On Mar 20, 9:46 pm, Bruce in Bangkok wrote:
... First of all, the word "limiter" is a bit confusing. It may be a
"Yanmar" word but it is not a word normally associated with diesel
engines except in the sense of a RPM limiter which usually implies a
device to limit the maximum RPM - a safety devise in other words -
which is not a part that Yanmar uses on the 2GM20.

Well, I'm not even to the point where I can pretend to be clued in
here so I'm just using the terminology out of the manual. The
governor has three externally adjustable controls: "Injection
Limiter", "no-load maximum speed limiter", and "idling adjuster". I'm
familiar with the idling adjuster and it's trivial to work with. The
no-load maximum speed limiter is sealed at the factory and seems to be
correct. So, I'm thinking of messing with the injection limiter. It
is essentially the end stop for the fuel control lever on the
injection pump and limits the total amount of fuel that the governor
can demand. The manual says " if the engine does not accelerate
smoothly (ie. speed is not well controlled), turn the limiter slightly
counter-clockwise. Note: if it is turned back too much, it will
produce exhaust smoke." Black smoke I can deal with. Thrown rods
would suck. Since they do seal the injection limiter at the factory
I'm taking your warning seriously, but it isn't what I want to
hear...

Further, adjusting the stops for the fuel lever won't effect anything
except the RPM settings because there is no direct connection between
the fuel lever and the injection pump. It only compresses a spring
that works against the governor.

Right, the part I'm looking at prohibits the governor from opening the
fuel pump beyond a certain point (a slightly fuzzy point as it has a
spring in it too). It is not a speed control at all.

Can you give a better description of the problem? For example, does
the engine accelerate normally when in neutral?

Generally, yes, though when the high output alternator kicks with a
big load the engine falls back to idle speed.

Does the engine run
rough while accelerating?

No, it runs very smoothly.

Does it only happen with the engine in
forward or reverse?

Both and neutral.


Does the engine vibrate more then normal when it
is doing whatever it is doing?

No.

Are you jamming the throttle from idle
to wide open very rapidly?

No, and if demand comes onto the engine when it is stable in high idle
it will loose rpms.

Upon acceleration does the engine
momentarily over speed and then settle back to the selected RPM?

No, never. Indeed, it tends to not reach speed so that I have to over
throttle a bit to get the desired rpms and then back down to keep them
steady. It is not lash in the morse cable.

The problem seems most marked when the motor is cold, but as the
batteries demand drops I'm asking the engine to produce less torque
after it has run for a while and even when the batteries are topped
off it still tends not to reach the demanded rpms. I have noticed
that this engine uses less fuel than its counterpart when running at
speed even when the nominal rpms are even. I am certainly confused.
But like I say I've had the pros go over it and they've been unable to
fix it. We've gone over the fuel system multiple times except that I
haven't had the injection pump out and I haven't messed with the
injection limiter. It may be that the injection pump is mis-shimmed
and thus the timing is out but getting the pump off is a major PIA
with this installation. The limiter I can get at so it tempts me...

-- Tom.