yanmar 2gm20

[John Howitt]

My engine starts and runs beautifully.
I run it against the dock in gear.
It will run for about an hour, and then the RPM's start to drop.
after that it will not run below 1000 RPM.
It always restarts and runs great, but it will not idle.
I have adjusted the idle speed to about 850-875.
Last year it got the tank drained, and new fuel with stabilizer, a new racor filter, new fuel lines and a new fuel pump.
It has been sugested that it could be the governor.
I have absolutely no idea how to test, it adjust it, or replace it.
Has anyone had a similar experience?

 

[kloudie1]

I am not a diesel expert, but it doesn’t sound like a governor problem. The problem sounds more like something that is happening as temperature increases.. If the engine is not overheating as verified by temperature measurements, ya may have valves that are in need of adjustment.. Pull the valve cover and check that the valve clearance “lash” is correct. Have the high pressure fuel lines been bled and the low pressure lines tightened and checked for leaks? A very small air leak on the suction side of the lift pump that opened at higher temperatures in the engine box could do that.. Also, make sure that you have plenty oil pressure when hot.. again, check with a gauge against the Yanmar specs.. not likely, and only proceed there if fuel system and valves don’t fix the problem ..Good luck, John.

 

[John Howitt]

Thanks for the advice about the valves. They have not been serviced in the four yrs that I have owned the boat.
Oil pressure and engine temperature are both good. .The enginge reaches temp and continues to run well for a period of time and then starts to act up.
It does not start as soon as it gets warm.
There are no fuel leaks, and I'm not sure about where to look for an air leak.
One fellow that I met, with the same boat has an electric fuel pump as well as the one on the engine,mine does not, but it was never a problem before, so I don't want to try a bandade solution.

 

[Bill Roosa]

Starved for air?

Check your air cleaner. What you describe is not your valves. Those either work right or don't They don't change dramatically upon reaching operating temp and would not effect the idle.
Assuming that you do not have a fuel problem due to the fact that it re-starts. Probably would not do that if there was air in the system and you say there is not a fuel leak and the filters are new.
It sounds like the engine is being starved for air. Two things can cause that, an air cleaner plugging the intake somehow or the exhaust elbo being plugged.

Is there any smoke from the exhaust when the RPMs drop? What color?

 

[Steve Dion]

I suggest that you get an owners manual for the 2GM. They have advice on things to check and how to repair them.

There is a good chance that a Yanmar mechanic can spend a couple of hours with you (about $100/hr) and help you diagnose your issues.

 

[John Howitt]

The mixing elbow was changed two yrs ago, and the exhaust smoke is what I would consider normal in colour.
I brought the air filter home and cleaned it out with solvent and I ran it without the filter,it makes no difference.
The mechanic is the person who sugested that it may be the governor.
I have to wait another week before he can come look at it.
I just thought that I would see if anyone else has had a similar experience and could offer some advice.

 

[Don12364]

Something to Check

I had a 2QM15 years ago which developed a similar problem.
In their original design Yanmar returned the spill fuel from the injectors back to the top of the engine fuel filter. All was well until the injectors got a little worn and began passing tiny bubbles of combustion gas into this spill stream.
Eventually there was sufficient build up of gas to create a partial air lock and starve the engine of fuel.
It is easy to check. Just look to see if there is a fuel pipe which joins the injectors together and then goes directly to the filter.

When I told them about it, Yanmar's cure was to free issue a modified banjo coupling for the filter with an extra leg to take this spill fuel (and bubbles) back to the top of the tank.
See if you have this pipe too.

You may have neither and the spill line taken back to the tank directly which is better and simpler.

 

[Mike Holibar]

I had similar symptoms recently, Inspected filter and found bug. Replaced filter (primary) treated with Fuelset and problem fixed. Might be worth inspecting your filter just to eliminate that possibility.

best regards,

 

[kloudie1]

Quick note, Bill.. Because steel expands about 10% more than cast iron when heated, valve clearances can close up when the engine comes to uniform temperature.. since the cast iron block is somewhat cooled and the pushrods see a higher temperature, the differential expansion is greater.. so if a valve is set much too tight, it may begin to not seat as the temperature increases, resulting poor running and eventually burned valve seats. It depends on the individual engine design, but most water cooled, cast iron block engines with steel pushrods close clearances slightly as they ‘heat soak”.. Part b of thought on this one is that as the valve seat and valve wears, the clearance can, in some engines, decrease. So with a slowly decreasing clearance over time, a valve if not reset may get to a place where it goes to 0 lash at higher temperature.. and may not seat

 

[Paul S]

you are getting fuel, so it is not that. Could be injectors. You can pop them off and have them rebuilt or exchange them.

what fuel filters do you have. you should have a 30 micron primary and a 10 secondary. anything smaller it will plug.

I would strongly recommend taking a diesel class at Mack Boring or other local classes. It is worth its weight in gold

If you have good fuel, clean filters, it should run.

Did, whoever winterized the motor, tape up the air filter intake or otherwise plug it? Wouldn't be the first time this happened.

How is the fuel tank vent? If it is plugged, it will create a vacuum and cause poor running.

I am not a mechanic but sounds like fuel of some sort, either not vented tank, plugged or incorrect (too fine) fuel filter..the mechanical fuel pump will have issues overcoming a bad/clogged/incorrect filter and a vacuum on the fuel tank ...doubt it is the injectors, but it is about the time to service them proactively anyway..easy enough to do yourself.

blow through the tank vent to ensure it is clear befor doing anything.

Paul

 

[Capn Pete]

If you need a 2GM20 owners' manual and don't feel like springing for a print copy, here's the Yanmar site you can download it from:

http://www.yanmarmarine.com/theme/y...iles/Operation manuals/GM-OP Manual-Multi.pdf

Pete
s/v EmmieLou (O-322)
Little Silver, NJ

 

[John Howitt]

Thanks for all the ideas. I will check the tank vent today, and I think that for the few dollars that it costs, I will change the filters again.
On the bright side, it is all clean and waxed, loaded, and ready to go.

 

[Ray Bowles]

John, Adjusting the valves is something that needs to be done and is a easy job. With a manual almost anyone with some mechanical ability can do this. If it is something you might not feel good about doing the first time then anyone that has ever adjusted valves on a foreign car could do it for you. On the Yanmar engines I am familar with they do not use bucket shims or caps and therfore do not require any gear other than basic tools and a valve cover gasket. I don't think this is the problem.
I think that "Donalex" could be right on with his answer and I would check this first.
You can eliminate the vent question by removing the fuel filling cap for the test.
Filters should not effect the engine after running unless they have a "jelly like material" that builds up over running time but there would be a residue that falls off into the bottom of the filter when flow stops.
Look ar "Donalex" first.
Good luck, Ray

 

[John Howitt]

I finally got the mechanic down to the boat this morning.
After running it for awhile, he said that it runs too well to be a fuel or filter problem, and that there is no way that there is air getting into the system.
He said, it is definetly a problem with the governor. He recommended an injector pump lubricant. $20 for 1.92 liters, enough to treat 3000 liters of fuel. ( hope it has a long shelf life.)
He said that the low sulpher deisel fuel acts almost like a solvent, causing problems with valves and pumps.
Now all I have to do is run it, working the trottle up and down, and hopefully it will cure the problem after awhile.
I've got my fingers crossed.
I'm really hoping to avoid a $700 repair bill, plus labour and the new 12% HST ( H ated S crew Tax) that our beloved liberal government implimented July 1

 

[Cayennita]

While at it, check your exhaust hose. They tend to get soft and collapse as the engine exhaust gets hotter, creating a restriction and dropping RPM's.

 

[Paul S]

got to love the mechanic-in-a-bottle solutions. Hope it works!

 

[kloudie1]

John, the other one that I haven't seen discussed is a plugging screen in the fuel tank pickup tube. Had this happen on a delivery form Pensacolla one night.. pertty much the same symptoms .. We'd blow the tube out and it would run another hour, almost exactly, the same for 4-5 repetitions .. then we sailed.. and blew it out to get into the harbor.. At home, we pulled the tube out of the tank and removed the little screen at the tip .. never had a problem since. The Racor will catch the stuff that used to plug the screen. There have been discussions of this problem on this forum..
Take the screen off anyway .. good luck .. Oh yeah.. it would restart if we let it sit for a couple of hours without blowing it out too.

 

[John Howitt]

The problem seems to be almost cured. There was definately an improvement with the addition of the lubricant to the fuel.
I had the boat idling, and the rpm's were starting to drop, we used the little plunger on top of the racor to increase the pressure, it helped a little bit, so I put an electric pump in line just after the filter, and changed the filters just because (they both looked like new.)
Of course the bleeder screw on the secondary filter decided to pick this time to strip the threads. I went to WM and picked up a larger diameter bolt and a new nylon washer. Drilling and tapping a new hole was a bit of a challenge in the confined space, but the job went well enough (refur to Ross's post about repairs).
Fortunately I only live 11 minutes from the boat.
Only one trip home for more tools.
The boat never had the second fuel pump before, I can't figure out why it needs it now , but as long as it works I'll get over it.
It did make bleeding the system so much nicer.
So far so good. touching wood.
Thanks for your suggestions they were much appreciated