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Old 19-04-2013, 13:24   #1
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Yanmar YSM8 Will Not Start.

I need some help. The 35 year old Yanmar YSM8 in my Pacific Seacraft 25 (s/v Serenity) will not start. The engine last run about 5 years ago. It cranks over well. I have tried the following:

1. New fuel lines where needed and filters. They were a mess from tank to engine.
2. Cleaned out the exhaust mixing elbow. A filthy, rusty, carbon, cruddy mess.
3. Removed the valve cover (I read it somewhere but don't know why. Had to try).
4. Used WD-40 as starting fluid. Nothing.
5. I tried to remove the injector body but it is really stuck in there.
6. High-pressure fuel pump emits very small amounts of fuel intermittently, but seems high pressure. I don't have a gauge.

There seems to be decent compression when I try hand cranking, kinda like a lawnmower resistance, but a lot heavier flywheel. The compression release seems operable and not engaged. The shut off cable is not engaged (maybe stuck inside?). My next suspect is compression.
There is also decent suction at the intake, but not enough to cause a hickey on my forearm or anything. She definitely breaths. I don't see a glow plug or anything electrical, but there might be an electrical cause?

I honestly do not know what to try next. Is there a way to use another starting fluid or light it off somehow? Good fuel lines bleeding method? If anyone has any ideas, I would love to hear them.

Thanks, Jerry
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Old 19-04-2013, 13:31   #2
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Re: Yanmar YSM8 will not start.

I have has good success spraying some silicon spray lubricant in the intake. Less volatile than starter fluid and will not cause compression lock...it works well for me it's an farmers trick.. we know diesels..
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Old 19-04-2013, 14:21   #3
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Re: Yanmar YSM8 will not start.

Thanks, I'll see if there is a can of silicone around here. There used to be. I was thinking of kicking the engine since I tried everything else, but she is starting to grow on me despite her disobedience and defiance.
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Old 19-04-2013, 16:13   #4
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Re: Yanmar YSM8 will not start.

when you crack the fuel pipe loose at the injector pump. You should have fuel jump out 2" or so. If it's less the IP may need to be refreshed.
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Old 19-04-2013, 17:51   #5
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Re: Yanmar YSM8 will not start.

Im not quite clear on the injector pump line. Are you saying crack loose the line from injector pump to injector, at the injector pump after cranking it over? And when I loosen the banjo bolt fuel should spurt out due to pressure built up? I'll check it out. I am getting anxious over this. The idea of rebuilding the injector pump is not so bad. Im going to try getting diesel fuel into a spray bottle and try that. the silicone seemed to give me a couple pops, but not certain.
Jerry
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Old 19-04-2013, 19:10   #6
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Re: Yanmar YSM8 will not start.

I think the problem might be bleeding all the air out of your fuel system. I don't know how Yanmars are but if there is a nut where the fuel line from the injector pump meets the injector then that is the one to open after you've bled the system to the fuel injector pump to clear all the bubbles out of the line. While it is open, crank the engine and see if you can get a clear intermittent stream (no bubbles). If it is clear then crank the engine while tightening the nut. Once the nut is tight then close the compression release while cranking.
Don't crank the engine with an electric starter too much. Give it a little break from time to time to let it cool down. Also, if it is an electric starter keep the compression released until you have cleared all the bubbles out of the line before closing compression. Too, if your battery is low and doesn't spin the engine fast enough it won't start very well.
Good luck and let us know how it all works.
kind regards,
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Old 20-04-2013, 22:09   #7
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Re: Yanmar YSM8 will not start.

I think I need to pull or remove my injector and clean it up. I removed the hold down flange and tried to wiggle it out with an 18" channel lock and was unsuccessful. How do I remove the injector housing/body?
Putting diesel fuel in the intake got some chug-chugs out of her, but she is starving for fuel.
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Old 23-04-2013, 23:10   #8
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Re: Yanmar YSM8 will not start.

The injector needle was corroded at the very tip and seized in the body. It took a pry bar and a lot of tap-tap-tapping on the injector body to free it. I removed the needle by using a flat washer and hammer to push needle flush with body. Then I used a small center punch to tap needle into body a couple mm. Using an X-acto needle I was able to push it out far enough to pull with a pliers. Pain in the ass. I cleaned and inspected everything, and except for the needle tip, everything is in good shape. I installed it just before dark and was unable to get her started. I suspect air in the system or injector pump. with needle seat in order I should have a running engine, but the rough tip will likely cause lower performance.
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Old 23-04-2013, 23:46   #9
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Re: Yanmar YSM8 will not start.

It's possible for a mechanic to clean injectors but in my experience and from what you describe I would do the following. Remove the injectors(make sure the little copper washers comes out too) mark the injector pump and take it all to a repair specialist to be cleaned and pressures reset to factory standards. Disconnect the starter battery so no one can turn the engine over. Now clean the fuel tank thoroughly before reassembly of all the components. When tightening nuts, banjo unions etc don't over tighten as it will stretch the threads and cause air ingestion. Bleed the system and fire the engine. The reason for all this is that the previous owner never cleaned the tanks and over the years has acumulated fine sediment/acidic fuel residues/water particles in the fuel tank which have entered the fuel system and lain dormant at the pump and injectors causing internal corrosion. It's one of the most common fuel problems on boats.
Do it once, Do it right.
I hope this helps.
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Old 24-04-2013, 00:45   #10
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Re: Yanmar YSM8 will not start.

Theres an old trick my daddy tought me, remove the injectors and put about an oz of automatic transmission fuild in each cylinder! let it sit overnight, replace the injectors (properly bled of course) and start her up ! sometimes when a diesel sits for a long time they lose the total compression they should have ! and the tranny fluid seems to cure this problem! she will smoke like hell for the first 10 minutes or so, but will clean up and run much better ! just a old trick , it might work for ya !!
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