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Diesel This is a forum dedicated to diesel engines and their applicable accessories.


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  #11  
Old 05-07-2012
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Re: Runaway Yanmar 2qm15 HELP!

Not too familiar with the Yanmars, but did you have the governor apart? The behaviour sounds like it's simply stuck at 'full throttle' internally regardless of where the 'throttle' is set...
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Re: Runaway Yanmar 2qm15 HELP!

Yeah that's one of the things I want to check when I get out there again. Think I will disconnect the throttle limiter and manipulate the injector pump manually. Thanks
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Re: Runaway Yanmar 2qm15 HELP!

When you honed out the cylinder did you use WD40 or some kind of light lube oil ? if so that will ignight and run until the WD is all burned off.
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Re: Runaway Yanmar 2qm15 HELP!

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Originally Posted by cptjak View Post
When you honed out the cylinder did you use WD40 or some kind of light lube oil ? if so that will ignight and run until the WD is all burned off.
Don't ask me how I know this very Scarry!
Just curious, a light film or puddles on top of the pistons?

Paul T
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Runaway Yanmar 2qm15 HELP!

On older simple engines, Y2qm included, injector pump is calibrated individually by inserting special shim washers. It is crucial to place washers exactly same way, if pump is disassembled.
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Re: Runaway Yanmar 2qm15 HELP!

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Originally Posted by CrazyRu View Post
On older simple engines, Y2qm included, injector pump is calibrated individually by inserting special shim washers. It is crucial to place washers exactly same way, if pump is disassembled.
I think it is the pump/governor assembly. A new or re-built one "out of the box" might work

Paul T
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Re: Runaway Yanmar 2qm15 HELP!

I have no idea if the shims were put back in the same order. If they are off would that cause excessive fuel to the injectors? On the second disassembly there was oily residue on both pistons and the rear #1 compression ring was stuck (these are new rings). The exhaust ports showed heavy carbon build up for having only ran for a few minutes. The new oil was very dark as well and smelled like self lighting charcoal. I freed the ring and when reassembled the second time I cleaned good and lubricated both the cylinder walls and the rings were free moving and well lubricated (and as I mentioned before the cylinders were professionally honed and tolerances were within spec). Kinda wondering if the ring might have stuck again?? I've been racking my brain trying to think of where oil might be entering the intake. If the ring is stuck again what would cause that? Would it be caused from oil entering the intake? Where the heck could the oil be coming from? The valve seals are new too.
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Re: Runaway Yanmar 2qm15 HELP!

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Originally Posted by miamiz View Post
I have no idea if the shims were put back in the same order. If they are off would that cause excessive fuel to the injectors? On the second disassembly there was oily residue on both pistons and the rear #1 compression ring was stuck (these are new rings). The exhaust ports showed heavy carbon build up for having only ran for a few minutes. The new oil was very dark as well and smelled like self lighting charcoal. I freed the ring and when reassembled the second time I cleaned good and lubricated both the cylinder walls and the rings were free moving and well lubricated (and as I mentioned before the cylinders were professionally honed and tolerances were within spec). Kinda wondering if the ring might have stuck again?? I've been racking my brain trying to think of where oil might be entering the intake. If the ring is stuck again what would cause that? Would it be caused from oil entering the intake? Where the heck could the oil be coming from? The valve seals are new too.
"The new oil was very dark as well and smelled like self lighting charcoal"
An indication that raw fuel is getting into the crankcase? You mentioned earlier that it "breathes" 3 or 4 seconds after shut off, in or out? If there is oil in the intake manifold that could be an indication it is being sucked or pushed from the crankcase. Make sure the crankcase breather hose is free.
You might try disconnecting it the next time you start it. How long has it run since your last assembly. If not long, that is a lot of fuel going into the crankcase. An oil analysis would show how much, if any. I think there are two possible problems, oil getting into the cylinder or the injector pump. I would suspect the pump first. If a ring or rings were stuck it might be hard to start.
A compression test would probably show that. Proper oil level?

Paul T
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Re: Runaway Yanmar 2qm15 HELP!

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Originally Posted by dabnis View Post
"The new oil was very dark as well and smelled like self lighting charcoal"
An indication that raw fuel is getting into the crankcase? You mentioned earlier that it "breathes" 3 or 4 seconds after shut off, in or out? If there is oil in the intake manifold that could be an indication it is being sucked or pushed from the crankcase. Make sure the crankcase breather hose is free.
You might try disconnecting it the next time you start it. How long has it run since your last assembly. If not long, that is a lot of fuel going into the crankcase. An oil analysis would show how much, if any. I think there are two possible problems, oil getting into the cylinder or the injector pump. I would suspect the pump first. If a ring or rings were stuck it might be hard to start.
A compression test would probably show that. Proper oil level?

Paul T
Been thinking about this a little more. First off, my diesel "hands on" experience has been with VW turbo and non turbo engines and a 3-71 Detroit two stroke diesel, aka "screaming Jimmy", in a commercial salmon troller. On the VW engines I replaced timing belts, changed injectors, glow plugs and set the injector timing with special tools and dial indicator gage, that is about it.

So, back to the drawing board:

1. The engine ran OK until you took it apart
2. From shop manual diagrams the injector pump/governor/ fuel distribution systems have lots of small parts, scary to even think about taking one apart
3. A number of possible problems already mentioned

Suggestion;

1. Take the engine, less transmission, to a qualified shop
2. Explain everything that has taken place
3. Have them analyze it, compression test, oil analysis,inspect timing, dis-assemble and re-assemble if necessary
4. Have them do a "bench test run" while you watch
5. Re install and then go sailing

Paul T
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Re: Runaway Yanmar 2qm15 HELP!

Thanks Paul for your help. The 2QM15 is a pretty simple engine..no glow plugs or turbos or anything. Just fuel, air and combustion (which makes this that more frustrating!). I did take the injector pump and have it rebuilt. Also I did do a garage analysis of the oil. Poured it into a glass jar and let it sit for a few days. There was no visible separation but there was muddy (cabon I assume) at the bottom when I dumped it out. Checking the crank case ventilation hose & housing is on my list of things to check. I'll try running disconnected. Just bought an oil pressure gauge so I'll get some reading on that too. Will also make some temporary injector shims to see if adding additional space will have any impact. I will also pull the head and drop the intake valves to see if I can see any oil residue. Theoretically, it should be dry right? Also ordered a new head gasket. The thought of pulling the engine the third time makes me want to learn to actually "sail" my boat! LOL
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