Kubota Z482E overspeeds, I suspect governor problem

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srsm

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On starting my engine it races to full speed - only stopped by closing off air supply. Throttle and stop levers make no change. The engine has not been used for a few years except for occasional running at idle. The fuel is old as well which might have resulted in varnish or wax issues.
Governor is mechanical centrifugal type. My guess is that the governor is gummed up such that default full throttle stays stuck. Odd thing is that stop lever has no impact as I assumed this would be a fuel kill 'switch' and so bypass governor issues...

I've replaced fuel and no change (not a big surprise but a good start).

Any ideas (and is removal of governor for check an easy operation - I have no manual with that level of detail).

Cheers
 
A diesel will run on its lubricating oil when the piston rings are in bad condition and oil \ oil vapour gets into the combustion chamber. Always be prepared to put engine in forward so that the prop will prevent the motor to run to fast which could break a connecting rod.
If your engine has stood for a long time the problem may disappear when it has run for some hours and the piston rings loosen up again.
New engine oil\filter would also be a good idea.
Good luck,
Theo
 
The trouble with posting answers here is that I've never seen your engine, nor have I a clue what your installation is like.

There would appear to be no linkage between your throttle and your injector pumps. This may be a broken cable(s) or even a broken linkage or return spring on the engine itself.

It really depends upon the design of the engine, but often the throttle and stop mechanisms operate a rack, the position of which determines how long the injector pump stroke is, which determines how much fuel is injected into each cylinder.

If the pump is set to maximum stroke, and the rack is disengaged somehow, you'll get this efffect and closing off the air supply IS the only way to stop it.

The governor also operates this rack so even if the governor was working well, if it's disconnected from the rack, or the rack is damaged, again it'd have no effect.

A desiel WILL run on lub oil, but if this were the case with your engine, dipping the sump will tell you that. The oil level will be low and it will full of combustion products; you might even see smoke comiing from the crankcase breather.

You really need the manual for the engine to sort this out, or else turn the problem over to a professional marine engineer
 
Thanks Theo, Topcat

I'm getting a scan of a couple of pages of the manual on governors and fuel etc emailed so that will help.

I think the failure of the stop lever to do anything is the key. Don't think it is Lub oil as if the engine was getting diesel and lub oil as fuel it would be really lumpy (guess) and when the diesel is cut off via stop lever there would surely be a blip or uneven running after having had good fuel and then 'switching' to heavy oil leaking from somewhere. But nothing happens. That said not sure what combustion products would look like in the oil and I obviously stop the engine pdq.
I am ashore just now so cannot engage gear to slow the engine down.

Something has disengaged I reckon but odd thing is how it could have happened... fairly new engine and very light use.

I'll pass on any findings. Any more views?

Cheers
 
First of all check carefully for external springs on the throttle (or lack of) - see if a spring is dangling. Then, if you are certain that it is not burning on lube oil then try starting in gear; it all is safe, not over-revving and not causing problems, I would be inclined to let it run to operating temperature for a while like this and see if it frees up. If you get lots of smoke, vibration or it sounds bad, shut down but this might free up something that has got stuck from lack of use.
 
A friend had a car diesel run away, to destruction in his case.

The explanation he was given was of leakage past the rings pressurising the crankcase, then the crankcase breather blowing oily fumes or vapour into the air intake, which fuelled the engine. Lots of engines lead the breather to the air intake, if yours does then it might be worth disconnecting it and see if that makes a difference.
 
Forget the control levers and trace the bowden cables back to the engine. Operate the controls by the levers on the engine to see what is happening.

If it has been used for some years as you describe it could be stuck oil control rings or a blockage in the crank case breather that is allowing oil or vapour into the combustion space where it will burn without control.

You could try removing the injectors and pouring a slug of diesel into each cylinder to soak for a few days. Give it a good long churn with the decompressor lever to loosen things up a bit and then see how she starts and runs.
 
Chaps,

Consensus appears to be burning oil. If so, should there be clouds of blue smoke from the exhaust? I don't let the engine run for more than a few seconds (for obvious reasons) but the one time I caught a look at the back of the boat there was a reasonable puff of black smoke (not excessive). Not a hint of blue. Does this rule out lub oil burning?


A little more on my internal control lever problem theory. From the manual pages I was sent by Shanty (cheers Tim) the Stop Lever simply pushes the Fork Lever which moves the Control Rod on the Fuel Injector assembly to stop the fuel. If the Fork Lever connection to the Control Rod has failed then neither Governor nor Stop Lever operation will move the Control Rod which I reckon will slip to the full fuel default.

Another thought. The Stop Lever (when moved by hand instead of the stop solenoid) doesn't move much (perhaps 5mm - I will measure the travel later). What I can't recall is how far it used to move - perhaps this is normal. Tim might be able to help here (he has same engine).

So blue smoke or black smoke?

Regards
 
the majority of diesels start on full fuel position and the governor immediately controls the rack position to get it to idle speed, sounds as if the rack is stuck open or the governor mechanism is stuck, some of the marine engines have the governor in the timing chest, some in the fuel pump, your manual will give you an idea
stu
 
Checked another Z482 for Stop lever movement. My Stop Lever is definitely jammed it barely moves in comparison to proper operation.

Took the Control Plate off and the internal Fork lever that the external Stop lever moves does not budge. The Fork Lever connects directly to the fuel Control Rod on the Fuel Pump assembly and so stops the fuel (if only it moved). Given that the engine overspeeds the Fork Lever or Control Rod must be jammed in the full on fuel position.

So not a running on lub oil problem but no idea what can be causing the jam. At least I've isolated it to some extent.

Stuart
 
Problem solved!

Spoke to Kubota dealer and they confirmed that the Fuel Injector Pump would have seized up due to wax in old diesel. This required removal of said unit and then removal of cover plate and control rod slider. This exposed two little knobs which slide back and forth (actually rotate cylinders which obviously control the fuel). One of these rotated freely the other was jammed solid. Following instructions given by dealer I used a screwdriver to lever the knob which eventually started to move (amazingly tight given that cause was simply fuel that had become slightly waxy). It moved a bit and a gentle tap finally freed it.

Reassembly was a bit scary as the pump uses pistons controlled by the fuel camshaft and the pump pistons reset themselves when freed up so resetting down into the engine the pump wouldn't settle down and it appeared that something had foulled (until I figured out that the pistons simply needed compressed by screwing the device down).

Clue was that Stop Lever wasn't moving as far as it should and so something was jammed.
Job done.
 
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