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Old 22-09-2013, 07:04   #16
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Re: Yanmar 1GM10 loses power, please help

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New fuel, new fuel tank, new filters. Fuel is as good as it will get. Maybe there is some pump / injector treatment I can run through it? How do I go about adjusting the governor?

Thanks

Then I think you have to have air getting into your fuel line someplace.
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Old 22-09-2013, 07:06   #17
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Re: Yanmar 1GM10 loses power, please help

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Then I think you have to have air getting into your fuel line someplace.

PS I think the fact that it tends to happen when you throttle back is a clue. When you're running higher rpms the flow of the fuel may be enough to keep air from getting in via a tiny leak, but when you slow the engine down, the fuel slows down and air pressure can push its way in.
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Old 22-09-2013, 15:18   #18
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Re: Yanmar 1GM10 loses power, please help

I don't think there's a leak in the line between the tank and past the first filter because I put 20 PSI pressure in the line and it held for 10 minutes. The only place that air could be getting in is the bleed screws but I tighten those down pretty tight without stripping them.
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Old 22-09-2013, 16:25   #19
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Re: Yanmar 1GM10 loses power, please help

Did you replace the copper washers on the banjo bolts? They work-harden and can cause tiny leaks. I see you pressure-tested which probably rules them out, but it's a thought.......

Sounds like a real bugger - good luck with it!

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Old 22-09-2013, 16:53   #20
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Re: Yanmar 1GM10 loses power, please help

Hum. Can't remember if you checked the discharge elbow for carbon buildup or not. The high RPM sputtering sounds like excessive back pressure which could be a partly blocked discharge elbow. Runs ok at 2000-2500 but fluctuates higher, could be discharge elbow

Have you checked your valve lash lately?
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Old 22-09-2013, 23:21   #21
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Re: Yanmar 1GM10 loses power, please help

I will check the discharge elbow tomorrow. What is a valve lash? Thanks
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Old 23-09-2013, 01:32   #22
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Re: Yanmar 1GM10 loses power, please help

A quick search on Google suggested it could be:-
* "O" rings and/or copper washers at the fuel filters.
* A partially blocked exhaust elbow.
* Faulty lift pump.
* Faulty injector.

Use of an infra red thermometer may be instructive.
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Old 23-09-2013, 09:38   #23
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Re: Yanmar 1GM10 loses power, please help

Valve lash, is valve clearance. I could see where a exhaust valve if it was very loose could cause some issues. Set to .008" when engine cold and piston at tdc on compression stroke
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Old 23-09-2013, 09:45   #24
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Re: Yanmar 1GM10 loses power, please help

I agree with sailorchick, check the exhaust elbow for blockage. It is a common problem with this engine and it is an easy thing to rule out before you get in too deep. The next thing I would check is the governor and then have the injector pop tested.
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Old 25-09-2013, 07:30   #25
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Re: Yanmar 1GM10 loses power, please help

There was some blockage in the exhaust elbow but it didn't seem too bad. I cleaned it out and afterwards the engine seems to run a bit better at the top end. It will make 3000 RPMs without falling back to 2500-2700 so it must have helped. Although its not running like a top, it seems to be improving little by little. I will put some fresh oil in this weekend and tighten everything up, replace the copper washers under the bleed screws and some general TLC. Thanks all for your help.
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Old 25-09-2013, 07:38   #26
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Re: Yanmar 1GM10 loses power, please help

Having a blocked exhaust elbow will result in carbon build up in the cylinders. You may want to run her at 3,000 rpm for a good long time (at least 30 minutes) to burn the carbon out.

I forget, did you adjust the valves? That would be my next step, mostly because that's all I know how to do.
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Old 25-09-2013, 08:08   #27
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Re: Yanmar 1GM10 loses power, please help

We ran it for about an hour last night and the performance steadily got better, starting at 2700-2800 and increasing - by the time I put it away it was steady 3000+ and bursting up to 3300 rpms. That must have been the carbon burning out. It had probably been run 4 hrs with the 2000 max problem condition so probably plenty carbon built up. I don't know how to adjust the valves - need to learn that.
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Old 25-09-2013, 08:55   #28
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Re: Yanmar 1GM10 loses power, please help

Adjusting the valves is relatively easy and should be done annually.

The valve cover gasket is rubber, so need to buy a new one unless you already have leaking there. It only requires a screw driver, a wrench and a feeler guage, I think 0.2mm. It does require two people, one to view the fly wheel while the other turns the crank shaft.

And make sure piston is on the compression stroke TDC, with both valves closed, when you make the adjustment.
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Old 25-09-2013, 09:19   #29
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Re: Yanmar 1GM10 loses power, please help

Ok, thanks for the instruction. I have the manual so I can fill any details with that.
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Old 25-09-2013, 15:39   #30
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Re: Yanmar 1GM10 loses power, please help

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......, replace the copper washers under the bleed screws and some general TLC. Thanks all for your help.
A quick aside:
If for some reason you are someplace where you can't replace the copper washers, the old ones can be "re-conditioned" by heating them up to dull red and cooling slowly. This anneals them (makes them soft again).

New is better as you get the original thickness but annealing the old ones can get you out of a pickle in remote location.
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