Mep 831a black smoke won't rev up and shooting flames out the exhaust

[Captainscall]

Be sure the copper washer isn't just stuck in there. If it is, just use a pick to get it out. If the injector wasn't over tightened, it shouldn't fight to much.

I did feel around with a pick. Nothing moved. I felt what I think is a small depression where the washer fits in? Nothing down there was copper colored. It was all a grey metal.

I will be ecstatic if this turns out to be the problem. I will also feel like a moron if this is what I missed the whole time. It is kind of scary that the washer was missing the whole time because it means someone was in there messing with the machine before I got it. Hopefully they did not mess with anything else before I got it. Luckily in the short times I have ran it everything else appears to work. I was able to test most everything and everything appears to operate correctly.


Thanks!!


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[WWRD99]

Just out of curiosity how full is the engine oil? I got a 531 that I put to much in and it smoked and ran like heck.

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[Captainscall]

The oil is slightly below the threads where you check the oil. I would say about half an inch down the top of the threads.


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[WWRD99]

The oil is slightly below the threads where you check the oil. I would say about half an inch down the top of the threads.


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There's no stick in the 831 like the 531 then. Ugh. Mine I can't see much from the filler but I don't know if it's the same on the 831 but the 531 takes under a quart. I didn't have a way to measure the oil going in and guessed wrong big time. On a side note there wasn't a live bug within 50 yards of it and the car muffler I welded to the exhaust was beet red lol...531s are very loud.

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[Guyfang]

On the Yanmar engine, its VERY important that you read in the TM how to measure the oil. I believe there is a passage that tells you how to do it right. I just remembered this little Jem. The first time I did it wrong. And yes, it was a disaster.

 

[2Pbfeet]

I think I might have overlooked something. Would a missing copper injector washer cause it to run the way it is??


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Oh, yes.

Low compression would result in a less than ideal combustion, and therefore further over fueling as the governor advances the fuel lever at the high pressure pump.

However, and it is a big however, those washers are notoriously difficult to see at the bottom of the injector tunnel, especially if they have been gunked up with carbon and poorly combusted diesel. I have pulled apart units that had two washers down there. While not having a washer is bad, having several is also bad due to reduced compression and sealing.

I'm sorry, and I only have vague recollection of this, but I seem to recall flailing around at one point trying to get replacement washers because the Yanmars use copper washers that come in slightly different thickness for different variations on the engine. I do not know what the correct thickness is for your particular engine.

All the best,

2Pbfeet

P.S. I would not go poking around there with a pick as the metal of the head is quite soft. A short of compressed air (carefully! Washers have been known to fly out at speed.), some carb cleaner, and a borescope are your best friends if you have any doubts about the washer being present.

 

[CallMeColt]

I did feel around with a pick. Nothing moved. I felt what I think is a small depression where the washer fits in? Nothing down there was copper colored. It was all a grey metal.

I will be ecstatic if this turns out to be the problem. I will also feel like a moron if this is what I missed the whole time. It is kind of scary that the washer was missing the whole time because it means someone was in there messing with the machine before I got it. Hopefully they did not mess with anything else before I got it. Luckily in the short times I have ran it everything else appears to work. I was able to test most everything and everything appears to operate correctly.


Thanks!!


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It could be it, but you never know. The missing washer would delay timing & cause it to inject fuel late, making combution late & half-assed while the valve is opening. These engines are very robust and will try to run in the most adverse conditions. I have seen them run backwards, pulling air in the muffler and smoke coming from the air filter. Mind you, this is terrible as the oil pump doesn't work.

The decompression lever isn't stuck, or partially stuck down is it? This could keep a valve from seating all the way.

Forgive me if I'm repeating this, but you confirmed the injection pump is in the governor fork via the inspection port?

 

[Captainscall]

It could be it, but you never know. The missing washer would delay timing & cause it to inject fuel late, making combution late & half-assed while the valve is opening. These engines are very robust and will try to run in the most adverse conditions. I have seen them run backwards, pulling air in the muffler and smoke coming from the air filter. Mind you, this is terrible as the oil pump doesn't work.

The decompression lever isn't stuck, or partially stuck down is it? This could keep a valve from seating all the way.

Forgive me if I'm repeating this, but you confirmed the injection pump is in the governor fork via the inspection port?

The decompression lever appears to be working properly.

I have confirmed the injection pump is in the governor fork.

I’m banking on the problem being the missing injector spacer. I will definitely give an update when it arrives next week.

Thanks!!


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[kloppk]

There's no stick in the 831 like the 531 then. ....

Maybe they changed design at some point?

The engine parts TM shows a "stick"


Here are the ones I removed from an 831 I parted out recently

 

[WWRD99]

Maybe they changed design at some point?

The engine parts TM shows a "stick"
View attachment 938308

Here are the ones I removed from an 831 I parted out recently
View attachment 938309

Interesting! Mine is just a plug on the 531. So from my motorcycle days do you screw in the stick to get the level or just pop it in without screwing it in. I ended up draining the oil and getting a proper measuring cup to get mine right. Dang thing smoked for at least 30 minutes after that still. I was burning a lot of oil.

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[2Pbfeet]

Interesting! Mine is just a plug on the 531. So from my motorcycle days do you screw in the stick to get the level or just pop it in without screwing it in. I ended up draining the oil and getting a proper measuring cup to get mine right. Dang thing smoked for at least 30 minutes after that still. I was burning a lot of oil.

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In my Yanmar manual the illustration is for the dipstick just resting at the threads, I.e. not screwed in, the L100 Yanmar part number is 114699-01760. I don't know if it crosses over to the L70, but I believe the same cap was used on all L-series engines.
Available on e-bay for about $10, or from Yanmar for $25 or so.

FWIW: Here are the Yanmar instructions.

 

[WWRD99]

In my Yanmar manual the illustration is for the dipstick just resting at the threads, I.e. not screwed in, the L100 Yanmar part number is 114699-01760. I don't know if it crosses over to the L70, but I believe the same cap was used on all L-series engines.
Available on e-bay for about $10, or from Yanmar for $25 or so.

FWIW: Here are the Yanmar instructions.
View attachment 938321

That's gold right there!! It's been years since I got the oil level wrong in mine so I can't remember how much I put in it. Having a stick would be nice though!

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[Ray70]

The decompression lever appears to be working properly.

I have confirmed the injection pump is in the governor fork.

I’m banking on the problem being the missing injector spacer. I will definitely give an update when it arrives next week.

Thanks!!


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My You said you can't pull start without using the decompression lever, that would point towards the compression and valve sealing being at least "acceptable" I personally have never seen a diesel have this type of issue due to a missing or leaking copper washer. You will loose a very slight amount of compression without it, and it definitely needs to be there, but I don't think this is your main problem.

 

[kloppk]

...Having a stick would be nice though!

You are welcome to one of the take outs I have. Probably about $5 shipping.

 

[Captainscall]

Update.

Just got the copper washer. Installed it and it made no difference. Through all the troubleshooting on this machine actually nothing has made a difference at all. The only thing I have not done is replace the injection pump or check the pump timing. There was one shin under the injection pump and I removed it just to see what would happen. It made no change either. This one might just have to sit aside until warmer weather because I am very lost and just can’t figure it out.


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[WWRD99]

Update.

Just got the copper washer. Installed it and it made no difference. Through all the troubleshooting on this machine actually nothing has made a difference at all. The only thing I have not done is replace the injection pump or check the pump timing. There was one shin under the injection pump and I removed it just to see what would happen. It made no change either. This one might just have to sit aside until warmer weather because I am very lost and just can’t figure it out.


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Did you drain the oil yet just to see it's not over filled?

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[WWRD99]

You are welcome to one of the take outs I have. Probably about $5 shipping.

I appreciate that 100%. Unfortunately mine runs great but doesn't make power so it's yard art now. Only 71 hours on it too. Kinda sad.

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[Captainscall]

Did you drain the oil yet just to see it's not over filled?

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I have not drained the oil yet. It reads perfect on the dipstick and is below the threads so I don’t think it’s over full.


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[2Pbfeet]

Update.

Just got the copper washer. Installed it and it made no difference. Through all the troubleshooting on this machine actually nothing has made a difference at all. The only thing I have not done is replace the injection pump or check the pump timing. There was one shin under the injection pump and I removed it just to see what would happen. It made no change either. This one might just have to sit aside until warmer weather because I am very lost and just can’t figure it out.


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Sorry to hear that you are still having issues. I feel your pain. As I mentioned earlier, I had a basically unnoticeable air leak on the inlet to the IP that gave me very similar overfueling grief. And, yes, I was pulling my hair out trying to figure out what the issue was, too. The only fix was to replace the pump as it was a crack on the pump itself.

Replacing the IP is straightforward, just follow the procedure and make sure that the governor yoke engages the IP pin.

When you checked the valve clearances, did you check for a bent tappet.) Have you checked that the timing is approximately right, and the correct valves are opening?
(I knew someone who had a Yanmar that the prior owner had put in a starter that was the wrong starter model and it was spinning the engine backwards. It didn't run very well, but it did run... Apparently, Yanmar makes a CW and a CCW starter for different engine versions.)

All the best,

2Pbfeet

 

[2Pbfeet]

Dumb question, but are you sure that the intake is completely open and there isn't something whacko like shop rag or something stuck in the intake?