke. You address the new second problem as spelled out by used red MN.

 

[mailman1]

12 volt conversion maybe 20 years ago, battery ignition, and when it would not shut off when pushed in to off I assumed them switch was bad and replaced it. Now I went out and removed the carb. and all was tight but when I looked at the governor shaft that fits into the throttle shaft there was no tang as it had been completely worn off so I think that would explain the run away engine. Now this is a M&W G-11 governor shaft and housing and can you just buy that part or are they even in business anymore?

 

[Absent Minded Farmer]

12 volt conversion maybe 20 years ago, battery ignition, and when it would not shut off when pushed in to off I assumed them switch was bad and replaced it. Now I went out and removed the carb. and all was tight but when I looked at the governor shaft that fits into the throttle shaft there was no tang as it had been completely worn off so I think that would explain the run away engine. Now this is a M&W G-11 governor shaft and housing and can you just buy that part or are they even in business anymore?

Do you have the option of matching it up to a shaft from a standard IH governor? I want to say the tube & governor guts were different & the shaft is the same.

You can also change it out for an original setup if you're in a pinch. The Add Powr governor didn't add any horses, just made the throttle more responsive.

Mike

 

[used red MN]

I looked at the governor shaft that fits into the throttle shaft there was no tang as it had been completely worn off so I think that would explain the run away engine. Now this is a M&W G-11 governor

Must have been the over sensitive jerking response of the M&W governor that wore that tang off. Wonder if it was use on a square baler quite a bit? I don’t know if there is any derivative of M&W is still is operation. If it is I doubt you can get that part.
From a web search..
“Alamo Group bought M&W Gear Co. in April 1995 and shortened the name to M&W. The company was later merged into the Rhino AG brand, who further sold off the round baler line to Art's Way in 2010. Currently, Rhino is still using the M&W name.”..
There are probably some available on eBay etc. Likely going to have to prepare to fork over some dough since tractor pullers think those things are the real deal.
Prior to this even after you changed the switch would it still occasionally continue to run after you turned off the switch. Does your 12V conversion use a generator or alternator. If it an alternator is it a 3 wire like a Delco 10si? If so show us your wiring.

 

[mailman1]

I should mention that after I thought about it the time frame it was probably closer to 50 years ago. And after I looked for M&W I was wondering if I could maybe get a IHC tube and shaft from a salvage yard and use the M&W guts inside the governor housing?

 

[D Slater]

Depending on type alternator used and if exciter for alternator is tied into ignition wire to coil it could have a diode failing. Have used a IH shaft in M&W housing. Needed to modify but to long ago to remember for sure. Think shorten shaft a little and drill pin hole for lever that uses bolt to vertical shaft of governor. Most M&W didn't use the same vertical rod as M. M used pins in each end.

 

[m16ty]

First I’ve heard of a gas engine running away.

 

[flying belgian]

First I’ve heard of a gas engine running away.

Me too.

 

[Jim Becker]

I know of a guy with I believe, a BN. On the carburetor, the arm came loose on the throttle butterfly shaft and the throttle flipped open. Before he got it stopped, the governor exploded. Who would have thought the governor would be the part that blew up first?

 

[mailman1]

Does anyone know if the standard IHC M Governer throttle shaft part # 49788DXA for a M will interchange with a M&W G-11 throttle tube?

 

[BarnyardEngineering]

For future reference, if it ever won't shut off again, stop, get off, and pull the large wire off the coil. If it doesn't stop then, call a priest because you need an exorcism performed.

The odds of two ignition switches failing in closed is pretty slim. I suspect you have a wiring problem. If you are using power from the ignition switch to excite the alternator, and you don't have a diode installed, the alternator will backfeed power to the coil and keep the engine running.

 

[D Slater]

Does anyone know if the standard IHC M Governer throttle shaft part # 49788DXA for a M will interchange with a M&W G-11 throttle tube?

Not direct if you have throttle tube like most M&W. Picture of tubes from next size tractor down but about like you find differences on a M. Bottom tube is IH. Others are fore power governor. From memory think the shaft needs shortened a little and another hole for lever pin drilled in shaft. Have removed little off IH tube to use in some but can't remember if just H size when SH size carburetor used on a H. Can't remove much and keep bushing in throttle tube useable. May have something I changed laying around to refresh memory. Will post back if found.

 

[used red MN]

The odds of two ignition switches failing in closed is pretty slim. I suspect you have a wiring problem. If you are using power from the ignition switch to excite the alternator, and you don't have a diode installed, the alternator will backfeed power to the coil and keep the engine running.

You can also use a resistor in place of the diode, as well as an indicator light, essentially using the filament of the bulb as a resistor. I wonder if it has a resistor which is borderline to low to the required resistance. Then when it is shut off the alternator excite circuit feeds through the resistor providing a low voltage to the coil so it produces a weak spark but just enough to fire the plugs. If it has an indicator lamp the same could be true if the bulb was switched to one with lower resistance. I would need to do more research on the proper ohm value of a resistor for this application. One of the conversion diagrams I have calls out a rating of the indicator bulb as 200ma.

 

[mailman1]

For future reference, if it ever won't shut off again, stop, get off, and pull the large wire off the coil. If it doesn't stop then, call a priest because you need an exorcism performed.

The odds of two ignition switches failing in closed is pretty slim. I suspect you have a wiring problem. If you are using power from the ignition switch to excite the alternator, and you don't have a diode installed, the alternator will backfeed power to the coil and keep the engine running.

Is this what you are talking about?

 

[Absent Minded Farmer]

First I’ve heard of a gas engine running away.

Had it happen when the governor weights in my H let loose. Got a rebuild kit. Good to go!

Mike