Problem starting Yanmar 2QM20H and white smoke when running - SailNet Community

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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Old 07-29-2010
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Problem starting Yanmar 2QM20H and white smoke when running

Hi

I'm trying to help my father get our Yanmar 2QM20H to start again. It started with that the tank went empty this spring and then there has been no luck since. The feed pump was changed and that helped us to get it to start 3 times after much labor.

Now after lot of bleeding of air we managed to get it started, just. But have to run for some time with start engine and compression release in before it finally kicked in. Then it ran on low rpm 10 of max 25) on full throttle. After some more bleeding of the return line while running the engine it finally revved up to max rpm. We ran it for some 10 minutes on 70% speed, but all the time we got massive amount of white smoke (not water vapor as it was stinging and smelt smoke). Cooling water comes out ok but there is also diesel coming out of the exhaust as we see a growing diesel shine on the surface of the sea around the boat.
When the engine died due to low speed, we could not start it again.

I'm wondering if it is the injector nozzel that has a problem. They have bee overhauled, but not replaced. I took out the two and one had some brunt residue around the pin sticking out, while the other was just wet.

Could it be the case that the one gets high enough temperature while the other doesn't and that there is unspent fuel?

I just hope it is not the HP pump...

Any hints or tips much appreciated!

PS: There is Tall Ships Race in town these days so we are anxious to get the engine running to go out and look at the marvelous ships.
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Old 07-29-2010
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There is a good possibility that when you sucked the tank dry, that the 'last' amount of liquid sucked was WATER. When solid WATER comes in contact with the HOT injector tips ... you can do GREAT DAMAGE to the tips.

Suggest you remove the injectors, and send them out to a local 'injector shop' to have them checked out (repaired or replaced).
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Old 07-29-2010
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Quote:
Originally Posted by RichH View Post
There is a good possibility that when you sucked the tank dry, that the 'last' amount of liquid sucked was WATER. When solid WATER comes in contact with the HOT injector tips ... you can do GREAT DAMAGE to the tips.

Suggest you remove the injectors, and send them out to a local 'injector shop' to have them checked out (repaired or replaced).
I replaced them. Didn't help at all . I noticed on one there was a burnt layer of soot. Quite thick. On the other it was more wet and just a thin layer of soot.

However, after trying a lot I notice that in order to start the engine (very difficult) I need to bleed off diesel from the bolts on top of the injectors that are connected back to the fuel filter. If I get the engine started I get a very low RPM 1000 (out of 2300) even with full throttle. When I open one of the injector tops for a bit, not the line that feeds the injector, the engine picks up speed after a short time to full speed. I cannot maintain it below 700 RPM though, so if I try to put it in forward the engine dies. I have managed to run it in reverse. At low RPMs there is some "hammering" noise from the engine.

I noticed as the engine got hot it was easier to start, but still difficult. Big problem is the white smoke.

The engine is seawater cooled.

I have read that the timing of the diesel injected can be wrong so that there is unspent diesel. Is that something one can adjust or one need a workshop to do it?

Also could the cylinder head gasket have been destroyed?

Last edited by epp; 07-29-2010 at 12:04 PM.
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Old 07-29-2010
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Move the injector timing ahead a degree or two. Locate the arrow showing the direction the pump turns. Loosen the nuts enough that you can then twist the pump in the opposite direction the arrow points...just a little, maybe 2 degrees. Re tighten and see if your problem is gone.

Works for me anyway

But white smoke is the most difficult to diagnose I think, therefore the most difficult to remedy
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Old 07-29-2010
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Quote:
Originally Posted by T37Chef View Post
Move the injector timing ahead a degree or two. Locate the arrow showing the direction the pump turns. Loosen the nuts enough that you can then twist the pump in the opposite direction the arrow points...just a little, maybe 2 degrees. Re tighten and see if your problem is gone.

Works for me anyway

But white smoke is the most difficult to diagnose I think, therefore the most difficult to remedy
Thanks for the tip. I'm quite new to engines (only been working on this engine for a couple of days and done internet searches). Where do I locate the injector timing? Is it inside the injector pump? I just found a service manual for the 2QM15 engine, but haven't found the injector timing yet. Could it also be called something else.

Is it hard to do this by the way. I mean is it easy to break things?
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if you haven't took off/took apart the injection pump i doubt the timing is off.white smoke is usually caused by a bad injector,low injection pressure or low cylinder compression.with the engine running[be very careful not touch moving pulleys or moving parts]loosen each fuel line [one at a time] slightly until you see a little fuel spitting,if that cylinder is firing you will notice a distint difference,if theres no difference that cylinder is not firing and thats your bad injector or cylinder problem[low compression /bad valves etc
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if you can't isolate a cylinder that is not firing its most likely a bad injection pump or clogged lines/filter etc
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you may need to measure the compression,takes a special high compression tester
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Old 07-29-2010
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Quote:
Originally Posted by sawingknots View Post
if you haven't took off/took apart the injection pump i doubt the timing is off.white smoke is usually caused by a bad injector,low injection pressure or low cylinder compression.with the engine running[be very careful not touch moving pulleys or moving parts]loosen each fuel line [one at a time] slightly until you see a little fuel spitting,if that cylinder is firing you will notice a distint difference,if theres no difference that cylinder is not firing and thats your bad injector or cylinder problem[low compression /bad valves etc
Thanks. Will try. The injection pump hasn't been touched. I'll try to see about the cylinder firing.
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Note: the above I wrote was done after having the injectors and injector pump were rebuilt, so I knew it wasn't either of them. Like I said, it worked for me. BTW, I have to give credit to Buddy at Baltimore Diesel for the tip I shared, 50+ years in diesel mechanics, the man is practically a legend, and one of the nicest guys you'll ever meet. Baltimore Diesel Service in Glen Burnie, MD - YellowBot

White smoke seems to be more common boat engines than autos? Dunno really, just my guess, I don't see many trucks going down the road with white smoke pouring out the exhaust like I do see on boats
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