Diesel Newbie

[winston1]

I'm not a diesel engineer but I recall the 3gm had a mechanical fuel pump as it was possible to run the engine with no battery (if memory serves). I think the old Saab one lunger was like that too.

I'm certainly not a diesel engineer either and not familiar with the 3gm or Saab. I do think most of the Yanmars talked about on this forum will run without a battery too. Course you have to get them cranked.

 

[Gary Sweat]

I'm certainly not a diesel engineer either and not familiar with the 3gm or Saab. I do think most of the Yanmars talked about on this forum will run without a battery too. Course you have to get them cranked.

When I had a weak alternator, I would start the tractor and then turn off the key. Worked just fine but the flip side is you won't have any idiot lights to tell you if the oil pressure drops or it is overheating. Another reason for gauges I guess. On the older diesels you don't need the electrical system to run them.

 

[normde2001]

Interesting as the only way to stop the Yanmar 3GM marine engine was through decompression. I don't see how it would be harmful as it simply prevents combustion.

It was also possible to use the decompression levers independently so with a weak battery or manual crank you could get some momentum on the flywheel and then compress only one cylinder to get the motor running.

I seriously doubt that. This is directly from the 1GM10 ops manual, which is, no doubt, similar to the 3GM30. I'm sure the engine stop cable engages a fuel shut-off solenoid, as in other Yanmar engines.

SHUTTING DOWN THE
ENGINE​

NOTICE:​

​

​

​

NEVER stop the engine
abruptly during operation. Yanmar
recommends that when shutting the
engine down, allow the engine to run,
without load, for 5 minutes. This will
allow the engine components that
operate at high temperatures, such as
the exhaust system, to cool slightly
before the engine itself is shut down.​

1. Reduce the engine speed to low idle
and put the shift control lever in
NEUTRAL.
2. Accelerate from low speed to high
speed and repeat five times. This will
clean out the carbon from the cylinders
and the fuel injection nozzles.
3. Allow the engine to run at low speed
(approximately 1000 rpm) without load
for five minutes.
4. With the key in the ON position, pull and
hold the engine stop knob​

(Figure 5, (1))​

​

​

​

​

until the engine has
come to a complete stop. After the
engine has stopped, turn the key switch
to OFF.​

Note: Continue to hold the engine
stop knob until the engine is
completely stopped. If the knob is
released before the engine has
completely stopped, it may restart.​

(3)
(1) (2)​

0005842​

Figure 5​

1 Engine Stop Knob
2 Bulkhead
3 Control Cable​

5. Turn off the master battery switch (if
equipped).
6. Remove the key.
7. Close the fuel cock.
8. Close the seacock (if equipped).​

NOTICE:​

​

​

​

Be sure to close the
seacock. Neglecting to close the
seacock could allow water to leak
into the boat and may cause it to
sink.​

Note: The engine may be stopped by raising
the decompression lever, but avoid doing so
except in times of emergency. The
decompression lever releases compression
pressure in the cylinder which causes the
engine to stop. However, fuel injection does
not stop and fuel continues to be pumped
into the cylinder. This can lead to abnormal
combustion when the engine is restarted
and is not desirable.​

ENGINE OPERATION​

38

 

[jonyyuma]

Wow, Marine directions,,,Never have read the part about racing the engine several times to decarbon the injectors and cylinders. I guess this is for long idling periods, or continuous operation at one speed , as in trolling, or dragging a net?? Interesting??

I seriously doubt that. This is directly from the 1GM10 ops manual, which is, no doubt, similar to the 3GM30. I'm sure the engine stop cable engages a fuel shut-off solenoid, as in other Yanmar engines.

SHUTTING DOWN THE
ENGINE​

NOTICE:​

​

​

​

NEVER stop the engine
abruptly during operation. Yanmar
recommends that when shutting the
engine down, allow the engine to run,
without load, for 5 minutes. This will
allow the engine components that
operate at high temperatures, such as
the exhaust system, to cool slightly
before the engine itself is shut down.​

1. Reduce the engine speed to low idle
and put the shift control lever in
NEUTRAL.
2. Accelerate from low speed to high
speed and repeat five times. This will
clean out the carbon from the cylinders
and the fuel injection nozzles.
3. Allow the engine to run at low speed
(approximately 1000 rpm) without load
for five minutes.
4. With the key in the ON position, pull and
hold the engine stop knob​

(Figure 5, (1))​

​

​

​

​

until the engine has
come to a complete stop. After the
engine has stopped, turn the key switch
to OFF.​

Note: Continue to hold the engine
stop knob until the engine is
completely stopped. If the knob is
released before the engine has
completely stopped, it may restart.​

(3)
(1) (2)​

0005842​

Figure 5​

1 Engine Stop Knob
2 Bulkhead
3 Control Cable​

5. Turn off the master battery switch (if
equipped).
6. Remove the key.
7. Close the fuel cock.
8. Close the seacock (if equipped).​

NOTICE:​

​

​

​

Be sure to close the
seacock. Neglecting to close the
seacock could allow water to leak
into the boat and may cause it to
sink.​

Note: The engine may be stopped by raising
the decompression lever, but avoid doing so
except in times of emergency. The
decompression lever releases compression
pressure in the cylinder which causes the
engine to stop. However, fuel injection does
not stop and fuel continues to be pumped
into the cylinder. This can lead to abnormal
combustion when the engine is restarted
and is not desirable.​

ENGINE OPERATION​

38

 

[Semper Fly]

WOW! Interesting how a simple question can elicit such a variety of responses.:laughing:

 

[California]

WOW! Interesting how a simple question can elicit such a variety of responses.

That's why I find this group interesting. I learn something every time.

Thanks Norm for finding that.

Anybody know if we should do this 'accelerate five times to blow out the carbon' ritual before shutdown too?

 

[jonyyuma]

If you had that much carbon, then I am sure some of it would come loose with an attempt. My tractor does not seem to blow much up the exhaust except heat. I have seen huge carbon {soot} balls come from big cummins truck engines , after sitting a spell. Myself I will continue to let it cool down, then pull the fuel cut-off. That is until, I read something better. Jy.

 

[IslandTractor]

I seriously doubt that......

Note: The engine may be stopped by raising
the decompression lever, but avoid doing so
except in times of emergency. The
decompression lever releases compression
pressure in the cylinder which causes the
engine to stop. However, fuel injection does
not stop and fuel continues to be pumped
into the cylinder. This can lead to abnormal
combustion when the engine is restarted
and is not desirable.
ENGINE OPERATION
38

You are correct. I think I was mistaken in thinking that the stop engine cable, which is clearly mechanical, was causing decompression. I know that shutting off the key on these engines did not stop the engine but as you pointed out, the engine stop cable must stop the mechanical fuel pump rather than causing decompression.