Yanmar 6LYM-UTE smoking

jplob96

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I have a 1995 Yanmar 6LYM-UTE Ser #40489 with 2600 hours. In early spring and late fall when air temp is below 40 degrees, the engine on a cold start exhaust a lot of white smoke and some raw fuel. The smoke is so bad it fogs out the marina. This last about 10 minutes and gets better the longer the engine runs. When at normal operating temp. smoke is gone. Engine is a little hard to start and runs rough for about a minute or two. During the summer the engine fine, still smokes some, but nothing like when it is cold outside. Mack Boring Rep said injectors may need cleaning. I had that done 400 hours ago and saw no difference. He also said that the air heater system may not be functioning properly. Do not know what that is, there is a air cooler on this engine. ANY THOUGHTS ?? PS: I burn #2 home heating oil with an additive.
 

djmarchand

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The air heater is a couple of electric coils on the intake manifold of the engine. They come on (and pull about 80 amps) during the first 3-4 minutes of running and help with smoke.

But it sounds like you have more than normal smoke. Also you say the engine is hard to start when cold. It should start within 2-3 seconds at 40 deg outside air temp.

Hard starting and smoke could be injectors. But it could also be low compression. One quick check is to put your hand behind the black tube on the starboard aft end that terminates on top of the air cleaner. At cruising rpm can you feel significant blowby? That is caused by failing rings which will also cause hard starting due to low compression.

Also ask this question on boatdiesel. There are some real marine engine pros there.

David
 

jplob96

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David, Can't find any electrical coils on engine. I have a operation manual that has instructions for starting in cold weather. It says " Turn off boost compensator" I don't know how to do this. Next "Pull the low temp starter knob all the way to the initial position. The boost compensator will automatically be activated after starting the engine" Use only when start up of engine is not easy" Return knob to normal position.
 

djmarchand

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My engine is the Yanmar 6LY STP 370 hp version which I thought was similar to the UTE engine, but maybe not.

The electrical terminals to the heater coils are shown in the attached picture and are just in front of the oil filter and to the port of the label.

If you have them and they are working, watch your voltmeter just after you start the engine. The voltage will drop below 12V for 3-4 minutes until a timer or temp sensor turns them off. Then the voltage will rise to 13 or so.

I don't know what a boost compensator is and I am sure I don't have a low temperature starting knob. I advance the throttle an inch or so and it starts within two seconds even below 40 degrees.

Some engines go to full fueling (for cold starting) if the throttle is advanced a little, others if the throttle is all of the way forward.

When you crank it and it isn't starting, do you get clouds of white smoke out of the exhaust. That is a good indication that you are getting fuel but it isn't burning enough to start the engine.

BTW the blowby tube is in the bottom of the pic. The hose continues out of the frame to the right from the tee and stops just over the air cleaner. Check that hose for significant blowby. If you get heavy air pulses from the hose under load then you may have excessive blowby.

Yanmar 6LY Heater Elements.jpg
 

jplob96

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My oil filter goes the opposite way, towards the front of the engine and over the air cooler. Did not know what I was really looking for, the heater coils may be there. I don't know if white smoke is coming out the exhaust while cranking,never looked back until engine started. takes about 5 to7 seconds to start, then runs rough for about a minute like it's not burning all the fuel. There is raw fuel coming out the exhaust, you can see it on the water. You mentioned a air cleaner, is this the foam filter over the turbo intake?
 

djmarchand

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Yes, the air cleaner is the foam filter.

5-7 seconds sounds like a long time to crank. It could be a fuel system air leak. That is why I asked what happened when cranking. If you get clouds of smoke while cranking, then it is unlikely to be a fuel problem. But if the exhaust is pretty clear while cranking and then it suddenly fires, that means it is a fuel problem.

You might want to post your problem over on boatdiesel.com. There are some real pros there who may be able to help and should know more about your specific engine.

David
 

jojobee

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This is typical. We always told people to start the engine, get the dock line and go. Adding a cetane improver in the fall/winter helps out. A valve adjustment would not hurt either if you have not had one in a while.
 

captainlarry84

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Smoking with this excellent motor is something you have to live with. That is one of the main reasons why Yanmar had to drop from its line as they could not get it to meet tier regs.
A block heat will help on the cold morning starts along with quality fuel & a booster. So don't waste your money on injectors.
 

jplob96

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captainlarry84, Sounds like you do not approve of burning home heating oil. I use DieselKleen as an additive. Can you recommend an additive that might be better? Also this engine has a pull cable that actuates a lever on the top of the injection pump. Book says to use when starting in cold weather. Are you familiar with this?
 

captainlarry84

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captainlarry84, Sounds like you do not approve of burning home heating oil. I use DieselKleen as an additive. Can you recommend an additive that might be better? Also this engine has a pull cable that actuates a lever on the top of the injection pump. Book says to use when starting in cold weather. Are you familiar with this?
#2 is fine for the older diesels but this new high performance sewing machines need the good stuff. As far as additives go this is the one that Yanmar recommends. Mac Boring sell it. http://www.fppf.com/
 
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jplob96

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captainlarry84, This engine is a 1995 model, 3200 rpm max. Do you consider this a older engine?
 

05bill

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additive

use good fuel, and add stynadyne see what happens
 
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