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Curtis B.
Curtis B., Technician
Category: Agriculture and Farm Equipment
Satisfied Customers: 28383
Experience:  Technican turned service manager on multiple lines of equipment and rental equipment.
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I have a Satoh Mitsubishi 30 HP diesel tractor, made in the

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I have a Satoh Mitsubishi 30 HP diesel tractor, made in the early or mid 1980's. It runs good almost all the time but occasionally if I rev it a little more than half and go downhill or perhaps disengage the PTO it starts to rev higher and higher on it's own. I immediately shut off the fuel and it will slowly go back to running normally. Also, when this sort of out of control running is going on there is a significant increase in black smoke from the exhaust and it runs very choppy. I have a good feeling if I was not able to catch this happening the engine will blow. I had a theory that perhaps there was water in the fuel or something so I topped of the tank with diesel. This may have helped a bit but the problem is still there.
Thanks, Tom

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Customer: replied 5 years ago.
The only reply so far is yours.
Thanks for your assistance, Tom

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This is a governor problem or the injection pump sticking. Have you checked the governor linkage, to see if there is any binding? Can you attach a picture using the paperclip Icon above the typing bar. I would like to see what the injection pump looks like. A gear driven pump or a pump that drops into a hole in the block.
Customer: replied 5 years ago.
I'd be happy to send a picture but unfortunately my wife has the camera, she'll be back next Wed. I can probably borrow a friends camera this weekend.
As far as linkage I can clearly see where it comes down and attaches to triangular shaped thing that's about 6" tall, 4" at the bottom and about 1" on the top. This is screwed on to the engine block near the front (meaning the screws that attach it are parallel to the ground, sort of like how you'd attach a water pump), just behind the radiator and very close to where the 4 diesel lines come in, so I'm gussing that's the governor and/or the injection pump (though I don't know). I don't see anything that looks like its dropping into a hole but I could be wrong. The linkage looks fine and seems to operate OK.
I'll do my best to find a camera today or tomorrow.
The governor weights and internal linkage would be inside the engine. There should be a cover, that allows access to the parts.
Customer: replied 5 years ago.
The only thing I see that looks like a plate is pretty close to directly under where the four diesel fuel lines go in. The plat is about 2" square with four bolts and a knob like thing in the center. It's about 4" behind (closer to the rear of the tractor) than where the throttle linkeage goes in. Should I remove that plate? Looks easy to do.
Thanks, Tom
That could be it. I would see whats there.
Customer: replied 5 years ago.
OK, I took the plate off. It turns out that knob like thing screws in and out and attaches to a piece of spring metal that in turn touches what looks like another spring metal contraption inside the compartment. So the knob is really some sort of fine tuning adjustment. It's all very clean. It sort of reminds of what a carburator on a weedeater looks like but bigger and with more complexity. There's some spring metal like connections and even a wire with yellow and black insulation attached to something. I moved the throttle to see if the metal things moved and it looked like one did but very slightly.
That is the governor linkage. I wonder what the wires are for? Never seen any wires inside any ones injection pump or governor housing.??
Customer: replied 5 years ago.
You know I just went and looked extra hard, it wasn't a wire with insulation but rather the end of a spring and in the light it looked like yellow and black insulation. Is there something I should be looking for that might be wrong? Or some adjustment?
Thanks, Tom
No, what you will have is something binding in the governor section. All I can tell you is that it has to be smooth and not bind, or it will do the race engine thing. That is because the governor is not cutting the rpm back like it should.
Customer: replied 5 years ago.
OK, I think I know what you're saying. What I am not clear about is what entails the "governer section". Is it what I can see or is there far more to it. Would it be OK to jiggle stuff around, maybe squirt some WD40 or something or do I need to take the whole deal apart.
Also, if it wouldhelp, I have a friend bringing a camera by in a couple of hours.
Thanks, Tom
There is a set of weights that turn to make the thing work. By the weights moving out as the rpm increases, it moves the governor lever to pull back on the fuel delivered. It runs in the housing, so it gets oil bath all the time. But that doesn't mean that it still can't bind up. Its one of those things that can be easy fix, or never fixed. Can you live with it like it is? Or is it time to start removing parts to check? You know that parts and information on this tractor is hard to come by!
Customer: replied 5 years ago.
It sounds like something I'll need to live with as what you're talking about is, I believe, beyond my capability (or patience). One thing that I do wonder about is this potentially dangerous. When it happens I slam the fuel to off and so far that has always worked but if I was too slow or something would I potentially kill the tractor (or myself)? Or maybe (I am hoping) there is some sort of max revving or auto shut off or something.
Thanks, Tom
No. That is what the governor is supposed to keep from happening. No auto shutoff. If in bind, just push in clutch so, tractor stops, and engine rpm only rises.
Customer: replied 5 years ago.
Just one last thing because of what you just said "just push in clutch so tractor stops and engine rpm only rises".
What I have been doing is when it starts to go high rpm is release the clutch (if it was in) and or re-engage the PTO really fast which puts some stress on the tractor and helps to decrease the runaway revving. Otherwise it seems like it might just go out of control.
So I'm curious if I should do it as you say and just wait out the high revving or if what I am doing is OK - or perhaps points to something else that is wrong.
Thans, Tom
Only thing that will cause the high revving in the governor or injection pump. Loading engine with pto is ok.
Curtis B., Technician
Satisfied Customers: 28383
Experience: Technican turned service manager on multiple lines of equipment and rental equipment.
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