On Fri, 21 Mar 2008 07:51:59 -0400, "Roger Long"
wrote:

You say that mechanics have not been able to fix the problem. Are you sure
they did not try these adjustments?

I'm beginning to suspect that you have a problem inside the governor itself,
corrosion, debris, slight manufacturing defect or tolerance drift is making
it sluggish to react. The weights stick slightly and then let go.
Increasing the rate at which fuel flow can be increased during accelleration
might compensate but, if this is the case, could lead to further instability
because of "overshoot" when the governor weights unstick.

It also sounds like you might have too large an alternator. Prop demand
won't, or shouldn't, change suddenly but a sudden load like a large
alternator on a small engine like this may simply be outside the design
envelope of the fuel control system. Actually, it is probably right on the
edge so one engine is OK and the other has problems. This whole
installation was about 30 feet long so it was pretty impressive.

Here's my governor sea story:

I worked on the repowering of a large oceanographic vessel. We installed
two EMD engines (same as in railroad locomotives) that had been in a
government warehouse since about WWII. Each gearbox had a shaft running
back to DC drive motors taken out of an older diesel electric vessel and
converted into generators to run the ship's bow thruster. These motors were
about 5 feet in diameter and I put a big flexible coupling on the front of
the generators that was like half of a car tire bolted to a big metal disc.

When we first fired up the engines, one ran fine. The other began surging
and lunging back and forth as soon as the generator was clutched in with
such violence that we could see the generator beds and ship structure flex.
It was astounding and alarming during the second or two it took to grab the
PTO handle back into OFF. The whole installation was about 30 feet long so
it was pretty impressive. Both were identical so it was a real mystery.

They called in an EMD expert from Texas who flew up. We stated up the
engine, clutched it in, watched the lunging for 2 seconds and shut down.
The expert hopped up on the engine, took the cover off the governor and
said, "Get me a drill with a 3/16" bit." He drilled a hole in something,
fiddled around for about 10 seconds, put the top back on, and started to
leave. We asked if he wanted to see it run and he said, no, he knew it
would work. It did. He was on the ship for about 20 minutes.

It turned out that one engine had a marine governor and the other a railroad
locomotive governor. The railroad governor had a second set of weights
that, when sudden load was put on the engine, would rapidly increase the
fuel flow. This was so the engine wouldn't bog down when the slack came out
of the couplers of the railroad cars. When we clutched in the PTO, the
rubber tire flex coupling would wind up as. The load would cause the
governor to goose the engine and the timing was such that the unwinding of
the flex coupling would exactly match up with the time it took for the
governor to react. The impulse went back and forth magnifying each time
like a huge mechanical laser. All the fellow from Texas did was drill a
hole in the two discs that held the two sets of weights and insert a pin to
disable the goosing function.


You flew him in from Texas?

Good Lord I must be getting old. EMD guys used to be all over the
place. A very common engine at one time, We had a whole generator
house full of them at one time in Irian Jaya.

Then the company decided to modernize and sold all the old engines and
replaced them with turbines. do you have any idea how fast the shut
downs work on a turbine?

Once they got the new plant set up the entire site used to go down
several times a day. One turbine would hiccup and go off line. The
remaining units would sense an overload and Bam they would all shut
down.

That story makes me wonder, do any of the smaller commercial vessels
use turbines?




Bruce-in-Bangkok
(correct email address for reply)

On Mar 21, 1:51 am, "Roger Long" wrote:
You say that mechanics have not been able to fix the problem. Are you sure
they did not try these adjustments?

Well, the last folks had the engine for over a month and might have
fiddled with it, but I don' think they did. 100% or respondents say
"fuel restriction or air in fuel" when I describe the problem, but so
far the ones who've attempted to fix it have failed. All the obvious
things have been done multiple times.

I'm beginning to suspect that you have a problem inside the governor itself,
corrosion, debris, slight manufacturing defect or tolerance drift is making
it sluggish to react.

Yes, that could be the case. As Bruce has pointed out these are well
made engines and it would be a rare affliction, but basically all
that's left unchecked is the governor and its adjustments and the
injection pump. Also, the fact that there seems to be a change when
the engine warms up seems suggest to me that there might be a change
in tolerances w/in the gov mechanism itself... And, makes the
injection limiter a less likely culprit. The injection limiter is a
bit of a hail Mary, but seems easy...

It also sounds like you might have too large an alternator.

In practice there's no doubt that the alternator is too large for that
engine. But, the identical machine works on the left side...

-- Tom.

On Mar 21, 12:41 am, Bruce in Bangkok wrote:
The Manual quite emphatically states that the high speed adjustment
and the Fuel Injection Limiter should not be adjusted and will void
the guarantee if the seal is broken.

Oddly enough my manual doesn't say that for the injection limiter but
does for the no-load... But I'm sure you're right, why else would
they seal it?

I'm not sure whether the Fuel Injection Limiter has a spring loaded
plunger in it or not. Detroit Diesel engines had a similar device but
in their case it was to limit surge at idle.

Yes, the manual shows a spring in it (though the manual isn't always a
perfect indicator of what is actually installed).

.. The screw should have a
slot so it can be adjusted with a screw driver, if not scratch a line
on the screw so you can tell how far you have turned it.

Right, in practice the nuts and washers are all tight against each
other and no part of the shaft is showing. The adjuster is a hollow
threaded rod with a spring inside of it. The slot on the top of the
rod is the spring retention screw. Not sure if turning it ccw will
undo it or the control shaft. Assuming nothing moves when I take the
acorn I suppose I could make a mark on the shaft w/respect to the lock
nut.

Thanks!

-- Tom.

On Mar 21, 9:53 am, "Roger Long" wrote:
You might try swapping the alternators (and voltage regulators if separate)
from side to side. It could be that the governors are right on the edge of
not being able to cope with the electric loads and there is a difference in
how the alternators are functioning.

That's an interesting thought. Both are controlled by my Ample Power
controller and share the same loads (at least in theory). The port
engine seem quite cheerful with its load (good throttle response, no
smoke, smooth running). The starboard engine loses power but doesn't
smoke or run rough when asked to do the same task. I have had the stb
alternator rebuilt and that didn't change anything.

Just out of curiosity, how many hours on these engines?

1,338.5 port and 1,354.8 stb.

-- Tom.

http://www.alliedkenco.com/catalog/a...id= undefined

On Mar 21, 1:40 pm, "Roger Long" wrote:
... Everything in the QM, and I strongly suspect on your GM as well, depends on
balances of spring pressure and there are numerous points where a bit of
corrosion, burr left over from manufacturing, etc. could create exactly the
symptoms you describe.

Yes that sounds like the same beast. I've sent you a few scans. Hope
they aren't to horrible.

You probably need to have the back cover taken off this engine and
everything in the governor system checked out. It doesn't look like rocket
science.

Yes, but it is a PIA. Actually, I was just looking at the injector
pump and I think I can get it out of there (I'll have to rescue the
shims by feel, but... So, I might pull it and have it over to the
shop before I have the front of the engine off. Still, turning one
little screw sounds soooo much easier...

Cheers,

-- Tom.

On Fri, 21 Mar 2008 11:16:02 -0700 (PDT), "
wrote:

On Mar 21, 12:41 am, Bruce in Bangkok wrote:
The Manual quite emphatically states that the high speed adjustment
and the Fuel Injection Limiter should not be adjusted and will void
the guarantee if the seal is broken.

Oddly enough my manual doesn't say that for the injection limiter but
does for the no-load... But I'm sure you're right, why else would
they seal it?

I'm not sure whether the Fuel Injection Limiter has a spring loaded
plunger in it or not. Detroit Diesel engines had a similar device but
in their case it was to limit surge at idle.

Yes, the manual shows a spring in it (though the manual isn't always a
perfect indicator of what is actually installed).

.. The screw should have a
slot so it can be adjusted with a screw driver, if not scratch a line
on the screw so you can tell how far you have turned it.

Right, in practice the nuts and washers are all tight against each
other and no part of the shaft is showing. The adjuster is a hollow
threaded rod with a spring inside of it. The slot on the top of the
rod is the spring retention screw. Not sure if turning it ccw will
undo it or the control shaft. Assuming nothing moves when I take the
acorn I suppose I could make a mark on the shaft w/respect to the lock
nut.

Thanks!

-- Tom.


Update:

When I said to hold the nut when removing the acorn nut I neglected to
say"loosen the nut when adjusting the screw".

Let us know how it works out.

Bruce-in-Bangkok
(correct email address for reply)

On Mar 21, 4:44 pm, Bruce in Bangkok wrote:
... When I said to hold the nut when removing the acorn nut I neglected to
say"loosen the nut when adjusting the screw". ...

Thanks, Bruce. I'll certainly report back if I go for it and I don't
blow myself up...

-- Tom.

On Thu, 20 Mar 2008 14:01:05 -0700 (PDT), "
wrote:

I've got a Yanmar 2gm20 that I'm pretty convinced has a problem with
the governor (speed is not well controlled especially when it comes
under load).

You may get more on-target suggestions if you describe the symptoms
more precisely - such as what load, what rpm variations.

--Vic

On Mar 22, 2:15 am, Vic Smith wrote:
You may get more on-target suggestions if you describe the symptoms
more precisely - such as what load, what rpm variations.

Could be. But in a way I'm trying to avoid doing that because I've
been down that route here and with pros and 100% of people say air in
the fuel. For years I've believed them and labored to get the fuel
system just so and I've spend a lot of money having the pros work it
over, too. It is not a show stopper. I've traveled tens of thousands
of miles with it. But, it is a continual annoyance. So, basically
the last part that nobody has messed with that could reasonably be
causing my problems is the governor. Applying the do the easy stuff
first principle I looked at the beast and it has an adjustment the
might possibly fix or mask the problem and it looks super easy to do.
But, it is factory sealed. So, my question was, in essence, will
vengeful samurai descend from heaven to cause me grave bodily harm if
I tweak that puppy? So far, I think I've gotten a good solid "maybe"
on that. I'm not really asking for a diagnosis of the problem. I
pretty much lost faith in them (though they are always amusing and I'm
happy to read any that are proffered).

-- Tom.