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Plugged crankcase breather? excessive blow-by? Lift pump diaphram, it it has one, torn, allowing fuel to mix with crankcase oil? Excessive injector pump pressure? "weak" injector
springs? Injector pump not really fixed? Did it run Ok before you worked on it?

Paul T
 

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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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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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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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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.
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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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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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
Depending on the condition of the engine some blow-by vapors may condense
and be visible in the intake manifold but I wouldn't think there should be puddles of oil anywhere. Intake valves should be fairly clean. If the pump/ governor assembly is all in one housing I guess you can assume it was properly re-built?? If you took out the cam maybe it wasn't re-installed in the right position although some cam drives I have seen are off center so you can only install them in the correct position but the cam marks and crank marks need to be aligned. I think that if the timing was very far off it wouldn't run
at all. The 3 to 4 second "breathing" thing has me puzzled? So far all I can think of is:

1. Bad pump/governor
2. Timing way off
3. Lube oil getting into the intake tract, if that is happening I think the engine would go beyond 3,500 RPM and eventually scatter. If it stops at 3,500 I would suspect the governor/"throttle" linkage or assembly is stuck on "full open"

If you don't have a really good detailed shop manual you should get one, well worth the cost. Let us know what you find. You may have too much faith that the pump was properly re-built? Just a thought?

Paul T
 

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You guys are great troubleshooters! However a truly seasoned mechanic would ask the the most relevant questions first. Which should be..........wait for it........ "are you Polish by chance?" which I would respond "why yes I am! How did you know?" Because you have a 2 cylinder engine and you have a 50/50 chance of getting TDC right. Which would be the flywheel side and not the front you idiot!

Yeh I haven't verified it yet but I aligned timing marks on the crank gear with the cam gear based on forward cylinder being #1. It's the rear (flywheel cylinder)! Feeling really stupid at this point but to my defense the Yanmar manual only mentions the TDC orientation once in the entire manual and it's buried inside a paragraph in the middle of the book! I have to say that I have a new new found respect for Yanmar's if they would even start in this scenario! Let you know how it turns out this weekend. Thank god Paul is in California he can't come down to Miami to kick my Ars for waisting 2 two hours of his life!!!
Miamiz & Faster, thanks. I hope that is the problem, easy to fix. It is amazing to me that it would even run that way, let alone run up to 3,500 RPM. Not a waste of time at all, one can always learn from other's experiences. Let us know how it works out.

Paul T
 

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OK, I think I have got it? If you used #2 piston for TDC the timing is 180degrees retarted. Every engine, gas or diesel, that I have worked on uses Piston #1 for TDC settings. Which means:

1. The real intake stroke becomes the power stroke
2. The real compression stroke becomes the exhaust stroke
3. The real power stroke becomes the intake stroke
4. The real exhaust stroke becomes the compression stroke

So what, you ask? The fuel is being squirted in on the intake stroke and eventually accumulates to the point of being enough to ignite on the compression stroke. As the fuel is not all being burned because of the mixed up strokes more accumulates and the engine starts to run away.

I think

Anyway the timing thing is easy to fix, let us know.

Paul T
 

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OK, I think I have got it? If you used #2 piston for TDC the timing is 180degrees retarted. Every engine, gas or diesel, that I have worked on uses Piston #1 for TDC settings. Which means:

1. The real intake stroke becomes the power stroke
2. The real compression stroke becomes the exhaust stroke
3. The real power stroke becomes the intake stroke
4. The real exhaust stroke becomes the compression stroke

So what, you ask? The fuel is being squirted in on the intake stroke and eventually accumulates to the point of being enough to ignite on the compression stroke. As the fuel is not all being burned because of the mixed up strokes more accumulates and the engine starts to run away.

I think

Anyway the timing thing is easy to fix, let us know.

Paul T
Forgot the 3 to 4 second "breathing" thing. Could be that with the valve timing being so far off that on either the intake or compression strokes a valve is partially opening or closing allowing the intake or compression gases to escape very slowly, I think?

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Hey Paul. I keep my boat on a city moring. Went out there on Saturday but they shut down the shuttle boat that takes residents to their boat. 15MPH winds and 1 foot swells and the guy has the nads to call himself a captian! Yeh I chomping at the bit to get out there. Promise to post a followup. EZ
He is probably afraid of being sued if someone got some spray on them:D
Hope it is the timing thing, easy to fix.

Paul T
 

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Will, Thanks for the tip. Yes I removed everything from the engine during the rebuild. When I inserted the pump I did make sure the rack ball was inserted in the throttle control assembly. It's hard to say at this point if there are any idle issues or not because I haven't been able to get out there to readjust the timing. However, I lost the position on the stop cable and I'm not sure how to get that in the right position to stop the engine. Also the throttle assembly (spring) seems looser than when I took it off. Not sure if something is screwed up there... Once I get the to the boat I'll have a better idea if I am going to need further help getting the throttle assembly and stop cable adjusted correctly. So I have two shims and will torque to spec but how would I know if the fuel delivery is correct? Thanks for your advice.
Sounds like the re-assembly of the pump/governor assembly is tricky business. Suggest one thing at a time:

1. Re-set timing, if it is off as you suspected. If it still runs away:

2. Take pump assembly to a good shop and have them re-calibrate it

Let us know how it works out.

Paul T
 

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The timing marks appear to be right? Not sure about your description of the "pump". Lift pump or injector pump? Can't figure out what loosening it would do. Is the oil level correct? Is it contaminated with fuel? If the blowby is excessive it may be "feeding" the engine extra fuel. Before pulling the pistons I suggest you do a compression test.
Will it idle down and continue to run? Does the injector pump move to effect fine timing settings? If so, it may be off. If the lift pump is suspect you might try a gravity feed fuel source like an outboard gas can.

Paul T
 

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Well, at least you got it running without scattering it. Sounds like there may be a big air leak or it is starving for fuel. Not familiar with the Yanmar injection pump. IIRC, Bosch pumps could move, similar to distributors on gas engines a long time ago. to set the final precise timing. Looks like all those little arm thingies may not be moving properly? Maybe time to take it to a shop for calibration. Maybe it is out of time somewhat?

Paul T
 
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