Yanmar wet stacking

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Mikedefieslife

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Anyone had any experience with a Yanmar engine wet stacking (i.e. spitting out semi combusted diesel)?

Last time I ran my engine a month ago all was well. More recently I ran it to find that once I got to 2250-2500 rpm it would spit out large clumps of semi combusted diesel and plumes of dark grey smoke.

I've taken the elbow off and cleaned that out, and around the outlet how from the exhaust manifold. I'm getting plenty of water from the exhaust so I don't believe that are any blockages.

The engine is a Yanmar 3GM30 with a 12837-13550 elbow (which seem more rare then the usual ones with a hose barb on). It starts in about half a turn, and runs sweet up until the aforementioned RPM.
 
I wonder if a 5 or 10 minute burst at full revs might clear it up? Just a thought.

Otherwise I wonder if there's a problem with the injectors? The rev burst might sort that out as well .... otherwise tipping in some decent injector cleaner can't do any harm.

Richard
 
Sounds bad, my guess is an injector problem, or less likely, the HP pump.
If it happens in neutral, you could try running it briefly up to the problem revs with each injector fuel pipe disconnected in turn. (It'll be a bit rough!).
That might indicate if one of the injectors is the culprit.
 
It only happens at higher revs above 2250. This is after a good warm up. Tried it a few days in a row now.

Someone mentioned running it at where the problem occurs then opening the decompression level on each cylinder in turn. I didn't think that sounded healthy, but gave it a go anyway. All it does it make more smoke. As soon as I back off the revs a bit, all is right in the world again.

The injectors are all connected via the same metal fuel line. It's no possible to just unplug one.
 
Mikedefieslife said:
The injectors are all connected via the same metal fuel line.
Click to expand...

If that were the case then they'd all squirt at the same time and the crankshaft wouldn't go round.

Each injector has its own fuel line from the injector pump, and it's perfectly possible (if messy, I assume) to slacken the union on just one of them.

Pete
 
A bit of a wild throught , I seem to remember way back on this forum some had a similar problem and it was the intake filter collapsing with the increased airflow and starving the engine of oxygen

Tross
 
prv said:
If that were the case then they'd all squirt at the same time and the crankshaft wouldn't go round.

Each injector has its own fuel line from the injector pump, and it's perfectly possible (if messy, I assume) to slacken the union on just one of them.

Pete
Click to expand...

He's a picture of the rusty mess otherwise known as my Yanmar 3GM30.

You can see left to right that a HP fuel line enters the first injector the others are all connected to it by a metal fuel line.

IMG_2466.jpg

Anyway, this might all be much ado about nothing. I've been told that 2500rpm while tied to the dock might just be putting too much load on the engine, hence the mess.

I have seen others do it here in the marina, but they have had more powerful engines.
 
Mikedefieslife said:
He's a picture of the rusty mess otherwise known as my Yanmar 3GM30.

You can see left to right that a HP fuel line enters the first injector the others are all connected to it by a metal fuel line.

View attachment 68486

Anyway, this might all be much ado about nothing. I've been told that 2500rpm while tied to the dock might just be putting too much load on the engine, hence the mess.

I have seen others do it here in the marina, but they have had more powerful engines.
Click to expand...
Your original symptoms are exactly what you would expect from over propping - that is putting too much load on the engine so that it cannot burn the fuel that is being injected. You are reproducing this condition by trying to get full revs while tied up.

Take the boat out (if you can) and once up to temperature give it 10-15 minutes at the maximum revs it can achieve, which should be at least 3400.
 
Mikedefieslife said:
He's a picture of the rusty mess otherwise known as my Yanmar 3GM30.

You can see left to right that a HP fuel line enters the first injector the others are all connected to it by a metal fuel line.

View attachment 68486
Click to expand...
The metal pipe running between the injectors is the fuel return or spill-off line. When there’s more fuel supplied than the injector needs, there has to be somewhere for it to go. The flexible hose on the left takes the excess fuel back to the low pressure side of the fuel system, in some cases straight back to the tank. The high pressure supply to each injector comes from the distribution pump, you can see the pipe for the middle injector in your photo.
 
Doh. So basically I created a problem that isn't a problem. haha. I just don't remember any unburnt diesel last time I ran the engine, but perhaps I didn't push past 2000 rpm. Bearing in mind the redline is some 3600.

At least that is potentially out of the way, and I've cleaned the exhaust elbow and replaced some of the electrical wiring now. Still plenty to clean up and check and repaint around there, but one step at a time.

It really is a rather crude system compared to EFI petrol engines I'm used to working on.

p.s. I found the injector lines. ;)
 
I would get the injectors out and get them tested and serviced. I've just did it on my 2gm20. Cost me all of £12 plus a couple if pounds for sealing rings. It could also be your injection timing thats out or valve clearance adjustment. I found a few useful videos on you tube, search yanmar 2gm.
 
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