Yanmar 2gm Fuel Injection Adjustment Screw broken off / missing - Low compression

[tllong]

Hello,

I recently purchased a sailboat with a Yanmar 2gm that has issues.

Issues:

1. Very low compression in cylinder 2 (cylinder closest to belts/ engine label and farthest from transmission) as indicated in Yanmar manual) -> engine will not start unless cylinder 2 decompression lever pulled back. While the engine is running, when i lower the cylinder 2 decompression lever, there is a clanking noise coming from that cylinder and the engine runs very rough. White smoke is coming from cylinder 2.

2. Oil becomes thin after fresh oil added and runs for a while. (I think this is a blown head gasket)

3. The fuel injection adjustment screw is broken off (see photos)

I have the complete top end rebuild kit and manual. I am planning to do the top end rebuild. (Lots of videos online)

My question is: What should I do about the broken off fuel injection pump adjustment screw?

I can see white smoke being ejected from the hole where this screw broke off while i am running the engine with cylinder 2 compression lever down/ compressed. I suspect that this is leaking air and adding to compression issues.

Should i just replace the entire fuel injection pump?

So far, I have adjusted valve lash to spec and changed oil several times. Cylinder 1 (closest to transmission seems to run fine).

Please help.

[tllong]

This is the what is broken/ missing on my engine ^ see linked image

All that is left is the “injection control shaft” (which looks like the end is snapped off) and the “lock nut” as seen in the attached photo..

Does anyone know where I can get a replacement “Injection Limiter” for a Yanmar 2gm?

[skipperpete]

You can buy the limiter as a Yanmar spare part but brace yourself , it won’t be inexpensive. You might be able to get a second hand one though...... try Minards Diesel if you’re in Australia
The clanking noise and rough running is a far more important issue , you urgently need to deal with that. You will know a lot more once you get the cylinder head off.
Buying a new injection pump will serve no useful purpose, they don’t come with that limiter assembly and if there happens to be a problem with the existing pump it would be easier to get it repaired by a fuel injection tech........ get the injectors pop tested as well.

[Compass790]

skipperpete has given you good advice as always.
Don't know where in the world you are but here you could get a whole used 2GM engine for less than a new injection pump. I would investigate what it needs for rebuild. Here in NZ the Yanmar mafia wanted $630 for a new conrod for our Yanmar YSM8. I saw a complete good runner YSM8 go for $300.
Try & find out if your engine has a tractor equivalent on forums or fbook as parts can be waay cheaper.

New injection pump was about the same price as a conrod.

Your oil could be getting thin from the diesel getting squirted into the cylinder thats not firing.

+1 for urgently stripping it. Dont run it as you will probably do further damage.
If your injection pump limiter works the same way as our YSM8's does it just acts on the end of the fuel rack. i.e. it has no path to the internals of the injection pump so shouldnt allow any air in there.


Again 1st step is to deal with the low compression.
Hope this helps.

[bailsout]

What year is that engine? No horsepower rating. I’ve had a 2QM15 and currently have a 2GM20F. How many hours on it?

[MikeHoncho]

Don’t these allow diesel into the crank if the mechanical fuel pump diaphragm goes south?

[skipperpete]

Originally Posted by bailsout

What year is that engine? No horsepower rating. I’ve had a 2QM15 and currently have a 2GM20F. How many hours on it?

From the i.d plate in the pics, 13hp. 1980-83. After 1983 they went to 20 hp.

[Wotname]

Originally Posted by skipperpete

From the i.d plate in the pics, 13hp. 1980-83. After 1983 they went to 20 hp.

and changed the model descriptor to 2GM20.

[sinnerman]

"If the oil is "thinning out" I would suspect a leaking diaphragm on the mechanical lift pump allowing diesel into the crankcase. This would show up also as the oil level increasing over time. Another possibility is fuel leaking from the injector pump.

DO not use the decompression levers when the engine is running. These are for starting an engine with a low battery.

[tllong]

Thank you to everyone who has responded!

I was able to find the fuel injection limiter: Tom at Certified Diesel and Marine in Engelwood,FL found the part(s) and is a great resource for Yanmar parts!

Before I get too far into taking apart everything on the engine and replacing parts, here is a video of the knock coming from cylinder 2. There is white smoke and diesel coming out of the exhaust when cylinder 2 compression lever is down.. and the engine is reluctant to start unless cylinder 2 compression lever is held back.. Can someone identify the most likely cause? I am looking at 1. Lift pump diaphragm 2. Injector 3. Top end rebuild: head gasket/ lap valves / Clean carbon / leakdown test.. 4. Fuel injection pump gasket if all else fails..? Any other suggestions? Opinions on the cause of this knock?? I also noticed smoke coming out of somewhere on the side of the engine near the throttle.. Here is a link to a google drive folder containing a video of the engine/ knock -> http://https://drive.google.com/drive/folders/1jAjZaD9fh4LBdZU_fkwENjBu5WmLs6wN

[tllong]

Update:

I removed the head and found the cylinder 2 exhaust valve totally caked in carbon and not sealing. The valve was sticking out when closed from all the carbon and I think the clanking sound was the piston making contact with the valve in combination with The cylinder 2 fuel injector being clogged with carbon and barely spraying any fuel.

The lift pump diaphragm was trashed and most likely the cause of the fuel entering the crank case.

I have ordered replacement nozzle assemblies for both injectors and have already cleaned the head and lapped the valves: leak down test shows no leaking.

I am replacing the fuel lift pump, cleaned the mixing elbow, new gaskets on lift pump, head, exhaust, new zinc, checked tolerances (all good).

The cylinder tops both had a lot of carbon caked on, but look okay otherwise.. both cylinders look level and good after a cleaning..

The injection limiter was sort of an after thought to all of these issues... but it is nice to have it in place.. i tested it out before i tore the engine apart and it is effective at limiting the engine, but otherwise seems to not have contributed to the major issues.

[MikeHoncho]

if the valve was hitting the top of the piston there is more work to do than just clean it up.

[Wotname]

Originally Posted by tllong

Update:

I removed the head and found the cylinder 2 exhaust valve totally caked in carbon and not sealing. The valve was sticking out when closed from all the carbon and I think the clanking sound was the piston making contact with the valve in combination with The cylinder 2 fuel injector being clogged with carbon and barely spraying any fuel.

The lift pump diaphragm was trashed and most likely the cause of the fuel entering the crank case.

I have ordered replacement nozzle assemblies for both injectors and have already cleaned the head and lapped the valves: leak down test shows no leaking.

I am replacing the fuel lift pump, cleaned the mixing elbow, new gaskets on lift pump, head, exhaust, new zinc, checked tolerances (all good).

The cylinder tops both had a lot of carbon caked on, but look okay otherwise.. both cylinders look level and good after a cleaning..

The injection limiter was sort of an after thought to all of these issues... but it is nice to have it in place.. i tested it out before i tore the engine apart and it is effective at limiting the engine, but otherwise seems to not have contributed to the major issues.

So far so good, you might have dodged a bullet! Let us know how well it runs once you have it running again.

[Compass790]

Good result!
You got off lightly, carbon buildup is a common problem if they dont spend much time loaded & up to temp. Worse of course on raw water cooled engines.
The injection limiter could contribute to carbon buildup if it was overfuelling all the time. I.E. blowing black smoke.
The exhaust v/v on our engine hits the piston every time we use the decompression lever but it only knocks my hand back as there is no cable & it's been ok for years.

[tllong]

Originally Posted by MikeHoncho

if the valve was hitting the top of the piston there is more work to do than just clean it up.

Thanks for your comment. Can you expand on what ‘more work’ could entail? More information would help myself and readers know what to look for when this issue is encountered. Much appreciated.