MEP-831A - Huge amount of exhaust smoke

[zapp]

Hi -

Hoping you guys can share any insights. I picked this up through GP and just got around to trying to start it. It had been drained of all fluids so I PM'd it and went to try and start. It fired up, however, there was massive smoke flowing out of the exhaust. I also noticed the governor was resting on the magnet while it was running which I thought should have killed the motor. I got it shutdown but wondering if this is a crack somewhere in the block letting engine oil into the firing cycle, valves, or something else? Anybody see this before? I took a video to help visualize below.

https://youtube.com/shorts/r1ZeYZRuUFE?feature=share

Thanks,

Steve

 

[2Pbfeet]

Hmmm... that looks like oil from here. Does it clear up at all? If not, have you checked the entire intake path to make sure there isn't something plugging it up?

If it doesn't clear up, I would wonder about valve guides or rings being an issue, or even a cracked head, but I would check the air intake first. It is very easy to pull the head.

All the best,

2Pbfeet

 

[zapp]

I thought it looked like oil too with the amount of smoke. I let it run and there is so much smoke that I shut it down - doesn't seem to clear up. Would a bad fuel injector pump cause this type of issue (dumping too much fuel)? I wouldn't expect this level of heavy smoke though?

 

[2Pbfeet]

Unburnt fuel looks very different; usually either clouds of white smoke (uncombusted fuel) or "rolling coal". Personally, with diesel engines, I have found that it is helpful to become proficient in the different colors of smoke and their possible causes as it can really speed up the diagnostics. A quick search of the archive here and/or the internet should get you lots of pictures and videos.

If the smoke didn't clear, I'd follow the TM, but I would have a look see at the entire intake first. Then it is the usual TM steps. I do think that the return fuel line being Teed into the inlet line for the injection pump does increase the chances of air in the high pressure side which causes all sorts of instabilities for these Yanmar engines in the '831. If you have any doubts about the hoses, I would preemptively put new hoses in. I consider it a "pay now / pay later" thing, and personally, I don't want my generators to fail when I need them.

All the best,

2Pbfeet

 

[uniquify]

When you added oil, did you fill it from the top (valve cover cap) or from the bottom (dipstick hole)?

 

[zapp]

From the bottom dip stick. I wondered since the unit had been drained of oil/fuel when I got it if someone put oil in the top thinking it was for long term storage benefit and maybe that is what is going on?

I was thinking based on 2bfeet recommendations, I'd try the following to see if I get any better understanding of what is going on:

1/ Pull air filter and look for obstructions
2/ Looks for any fuel leaks/perforations which might cause air in lines.
3/ Bleed fuel line and confirm no air.
4/ Look at IP and see if anything is out of whack.
5/ Pull valve cover and check valve measurements.

If nothing jumps out, start a more detail TM walk through.

 

[FarmingSmallKubota]

The way its running wide open also sounds like the governer gear is broken or when someone replaced the injector pump they did not get the lever lined up with the fork through the peep hole

 

[2Pbfeet]

From the bottom dip stick. I wondered since the unit had been drained of oil/fuel when I got it if someone put oil in the top thinking it was for long term storage benefit and maybe that is what is going on?

I was thinking based on 2bfeet recommendations, I'd try the following to see if I get any better understanding of what is going on:

1/ Pull air filter and look for obstructions
2/ Looks for any fuel leaks/perforations which might cause air in lines.
3/ Bleed fuel line and confirm no air.
4/ Look at IP and see if anything is out of whack.
5/ Pull valve cover and check valve measurements.

If nothing jumps out, start a more detail TM walk through.

In my limited Yanmar experience, it is unusual for an L70 engine to stutter or stumble the way yours is doing, and @FarmingSmallKubota's suggestion of the injection pump not being engaged properly, or with a bent pin/rack would certainly do it. That is an easy check; remove the inspection plate and look.

If you can, try to use a borescope to look all the way to the intake valve. I sometimes think generators get put on the back shelf as "inoperable" due to issues that are so basic that everyone looking at it didn't consider it, and afterwards folks didn't have the time/manpower to go back to square one to find it.

If you do pull the valve cover, I'd check that the valve clearances are in specifications, and that the tappet rods are straight and not bent. I have seen valves in specification, but with a bent tappet rod, and the engine did not run well at all. I'd have a look in the injector port with the borescope as well, just to rule out debris.

I believe that the 831s have the more complex Yanmar sealing on the valves, but I could be wrong. If they do, it is easy to generate a leak if not all of the parts of seals are put in, or not put in correctly. (I have worked on the L-series engines, but not on an 831.)

All the best,

2Pbfeet