Anyone know anything about unsticking a diesel engine governor?

[Chris Green]

Our boat in France has an ancient (1950s/1960s) Mercedes OM312 engine.

We recently went out to the boat for the first time in 18 months (due
to Covid etc.). Much to our surprise while it was dirty outside and
needed a thorough clean it was mostly OK. In particular the solar
panels have kept both Leisure and Starter batteries in good condition.

The engine even started fairly easily but immediately tried to rev
itself to pieces so I had to close it down immediately. I tried a few
more times but it did just the same.

So, presumably, the governor has got stuck. Does anyone here know
if likely failure modes? I'm pretty sure it's a centrifugal governor
and I do have a manual for the engine but if I can go back with a few
pointers it would be helpful.

[Martin Nicholas]

On Fri, 17 Sep 2021 17:56:28 +0100

Post by Chris Green
Our boat in France has an ancient (1950s/1960s) Mercedes OM312 engine.
We recently went out to the boat for the first time in 18 months (due
to Covid etc.). Much to our surprise while it was dirty outside and
needed a thorough clean it was mostly OK. In particular the solar
panels have kept both Leisure and Starter batteries in good condition.
The engine even started fairly easily but immediately tried to rev
itself to pieces so I had to close it down immediately. I tried a few
more times but it did just the same.
So, presumably, the governor has got stuck. Does anyone here know
if likely failure modes? I'm pretty sure it's a centrifugal governor
and I do have a manual for the engine but if I can go back with a few
pointers it would be helpful.

Try asking on canalworld[dot]net. Numerous engine people there.

[Chris Green]

Post by Martin Nicholas
On Fri, 17 Sep 2021 17:56:28 +0100

Post by Chris Green
Our boat in France has an ancient (1950s/1960s) Mercedes OM312 engine.
We recently went out to the boat for the first time in 18 months (due
to Covid etc.). Much to our surprise while it was dirty outside and
needed a thorough clean it was mostly OK. In particular the solar
panels have kept both Leisure and Starter batteries in good condition.
The engine even started fairly easily but immediately tried to rev
itself to pieces so I had to close it down immediately. I tried a few
more times but it did just the same.
So, presumably, the governor has got stuck. Does anyone here know
if likely failure modes? I'm pretty sure it's a centrifugal governor
and I do have a manual for the engine but if I can go back with a few
pointers it would be helpful.

Try asking on canalworld[dot]net. Numerous engine people there.

OK, thanks, I'll try that.

[John Williamson]

Post by Chris Green
Our boat in France has an ancient (1950s/1960s) Mercedes OM312 engine.
We recently went out to the boat for the first time in 18 months (due
to Covid etc.). Much to our surprise while it was dirty outside and
needed a thorough clean it was mostly OK. In particular the solar
panels have kept both Leisure and Starter batteries in good condition.
The engine even started fairly easily but immediately tried to rev
itself to pieces so I had to close it down immediately. I tried a few
more times but it did just the same.
So, presumably, the governor has got stuck. Does anyone here know
if likely failure modes? I'm pretty sure it's a centrifugal governor
and I do have a manual for the engine but if I can go back with a few
pointers it would be helpful.

The classic first thing to do is tap the injector pump near the throttle
lever or, if your can identify where it is, the govermor wiv a nammer....

NOT a metal faced one, but a soft faced one. If you don't have a soft
'ammer, 'ittin' a block of wood wiv a normal 'ammer is just as good.

If that doesn't work, then it needs to come off and be serviced.

The moving parts that control the injection amount are built to very
precise tolerances, so a tiny bit of stiction from old oil or
condensation can stop them moving, and the shock from a hammer can often
free them up for many years of normal service.

[Chris Green]

Post by John Williamson

Post by Chris Green
Our boat in France has an ancient (1950s/1960s) Mercedes OM312 engine.
We recently went out to the boat for the first time in 18 months (due
to Covid etc.). Much to our surprise while it was dirty outside and
needed a thorough clean it was mostly OK. In particular the solar
panels have kept both Leisure and Starter batteries in good condition.
The engine even started fairly easily but immediately tried to rev
itself to pieces so I had to close it down immediately. I tried a few
more times but it did just the same.
So, presumably, the governor has got stuck. Does anyone here know
if likely failure modes? I'm pretty sure it's a centrifugal governor
and I do have a manual for the engine but if I can go back with a few
pointers it would be helpful.

The classic first thing to do is tap the injector pump near the throttle
lever or, if your can identify where it is, the govermor wiv a nammer....
NOT a metal faced one, but a soft faced one. If you don't have a soft
'ammer, 'ittin' a block of wood wiv a normal 'ammer is just as good.
If that doesn't work, then it needs to come off and be serviced.
The moving parts that control the injection amount are built to very
precise tolerances, so a tiny bit of stiction from old oil or
condensation can stop them moving, and the shock from a hammer can often
free them up for many years of normal service.

Yes, that does sound like a good thing to try initially anyway. :-)

I have found a very short section in the manual I have that refers to
the governor:-

A centrifugal governor adapted to the intended use of the engine
is flanged onto the injection pump.

With the variable speed controller, any desired speed can be set
within the speed range can be set. The controller maintains this
speed regardless of the load constant. (Use e.g. for pump drive.)

The idle final speed controller prevents the speed from falling
below a minimum and exceeding the specified maximum speed. With a
regulating lever the power of the motor can be adapted to the load
(use e.g. in Vehicles).

End controllers are used for motors that only run at a certain,
fixed speed and must keep this speed between zero load and full
load (e.g. generator sets).

... and for maintenance:-

Oil the Kenuliergnatänge, check for the largest flow rate at the
stop, evil. readjust

Oil the ball heads and bearing points of the levers. The linkage
must not jam. When the regulating lever is in full load position,
the filling lever on the injection pump against the stop. If
necessary, linkage with turnbuckle or readjust on the ball heads.

I think the maintenance bit has lost something in the tranlation! :-)

[John Williamson]

Post by Chris Green
I think the maintenance bit has lost something in the tranlation! :-)

Better than Chinglish. ;-)

Standard layout for the period. The centrifugal governor mechanically
moves a rack inside the injector pump, which moves levers or gears on
the flow control valves in the high pressure pumps (One per injector).

When the engine starts, the rack is set to give full flow at the
injectors, and as it speeds up, it reduces the flow until the diesel
flow matches the power being drawn by the load.

Stiffness in the governor/ rack mechanism can cause symptoms ranging
from non starting to unwanted shutdown to hunting to full on flat out
running.

Another thing you might want to check is that the oil level in the
injector pump is correct and the oil is in good condition (Usually a
plug in the side of the pump body for filling and level checking, with
another to drain it, and that there is no diesel in the engine oil
(Unlikely to be much if any, as the engine stop still works.).

[Chris Green]

Post by John Williamson

Post by Chris Green
I think the maintenance bit has lost something in the tranlation! :-)

Better than Chinglish. ;-)

Possibly.

Post by John Williamson
Standard layout for the period. The centrifugal governor mechanically
moves a rack inside the injector pump, which moves levers or gears on
the flow control valves in the high pressure pumps (One per injector).
When the engine starts, the rack is set to give full flow at the
injectors, and as it speeds up, it reduces the flow until the diesel
flow matches the power being drawn by the load.
Stiffness in the governor/ rack mechanism can cause symptoms ranging
from non starting to unwanted shutdown to hunting to full on flat out
running.
Another thing you might want to check is that the oil level in the
injector pump is correct and the oil is in good condition (Usually a
plug in the side of the pump body for filling and level checking, with
another to drain it, and that there is no diesel in the engine oil
(Unlikely to be much if any, as the engine stop still works.).

Thanks, all useful. I'll have some sort of idea what I'm looking for
to unsieze. I hadn't realised (and, from the manual I think there is)
that there is a special oil sump for the injector pump. That will be
an obvious first thing to check out.

[Chris Green]

Well it turned out to be dead simple to fix.

I squirted some penetrating oil into the little flap oil filler for
the governor and, a little later, filled it up to the correct mark on
its dipstick. (Yes, there's a dipstick for the governor!).

I also topped up the injector pump oil, that too has its own dispstick.

.... and all is well, started engine and it didn't race off and
settled down to ticking over at 700rpm. It all sounds very sweet now.

I just need to remember there are *three* dipsticks to check (plus the
one on the drive gearbox).

[John Williamson]

Post by Chris Green
Well it turned out to be dead simple to fix.
I squirted some penetrating oil into the little flap oil filler for
the governor and, a little later, filled it up to the correct mark on
its dipstick. (Yes, there's a dipstick for the governor!).
I also topped up the injector pump oil, that too has its own dispstick.
.... and all is well, started engine and it didn't race off and
settled down to ticking over at 700rpm. It all sounds very sweet now.
I just need to remember there are *three* dipsticks to check (plus the
one on the drive gearbox).

<Grin> Glad that it was the simple problem. Computers, who needs 'em?