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Old 09-03-2015, 03:35   #61
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Re: Yanmar diesel smoking/ black soot

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Originally Posted by Bronk33 View Post
Thats the thing...mine starts up right away...cold or hot. And will stay running.
Why would the smoke go away after it's been running for 10 mins at 2500-3000rpm?



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Because, your engine stays into cold start mode.

In a cold start mode, you want an air/fuel ratio with more fuel than air.
you have either two ways to achieve this.
-either you inject more Diesel or Gas (works the same on a petrol engine)
- either you restrict air intake ( a choke on a carb engine).

Early days injection systems used a mecanical system (kinda hot wire driven) to restrict air intake or a dedicated cold start injector.

Either system were triggered by a heat sensor checking water coolant temperature.

As long as the temperature as not reached a set temp, engine stays in cold start mode.

Modern injection systems with CPU which could monitor a temperature sender allowed to get rid of the mecanical or cold start injector.
(saving money).

As long as the CPU receives an information that the ideal temp is not reached it increases the opening time of the injectors to inject more fuel....resulting in soot.

You have said it yourself " power not strong = wrong air fuel ratio.

you mentionned also :
" motor slow to decelerate and shut down".
Think of a gas engine carbureted with a choke jammed in a shut down position (therefore cold start).
You get the same symptoms.

I would definetly start checking temperature sender(s) to start with.

Either this sender deliver an incorrect Temperature value to the CPU because it is faulty, or it sends a correct information about a coolant temperature which never reaches its ideal temp due to a thermostat jammed in an open position (which is quite rare, most of a time a faulty thermostat stays stuck in a close position).
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Old 09-03-2015, 03:53   #62
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Re: Yanmar diesel smoking/ black soot

The OP has a Yanmar 3GMD, this engine doesn't have a CPU. In fact CPUs weren't even available to anyone outside an IBM mainframe when this engine was manufactured.
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Old 09-03-2015, 03:56   #63
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Re: Yanmar diesel smoking/ black soot

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The OP has a Yanmar 3GMD, this engine doesn't have a CPU. In fact CPUs weren't even available to anyone outside an IBM mainframe when this engine was manufactured.
Then, it is a mecanical system which drives the "Cold start mode".

Everything described makes me think of an engine running stucked in mode " cold start".
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Old 09-03-2015, 04:03   #64
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Re: Yanmar diesel smoking/ black soot

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Originally Posted by Claude_Marie View Post
Then, it is a mecanical system which drives the "Cold start mode".

Everything described makes me think of an engine running stucked in mode " cold start".
Well you may be correct although I doubt it. The later variant of this motor, the 3GM30 does not have "cold start" features - mechanical or otherwise; it is unlikely the earlier design was more sophisticated.
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Old 09-03-2015, 04:50   #65
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Re: Yanmar diesel smoking/ black soot

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Well you may be correct although I doubt it. The later variant of this motor, the 3GM30 does not have "cold start" features - mechanical or otherwise; it is unlikely the earlier design was more sophisticated.
Just trying to help (and learn) with fresh knowledge based on my Diesel training course.
;-)
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Old 09-03-2015, 04:55   #66
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Re: Yanmar diesel smoking/ black soot

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Originally Posted by Claude_Marie View Post
Just trying to help (and learn) with fresh knowledge based on my Diesel training course.
;-)
Well you helped me

I didn't know anything about the electronic fuel control of the modern diesel and now I know a bit more, so thanks.
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Old 09-03-2015, 05:34   #67
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Re: Yanmar diesel smoking/ black soot

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Well you helped me

I didn't know anything about the electronic fuel control of the modern diesel and now I know a bit more, so thanks.
Not at all, YOU have helped me to stay away from "old school" diesel engines, thanks.

Not surprisingly modern days training focus on Electronic Fuel Injection systems and trouble shooting associated.
Useless with old engines.
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Old 09-03-2015, 12:06   #68
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Re: Yanmar diesel smoking/ black soot

Start with a compression check, all cylinders.
They may be scored, loss of compression psi.


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Old 09-03-2015, 13:04   #69
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Re: Yanmar diesel smoking/ black soot

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Originally Posted by Boatyarddog View Post
Start with a compression check, all cylinders.
They may be scored, loss of compression psi.


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I would skip doing a compression test unless you just want to work and have the necessary tools laying around. You don't loose compression it goes into the crankcase when rings or valve guides are worn. If when running it blows the dipstick out or if you remove the oil fill cap and it is blowing out oil it's ready to rebuild or replace. If none of this is happening your compression isn't your problem. SC touched on the possibility of over fueling this is possible but would be very low on the list to check unless you have other fuel or govenor problems. Having already switched out the injectors (did anything at all change after this fix?) and no turbo give a close look at the air intake and excessive load possibilities. Good luck


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Old 09-03-2015, 14:11   #70
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Re: Yanmar diesel smoking/ black soot

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There are no o-rings in the yanmar 3gm injectors, just shims and springs. Same really with the injector pump. The only oring on the pump is sealing the top part nut to the injector body and probably would not cause the smoking.

Here's a test, with the engine idling, pull each decompression lever one at the time and see if the black smoke changes to grey or goes away. If it changes you know that the problem is one injector assembly.

I'm pondering if one or more springs that control the governor tension changed temper and got a little weak.

That the engine starts right up means timing and compression are good.

Hum another test.

Remove the acorn cap over the injector limiter, on the front of the engine. Mark with a black marker the position of the injector limitor stud to the case. Now loosen the lock nut (big nut against the cover, not the small nut at the end of the stud), and turn the injector limiter 1/4 turn clockwise, tighten the long nut and start the engine and see if the smoke is better. If better, repeat 1/4 turn adjustment till smoke is gone.

Note: improper adjustment of the injector limiter can damage the engine. But as your already have excessive smoke, that to me means your getting too much fuel to the cylinders. The injector limiter adjusts that.

If no change is noted, return the injector limiter to the original mark and retighten the lock nut and acorn nut.

It's possible the little roller bearing plate between the governer and crankshaft, lost it's bearings, which would cause excessive fuel input. All that and the springs are access by removing the timing cover, which is easy after the crank pulley is removed, which is not easy. If one of the springs on the governor, lost temper that would cause black smoke too. Adjusting the injector limitor would adjust the temper loss out.

I ran the motor and pulled each decompression level.
When I pulled number one smoke turned from black to white.
Pulling #2 and #3 there was no change.


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Old 09-03-2015, 14:23   #71
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Re: Yanmar diesel smoking/ black soot

So it looks like you have a bad injector on number 1.
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Old 09-03-2015, 14:29   #72
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Re: Yanmar diesel smoking/ black soot

Yep that's your problem cylinder, white smoke is of course un-combusted fuel, black is incomplete combustion, but it's being overfueled either injector or could be pump.
I'd swap injectors with another one, if it's the injector the problem will go with the injector.


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Old 09-03-2015, 14:39   #73
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Re: Yanmar diesel smoking/ black soot

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Yep that's your problem cylinder, white smoke is of course un-combusted fuel, black is incomplete combustion, but it's being overfueled either injector or could be pump.
I'd swap injectors with another one, if it's the injector the problem will go with the injector.


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That's the thing. These injectors are brand new.
I suppose I can swap 2 with each other and pull decompression level.
I'm thinking it's either timing or something wrong in pump


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Old 09-03-2015, 14:51   #74
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Re: Yanmar diesel smoking/ black soot

Can't be timing or all three would be off,
Your overfueling the cylinder, and the reason the engine doesn't simply accelerate is because your only overfueling the one. Pretty much has to either be a bad injector or bad pump. I bet pump, but before I spent all that money, I would swap injectors to see if the problem went with the injector as that isn't all that hard to do.


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Old 09-03-2015, 14:52   #75
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Re: Yanmar diesel smoking/ black soot

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Can't be timing or all three would be off,
Your overfueling the cylinder, and the reason the engine doesn't simply accelerate is because your only overfueling the one. Pretty much has to either be a bad injector or bad pump. I bet pump, but before I spent all that money, I would swap injectors to see if the problem went with the injector as that isn't all that hard to do.


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How much is it to have a pump repaired? I know new, they are like $1200


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