Mep 831A load issues

[grywitt]

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Here is the injector spray pattern with the return lines hooked up correctly. I even ran the pump when I put the line on the injector to make sure no air was in it. I used clear line to watch what was happening. I have the braided stuff coming but I'm impatient. I did try it with the fuel lines like they are now with all the return lines installed and no air. Same as before 2kw seems like full load and 3kw acts like 4 and drops rpm then the contact. I will upload that video as well

 

[grywitt]

Not much here just me trying giving it load and trying again. The return lines are full and routed correct. I've never watched the spray pattern of an injector before but from what I've read that looks pretty good right?
Recap. 3kw acts like over load except the time I had the return lines routed wrong. I'm not going to lie I'm a little stumped.

 

[2Pbfeet]

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Here I think is proof and hopefully a clue for someone more knowledgeable than me about these fuel systems. I had bought some 3/16 fuel line down at the auto parts store hoping to temp in and test while I wait for the right stuff. Well the hose was loose on the little plastic tee and my clamps weren't the right size either. I put the gen in run and had leaks.

Any way one thing that confuses me about this return fuel system is the double tee and the fact that it is always putting positive pressure on the return side of the injector. If someone can explain this to me and how it's supposed to work i would love that. I will research and try to learn myself if not. The needing a path for return fuel i get but that part not so much.

Any way I thought if I send the fuel back to tank from the first tee between the two pums and then run another line to tank from post injector for any needing to go there too. I know it's not right and the people that design these things know what the are doing and I'm just not fully understanding yet. But in this configuration the gen held 3kw it wasn't running right exactly but it didn't bogg down and die.

I took this video and tried to show what I did and what the governor was doing also. I had lost that little tee but I've found it now but I think i will order one or two anyway.

If this helps someone know what's going on with the gen that would be awesome. Right now I plan on ordering the right fuel line and clamps and keep digging

View attachment 951788

That video with the return fuel line not connected and SeaFoam sounds like a much better behaved engine to me. How was the smoke? To me the rerouted fuel lines argues for an air leak. If it were me, I would replace lines and fittings, and look carefully for any fuel weeps. (Brake cleaner, dry, then run)

From what I can see, the injector pattern looks fine to me.

Once you get the various lines sorted out, if it were me, I would be tempted to run it for a few hours at 2kW, then 2.5kW, and then see if you can creep up closer to 3kW. I would try to stick to the highest level that it can maintain without smoking too much. You may need to burn some carbon out.


All the best, 2PbFeet

 

[grywitt]

Thanks again. I didn't read your response before i tested the injector spray. Oops. I appreciate the explanations though. I'm running it with load now like you suggested.

 

[Guyfang]

To answer the injector test question, yes, that's sort of how to do it on the machine, but I would do something so you aren't spraying diesel into the muffler insulation. Just sayin... Personally, I like to have the injector clear of the engine, but rags or pig blankets work, too. I've seen others modify a clear plastic jar to accept the injector, and capture the diesel.

On some diesel engines, the injectors will pass significant quantities of diesel, sometimes because they use the pressure in the diesel to further increase the pressure in the spray. This engine passes very little diesel beyond the injector ("the return" side, though strictly speaking it is really leakage). Since that "return" line is basically injector lubrication bypass weep, I am of the opinion that a few psi of back pressure is basically round off error at the injector.

You would need to ask someone more experienced with the history of this generator why the fuel lines were plumbed the way they were. (@Guyfang- any thoughts?) All I can come up with is that someone was trying to avoid a fuel tank penetration. Well, this set was meant to be simple, (Ha, Ha) in that respect. So Yes, that could be the reason why.

Yes, SeaFoam might have helped. If I were a betting man, I'd bet that the fuel line was leaking a little air, and perhaps still is leaking a little bit of air. I've seen so many of these units have that issue. In my experience, Yanmars just don't run well if there is even the tiniest bit of air getting into the injection pump, or in the high pressure line. This seemed to be my biggest problem with the YANMAR engine. Any leak, or trapped bubble, was a PITA. On the MEP-831A, if the fuel line is good and the fittings are clean and tight, it does work as designed. A more typical Yanmar motor design runs that injector weep line all the way back to the fuel tank, so an air leak on the line is not an issue and uses fewer in line fittings.

 

[grywitt]

See this little rough spot on the injector return line connection? Could that be a problem? I would think i would see any air with the clear lines. I have better stuff coming and I ordered an injector just in case.

 

[grywitt]

This oil looks as dark as the last and it has about 2.5 hours. Rings? I don't see metal but that is really sootie for 2 hours that filter is behind that valve so I need to raise the engine to take it out?

 

[grywitt]

I decided to try to take the exhaust off to look inside as suggested. It's really buried. I got the side off and then the pull cord assembly. The more I look at it I think it will be easier to take down the bank wall than to move the motor.

I ran the motor for some hours at 2500 watts and if anything it got worse. Still 2kw seems to be about as high as can go without smoke and rough running. Then I drained the oil and it was black and sootie after only a couple hours of running. I did try once more to run it with the return lines routed like the one time I could hold 3kw. It didn't repeat so I think the sea foam in the filter did more than the return line routing.

So I'm trying to get the exhaust off and I will be able to dig into the top end deeper if needed. I am open to any suggestions of where to go from here. I guess since I have the side cover off I can verify injection timing. Any tricks on the best way to get that exhaust off would be greatly appreciated. I got two bolts off that are tucked underneath it and I'm not sure i can get them back in without digging deeper now. Ha ha.

I'm learning the machine so that's nice!!
Hope everyone is having a great weekend.

 

[2Pbfeet]

@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.

Does this make sense?

All the best, 2PbFeet

 

[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.

Does this make sense?

All the best, 2PbFeet

Yes it does. Thank you for taking the time to give such a thorough explanation. When I tried to pull start it between dead batteries and the way I've got it now with batteries outside the unit. The compression lever had popped up from me pulling to get pressure. I ended up pulling the generator towards me about a foot so pretty stiff I would say.

I've got fuel lines and clamps and tees ordered I'm going to give it all new fuel lines. Are any of the tees anything but tees? I was thinking of changing them too. That engine is really crammed in there. The TM doesn't address the getting to these areas from what I can find.

Thanks again for Gary

 

[2Pbfeet]

Yes it does. Thank you for taking the time to give such a thorough explanation. When I tried to pull start it between dead batteries and the way I've got it now with batteries outside the unit. The compression lever had popped up from me pulling to get pressure. I ended up pulling the generator towards me about a foot so pretty stiff I would say.

I've got fuel lines and clamps and tees ordered I'm going to give it all new fuel lines. Are any of the tees anything but tees? I was thinking of changing them too. That engine is really crammed in there. The TM doesn't address the getting to these areas from what I can find.

Thanks again for Gary

Yes, that sounds like reasonable compression.

Well, IIRC, there is a shift in tubing sizes, so you need to account for that, e.g. a reducing/expansion port on one tee, but otherwise, yes the tees are tees. You can check the TM for part numbers and details. I think that the downside to a nice compact TQG is that, yes, everything is tucked in. Comes with the territory in my book. I'll take an TQG over an open frame generator anytime I need to use one, and remind myself of the upside when I'm servicing them.

All the best, 2PbFeet