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Discussion Starter · #1 ·
A few month back bringing Kare Knot down the intercoastal a slow oil leak caused my oil level to run low. Since it was coming from the back of the engine I decided to pull the engine and change all the seals and gaskets. I boomed the diesel into my tender and lugged it tom my garage. In the process of cleaning I broke a ring and decided to change the rings. Ordered one of those $15 dollar honing tools and commenced to destroy the inside of my cylinder walls (don't try to do this yourself!) Thinking that I had done a good enough job I reinstalled the engine (not fun!). Any way after a few days of trying to get the fuel lines to bleed the 2 banger came to life. Like 3500 rpm of life!!! Anyway if you've never had this happen it will scare the crap outta you! Finally covered the intake and the engine reluctantly sputtered to a stop. Decided to drink a beer and give it a once over. Nerves calmed I tried again with the same results. My first intuition was it was the injector pump which I took apart as part of rebuild (allso not a good idea!). So took it to an injection specailist and forked over $200 for my precision tuned pump. Installed the pump and holy crap it ran away again. Now my worst fear set in... my crappy honing job! I winched out the engine again and brought it for a professional honing. The checked the wall diameter, ring gaps mating surfaces and put a nice cross-hatch on the walls. Meanwhile smeone stole my $2000 dingy and engine! Anyway winched the motor in for the second time. Checked ever detail while reassembling. Started her up and it fricken ran away again. I'm out of ideas... Pulled the injectors and will have them tested this week. If this doesn't fix it I'm all out of ideas. Anyone with any other ideas I sure would appreciate it! Here's a list of what I chaged so far:

New rings
Front & rear main bearings
Rod bearings
Front & rear seals
Injector mating seals
New head gasket (well all new gaskets)
Replaced the soft fuel lines.
Rebuilt injector pump
2 quarts of oil
Valve stem seats

Professionally rehoned and certified valve steams, seat ok, ring gap and mating warp ok

Now just some notes, blowing blue smoke. Disconnected fuel supply and the engine stopped. The spring between the injector pump and the throttel inhibitor seems looser that it should. Moving the throttle while running does not impact speed.

Any ideas would be greatly appreciated!!!!!!!!!! :confused:

Thanks EZ
 

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Discussion Starter · #4 ·
Thanks for your replies. First the throttle cable is not connected at this time but I've turned it while the engine is running and it will rev faster but not slower (strange). I have had the breather cover completely off while the engine was running an it made the engine run faster because I could no longer control the air supply by way of the air intake. Not sure what you are talking about when you say lift pump diaphram? The oil pump on the 2qm is external on the flywheel side and driven by the cam shaft. Yes the engine ran very well before.
 

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Thanks for your replies. First the throttle cable is not connected at this time but I've turned it while the engine is running and it will rev faster but not slower (strange). I have had the breather cover completely off while the engine was running an it made the engine run faster because I could no longer control the air supply by way of the air intake. Not sure what you are talking about when you say lift pump diaphram? The oil pump on the 2qm is external on the flywheel side and driven by the cam shaft. Yes the engine ran very well before.
Not sure what kind of lift pump you have. Some older ones had a diaphram activated by a lobe on the cam. A torn diaphram might leak fuel into the crankcase diluting the engine oil, "over filling" the crankcase, but that is probably a stretch? You said you took the injector (high pressure) pump apart
which could be risky business. As the engine ran fine before you took the pump apart I would think the pump is your prime suspect as the injectors are pretty stable, "going bad" very gradually, if at all. Perhaps if you go to a well respected shop and bought a re-built pump, giving your old one as a "core", might do the trick?

Paul T
 

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I think the OP said in his original rundown that the runaway problem came up after replacing engine gaskets, honing, and rings, but before he messed with the high pressure pump. He opened that up while trying to fix the runaway.
 

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Discussion Starter · #7 ·
Thanks Paul. Just got back from the injector shop. Had my injectors flow tested and they are fine. The injector pump was professionally rebuilt also. The lift pump on the 2QM is external. Now that kinda points me to two possible culpits... Either there is blow by on the pistons or something assembled wrong on the throttle internal linkage. Like I said the spring that goes from the throttle inhitor to the injector pump arm seems looser than is should. Thought I remember it being pretty tight to get off... God I miss my memory!
 

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Thanks Paul. Just got back from the injector shop. Had my injectors flow tested and they are fine. The injector pump was professionally rebuilt also. The lift pump on the 2QM is external. Now that kinda points me to two possible culpits... Either there is blow by on the pistons or something assembled wrong on the throttle internal linkage. Like I said the spring that goes from the throttle inhitor to the injector pump arm seems looser than is should. Thought I remember it being pretty tight to get off... God I miss my memory!
Maybe the spring was stretched when removing it? I still suspect something wrong with the pump?

Arf, " My first intuition was it was the injector pump which I took apart as part of rebuild (allso not a good idea!). " Not sure when exactely he did the pump? If there was that much blow by it might be hard to start?

Paul T
 

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Discussion Starter · #9 ·
After thinking, the injector pump is external but has a lifter arm into the crank case and actuated by the cam. However, having just rebuilt the engine and new oil, I don't think that on first start there would be dilution yet... The runaway was immediate. Good point on hard starting - in this case it starts easy which points us away from low compression. Could it be that the rings need time to seat? If I control the throttle by partially blocking the air intake and let it run for a while would that damage anything....would they eventually seat? there seems to be allot of vacume in the head (that may be normal) but after I shutoff the engine it takes a heavy 3-4 second breath thru the intake. But I thought if something were creating too much vacume that it could suck oil up or the reverse if there was too much crank case pressure...
 

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After thinking, the injector pump is external but has a lifter arm into the crank case and actuated by the cam. However, having just rebuilt the engine and new oil, I don't think that on first start there would be dilution yet... The runaway was immediate. Good point on hard starting - in this case it starts easy which points us away from low compression. Could it be that the rings need time to seat? If I control the throttle by partially blocking the air intake and let it run for a while would that damage anything....would they eventually seat? there seems to be allot of vacume in the head (that may be normal) but after I shutoff the engine it takes a heavy 3-4 second breath thru the intake. But I thought if something were creating too much vacume that it could suck oil up or the reverse if there was too much crank case pressure...
Maybe when re-assembling the engine you reversed the manifold gasket or a flange somewhere and the engine is pulling air from within the crankcase bringing oil with it? The 3 to 4 second "breath" would indicate excessive pressure or vacuum in the crankcase. If it is breathing in the vacuum may be pulling oil along with the air. If breathing out oil may be being pushed up the breather tube into the intake manifold. If the inside of the manifold has a lot of oil in it that may be the cause. However, the fact that you can stop the engine with a rag in the intake may dispell that theory? A rebuilt pump out of the box would be an easy try.

Paul T
 

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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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Discussion Starter · #12 ·
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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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!
 

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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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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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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 :D

Paul T
 

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Discussion Starter · #17 ·
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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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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"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:D

Paul T
 

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Discussion Starter · #20 ·
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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