Mep 831A load issues

[grywitt]

@grywitt Did you clean the engine off?

The cooling fins look brand new. (As in 24hrs new, so believe the hour meter.)

I think that getting really black oil out of an engine isn't super unusual- if it has a bunch of hours on it. The carbon never really comes out of the sumps in my experience. (So don't believe the hour meter)

That raises the question to me of how does one get a machine that runs at 1/2 its rated output (+/-) and has a bunch of carbon in the oil if this is a new engine? (Believe the hour meter)

The inconsistency that I see is that even though there is debris in various places in your unit, the fans and fins look really clean, as does the muffler insulation, wires, etc. To me, that argues for the hour meter is probably in the ball park. The oil argues for either much higher hours, or yes, something more serious like broken rings, or damaged valves or valve seats, or the valve guide seals are missing, or something like the decompression lever is always at least partially engaged, or there's half a rag behind the engine preheaters. I think that it is running too well for the camshaft not to be correctly aligned, but it might be possible. When you turn the engine over by hand, is it easy or hard to turn over? Without the decompression lever, this should be pretty darn stiff. If it is hard, I'd take the head off and look for foreign material.

No matter what, I'd button down the fuel lines first.

If you prime the set with the output of the Racor into a clear jar, can you see bubbles? Or do you have a segment of clear fuel line that could temporarily go between the last Tee fitting and the injection pump? It might be a quick test for bubbles. You may be looking for 1/16th inch sized bubbles, so I find a bright flashlight helps. If you find bubbles, I think that means hunting down the leak. If you have bubbles, if it were me, I would go from the tank to the injection pump and disassemble and clean the threads and barbs, checking for debris, and then use a good diesel thread sealant on the threads. Because this engine is so persnickety about air leaks, I prefer to use the style of hose clamps that don't have flat spots at the tightening mechanism. (I couldn't really see the defect that you were concerned about on the injector, but as you have clear hose, if it were me, I would lift the hose up and see if the bubbles accumulate, or move downstream.)

My bet at this point, if the compression is low, would be on broken rings, but I'd be open to something odd. Carbon issues in a twenty hour Yanmar is more than unusual, so something is amiss.

Sorry for the long post, but even if the engine were poorly fueled (overfueled), I have trouble spinning a scenario that lays all of the blame on an air leak and gets the oil to be that dirty, though the better performance on the segregated fuel return suggests that there is an air leak, even if it doesn't cause 100% of your issues. If it had just been SeaFoam, the subsequent test should have been better and they weren't.

I am open to any critiques. All new fuel lines more pics coming. I used pipe dope on all the tees. Used clamps that crimp. Doubled some clamps where the barb was long enough. I was very careful not to get pipe dope beyond the threads into the line.

 

[grywitt]

I am open to any critiques. All new fuel lines more pics coming. I used pipe dope on all the tees. Used clamps that crimp. Doubled some clamps where the barb was long enough. I was very careful not to get pipe dope beyond the threads into the line.

I also filled the filter with sea foam and ran the pump for a while. The when I bumped the start button it started before one revolution. ( it seemed anyway) with it starting that easy or would think the timing should be correct hu?
Any way i ran it for a minute or two now I'm letting it sit for a while before I test it again. That's today so far. Thanks for watching. Ha ha

Well nothing changed. That's a lie it does have all new fuel lines. The last two pictures I think might show the problem. Certainly not helping. I'm a little embarrassed that I had pulled it out once but apparently didn't hold it the right direction to see the bend. My bad. I guess now I know why I had to adjust the valves both times I checked them. This is the exhaust valve pushrod. Well I'm not a diesel mechanic but I'm learning. I ordered new push rods. Should I be looking for further damage besides this? Should I pull the head and clean the combustion chamber or just try to burn it out once I have new push rods?

I hope this is the problem. It could make sense of the issue.

 

[2Pbfeet]

I also filled the filter with sea foam and ran the pump for a while. The when I bumped the start button it started before one revolution. ( it seemed anyway) with it starting that easy or would think the timing should be correct hu?
Any way i ran it for a minute or two now I'm letting it sit for a while before I test it again. That's today so far. Thanks for watching. Ha ha

Well nothing changed. That's a lie it does have all new fuel lines. The last two pictures I think might show the problem. Certainly not helping. I'm a little embarrassed that I had pulled it out once but apparently didn't hold it the right direction to see the bend. My bad. I guess now I know why I had to adjust the valves both times I checked them. This is the exhaust valve pushrod. Well I'm not a diesel mechanic but I'm learning. I ordered new push rods. Should I be looking for further damage besides this? Should I pull the head and clean the combustion chamber or just try to burn it out once I have new push rods?

I hope this is the problem. It could make sense of the issue.

TAAADAAA! Congratulations.



I hope that this fixes it for you. Yes, new tappets and proper valve settings should do a lot for the engine performance.

Nice job on the hoses.

I am sorry that it so long to surface the bent tappet, but to me a bent tappet would explain the bad valve clearance you noted at the beginning, the fact that it changed on you, the inability to maintain load, the black oil, and the signs of the overfueling. Nice to have a consistent problem, though the separate fuel lines does argue for the set having had a small air leak as well. When you do get the new tappets in, and if the machine is running ok, I'd change the oil one more time on the bet that there is unburnt diesel as well as soot washed down into the oil.

FWIW: at least in my experience with these engines bending tappets often seems to happen when the valve clearance is either too tight, and can't handle the differential thermal expansion, or surprisingly, (to me at least), if the valve clearance is too large, as the tappet seems (I guess) to bounce around and get hammered by the closed rocker arm.

All the best,

2PbFeet

 

[grywitt]

TAAADAAA! Congratulations.



I hope that this fixes it for you. Yes, new tappets and proper valve settings should do a lot for the engine performance.

Nice job on the hoses.

I am sorry that it so long to surface the bent tappet, but to me a bent tappet would explain the bad valve clearance you noted at the beginning, the fact that it changed on you, the inability to maintain load, the black oil, and the signs of the overfueling. Nice to have a consistent problem, though the separate fuel lines does argue for the set having had a small air leak as well. When you do get the new tappets in, and if the machine is running ok, I'd change the oil one more time on the bet that there is unburnt diesel as well as soot washed down into the oil.

FWIW: at least in my experience with these engines bending tappets often seems to happen when the valve clearance is either too tight, and can't handle the differential thermal expansion, or surprisingly, (to me at least), if the valve clearance is too large, as the tappet seems (I guess) to bounce around and get hammered by the closed rocker arm.

All the best,

2PbFeet

Thank you again for the help. I'm hesitant to get to excited that's the problem but it sure does seem like the right disease for the symptom. I do like the new fuel lines. Would you take the head off and have a look or just put the new pushrod in and try it? The Yanmar book says not to go any further than you have to.

I'm not sorry it's taking so long. I'm way less intimidated by that motor than I was. I needed that. I'm learning tons. The times I've learned the most as an electrician are when I'm getting my but kicked. I really do hope it's the pushrod though. A win would be good about now. I played with the injection timing. ( meaning I was trying to watch when it pumped fuel while I was turning it) I didn't actually try to adjust anything. It looked petty right to me.

One more thing. The Rocker arms look discolored like they have gotten very hot. Is this pretty normal and should I be concerned? The pads where they push on the valve look good and except for the color change they look great.

 

[2Pbfeet]

Thank you again for the help. I'm hesitant to get to excited that's the problem but it sure does seem like the right disease for the symptom. I do like the new fuel lines. Would you take the head off and have a look or just put the new pushrod in and try it? The Yanmar book says not to go any further than you have to.

I'm not sorry it's taking so long. I'm way less intimidated by that motor than I was. I needed that. I'm learning tons. The times I've learned the most as an electrician are when I'm getting my but kicked. I really do hope it's the pushrod though. A win would be good about now. I played with the injection timing. ( meaning I was trying to watch when it pumped fuel while I was turning it) I didn't actually try to adjust anything. It looked petty right to me.

One more thing. The Rocker arms look discolored like they have gotten very hot. Is this pretty normal and should I be concerned? The pads where they push on the valve look good and except for the color change they look great.

I think it never hurts to get familiar with an engine that you might depend upon. I think that these Yanmar engines are neat engines, but that's me.

In general, I'm with the Yanmar manual; stop digging when you hit dirt.

That said, yes, I think that the valves got unburnt diesel and soot sprayed up by the valve guides by the looks of that, but it might also be some heat; how does the underside of the valve cover look? From here, the rocker arm contact surface looks ok, as I would expect. If it were me, I would be tempted to take a wire brush to the rocker arm to see if discoloration is superficial or not. Also, I would probably inspect (have a look-see at) the valve stem itself and the area around the top of the valve guide, without removing the springs. At this point, I haven't seen anything that would cause me to go as far as pulling the head, but other may see something that I missed.

Diesels are designed to burn lean, so even a little over fueling due to poor injection spray (e.g. air leak) can get them pretty hot pretty fast. The head and exhaust pipe looked ok from here.

All the best,

2PbFeet