MEP016D Starting Issues - Grrrrrrrr...

[stoneburner]

So, I've had my MEP016D for nearly 10 years. It has been with me through a derecho and countless other power outages. got it with 1 hour on the meter (if I remember correctly). It has always started on the second pull, even in freezing weather...until now.

I've kept up with maintenance, and it's currently at 120 hours, last time it was run was in July or August this year. Ran started and ran perfectly fine at that time.

Went to start last week and nothing. I was exhausted after fighting for 1/2 hour to start. Since then, I have changed the fuel filter, verified fuel flow/pump operation, tested the injector pattern (good), nothing. Air filter is still good. I even tried an ether shot or two. Not even a sputter.

Then, I realized that I didn't almost break my wrist when I forgot to hit the decompression valve several times. In fact, no difference between compression valve/no compression valve. Diesel mechanic neighbor suggested pouring cap full of oil directly into the cylinder to see if I had a "dry" piston. No improvement in compression. I'm about ready to shoot this thing with my M1 Garand. But, I've been down that road before and I always regret taking my frustrations out on my equipment. Unless it deserves it. I know this HAS to be something stupidly simple. Maybe? Only 120 hours. What could be wrong? I'm leaning toward valve(s) being carbed up, but before I take the cylinder head off, I wanted to see if anyone else has had this sort of thing happen with their Yanmar L70AE diesel. And what resolved the problem?

Thanks!

Mike

 

[Dieselmeister]

before I take the cylinder head off, I wanted to see if anyone else has had this sort of thing happen with their Yanmar L70AE diesel. And what resolved the problem?

Thanks!

Mike

I would take off the valve cover, and check the valve clearances before tearing the engine apart. Thats only two bolts. Maybe a valve is stuck open. Just be careful not to damage the gasket when you pull the cover off.

 

[DieselAddict]

Yep, take the valve cover off and check for s stuck valve.

 

[stoneburner]

Oh, Yah...didn't mention that part of the investigation. Once I knew I had fuel, I pulled the valve cover off and slowly pulled the cord. Rocker arms rocking and valves are operating (nothing stuck). I also checked valve clearance and the intake valve was good at 0.15, and the exhaust valve was a bit over - but not much - so I went ahead and adjusted back to 0.15 as well. The decompression valve is also operating normally. So all seems normal under the valve cover.

This machine has sat around a lot, obviously, with only 120 hours on the meter over 10 years. It's been a great machine up until now. On average, I'd say it gets fired up for a few hours every 3-4 months. Something has happened in the past four months since the last time it ran... just don't know what.

 

[DieselAddict]

With that new info I would recommend pulling out the injector and blowing some air in the cylinder with it at TDC on compression stroke to see where its leaking its compression.

 

[Ray70]

I had a similar issue on a 16D someone brought me to repair. It was running during a storm then died during the night.
He was able to restart and ran another hour and died again. Now it would barely sputter a little.
After checking everything possible I found that he was unaware the machine had an oil "strainer" ( not really a filter )
The strainer was totally plugged with carbon and junk.
Long story short he lost oil pressure which spun the rod bearing. The spun bearing wore down the crank journal.
Together these 2 factors effectively lowered the piston to deck height at TDC thus drastically reducing compression to the point it would no longer ignite the fuel.
You can easily pull the head ( gaskets can be reused ) bring it to TDC and rock the crank back and forth and look for excessive crank rotation before piston moves, or use your hand to check for play in the rod bearing.
Even try rotating by hand with head on. rock back and forth and listen for a slight clunk when changing direction of rotation.

 

[stoneburner]

I didn't even think of compressing the cylinder with air. Definitely going to give that a shot before I pull the head...Thank you for that advice!!

As far as the strainer, I had mine out and cleaned at last oil change. It was in good shape each time I've pulled it, with very little fouling..but I'm glad you brought that up and I will definitely be paying more attention to it (I was not aware of myself for the first couple oil changes). If I end up pulling the head, I will be checking for excessive play. Hopefully nothing that drastic. And thanks for letting me know these aren't necessarily single-use head gaskets! I had been looking for a replacement. I'll have some time to mess with it more this weekend.

Thanks for all of the advice!

Mike

 

[stoneburner]

So, here's the latest in the MEP016D saga...

I rotated the engine to the point where both valves were closed. I am assuming that it was at the top of piston travel. Had my compressor set to 60 psi, and applied pressure with a pipe wrench on the crankshaft to keep it from turning (took off the recoil starter). It held air, with no sign of leakage. I then turned the crankshaft (not sure exactly how much, but it was about half way between valves opening each direction), I am assuming the bottom of the stroke. At this point, after putting pressure in the injector port, I had air rushing up past the pushrods. Which doesn't sound good...

So, my amateur thoughts are that I have air leaking past the pistons (this doesn't make 100% sense to me because I'd think that it would be leaking at the top of the stroke, too) or I have a bad head gasket? Thoughts? Or does it sound like it could be something else?

I do recall seeing vapor coming out of the oil filler hole after I removed it after cranking several times. I have no experience with small diesel engines like this, so any advice at this point would be appreciated!

Thanks, y'all...

 

[DieselAddict]

Sounds like you have internal engine damage. You'll need to tear it down to get the rest of the story I'm afraid.

I'm guessing you have an issue where the piston is moving too far down the bore or you have a crack in the bore.

 

[stoneburner]

I was afraid that might be the case. Nothing is ever the "simple" fix! Well, I'll be pulling the head to see what's going on first chance I get. I feel like this machine is worth putting some money into - what are your thoughts on that? But still can't figure out why I'd have a failure like this at relatively low hours. I'll report back once I have some more info. This might be outside my comfort zone for repairing.

 

[Dieselmeister]

This might be outside my comfort zone for repairing.

Don't let that stop you. You currently have an engine that does not work. If you are careful when you disassemble it, you can't make it any worse. Taking the head off is the first and easiest step. Take plenty of pictures when working on it, that way you have something to look at when reassembling it. These engines are rather easy to work on. All the parts and manuals are available. That's why I have 4 generators with these engines - They are reliable and easy to maintain. Think of it as a diesel powered lawnmower engine.

 

[Ray70]

Before you get too discouraged and before tearing the motor down do 1 more thing....
So you say you have compression leaking at or near the bottom of the stroke, but not at the top, there is actually a good explanation for this.
There are at least 3 factors that contribute to this:

When the engine is simply sitting there the rings are essentially sealed to the cylinder wall due to their pressure against the cylinder wall, but what is sealing the rings to the piston?? NOTHING! They are just floating around in the grooves.
The movement of the piston actually plays a big part in sealing the rings to the piston grooves, as does the combustion pressure.
As a 2nd check, do your test again. put the piston at the bottom where you had the air leaking the most, give the motor a slight bit of rotation, just enough to put a little pressure trying to drag the rings upward, thus putting some pressure between the sides of the rings and the sides of the piston grooves and see if your air leak decreases. If it does, you may have a perfectly normal piston bore.

The 2nd reason for leakage at the bottom is that a normal cylinder is tapered out at the bottom resulting in lower piston tension than at the top.

The 3rd reason is that right at the bottom of the stroke the rod changes direction and causes the piston to cock slightly sideways as the direction changes.
rotating the engine slowly by hand may leave the piston slightly crooked if you are right near the bottom of the stroke, all the more making an air tight seal between the rings and piston nearly impossible

Bottom line, you don't have quite enough information yet to say for sure that you have a cylinder bore problem.
Either test it a little bit more, or tear into it, either way it needs to get fixed.

 

[Dieselmeister]

Just thought of another thing to try before tearing anything apart. You have fuel, and air, but not enough heat to light off the fuel. Try heating the cylinder and air intake with a heat gun or hair drier, to the point that they are uncomfortable to touch, then, while blowing hot air into the intake (take off the air filter), try starting it. It might just work. That's how we used to start an old tractor in cold weather, when it didn't want to go.

 

[Ray70]

Good thought, I have had to do that on my Lull a couple times when it was really cold out, but he already tried starting fluid and that wouldn't even sputter.
These motors are so simple to take apart, I think we're closing in on tear down time....
One other question for Stone Burner... it sounds like you were kicking your own ass trying to start it, and it sounded like using the rope starter only??
Does your machine have an electric starter on it??
Rope start definitely isn't getting you the RPM ( and compression / heat ) that you would get with the starter motor, although it should still start with the rope, unless it is super cold in Ohio now??

 

[Guyfang]

The basic gen set, the MEP-016A and its other variants, did not come with a starter. There was an option to (later in the 80-90's) to put one on, but few people did, or were allowed. And after the solid state ignition MWO came out, starting the gasoline engine was so easy that no one bothered with it. Then came out the Yanmar engine MWO. That came with a starter, BUT, some installations of the MWO were done without a starter, but very few were not brought up to standards at a later date. So yes, this set should have had a starter.

 

[stoneburner]

Indeed, this genset is equipped with an electric starter. I have never used it, mainly for two reasons:

1. This particular engine has always started with the recoil starter, even in the coldest of temperatures. My last oil change was in February 2021, and I remember that time. It was COLD outside - like teens or single digits. She fired up with the second pull if I remember correctly. Last attempt was this past saturday - temperature was in the 60s. Not even a sputter.
2. This is a 24v starter, and the only 24v DC source I have is my M35A2. Getting that thing close enough to run jumper cables would be a nightmare. I never wanted to mess with batteries just because they've been completely unnecessary. Then there's the expense in buying batteries and maintaining them. All for a few uses each year.

Something has changed since the last use a few months ago. Maybe I didn't cool down long enough? Maybe a manufacturing flaw in the cylinder liner finally gave way? Who knows. I have not pulled the head yet, but it looks like a pretty quick and simple thing to do to allow for a visual inspection all along the full piston stroke. If warm enough next friday or saturday, I plan to do this.

Do you guys think that it would be worth the effort to try to crank with the starter? I'd have to take the switch panel off and then unwire the NATO plug to jump the leads directly from my deuce batteries. There's compression, but not like I remember...

 

[DieselAddict]

You can try using the starter but if it has so little compression that you can pull the recoil starter without the compression release I don’t think it would start.

 

[Ray70]

I wouldn't bother. If it has always started easily in the past and now it doesn't even sputter with ether in it, not to mention hand cranking without releasing the decompression valve, why bother? Something is wrong internally.
Just bite the bullet and take the head off, it will actually be faster than rigging up jumper cables!

 

[stoneburner]

Three months later, and I finally found time to pull the cylinder head off my my machine. Took about 20 minutes. Seem like warm days always had family functions, and I was left with cold days...like today. So, here are my observations:

- I did not see any discoloration on the cylinder wall
- There was still horizontal cross hatching visible on almost all of the wall, with more of a mirror polish and some light vertical marks on the front/back of the wall (I think you can see those in the photos)
- vertical "scratches" were not detectable by running my fingernail across them
- I was able to slightly move the piston laterally in the cylinder (and I mean "slightly)
- I was not able to detect any "looseness" of the piston vertically

Any thoughts? I have never messed with a small engine like this - but the vertical "scratching" wouldn't strike me as something that would cause a loss of compression. But, what do I know? I've seen new ring sets for sale; pistons with new rings; 0.050 overbore pistons/rings, etc. I'm trying to figure out the next step. Like I said, never messed with one of these before.

 

[Dieselmeister]

How did the top end and the valves look?
Some ideas for what to do next - (possibly not the best, but easy to do without any special tools):

Set the piston at midpoint, and pour in 1/2 inch of diesel fuel. Then move the piston up and down by turning the flywheel to see if the diesel leaks past the piston / rings.
Next idea would be to bolt the head back on, with the cylinder half full of diesel, (without the pushrods, to keep the valves closed), then try to compress the diesel by turning the flywheel. If there is any major compression leak, the diesel will find the leak, and go there.

Another option would be to fab an adapter to pressurize the cylinder with air, either through the injector port, or exhaust (with the valve open), and listen/feel for any air leaks at the oil fill ports.

My suspicion is that there is a problem with the rings. When the machine was running last, at 3600 rpm, the air/fuel were being compressed fast enough to heat up and detonate, and keep the engine running, despite the small leak. Once the engine cooled off, the compression with the starter rope was too slow to overcome the leak and get hot enough to light off the fuel.