YM186D Compressiontest

[ajaukema]

Hello, we have a bad starting YM186D (3t72HA).

Done a COLD compression test cilinders reach, cil 1: 280PSI , cil 2: 285PSI , cil 3: 300 PSI.
First stroke about 100PSI
Second stroke about 150 PSI
Third stroke about 200 PSI
Then it takes another 4-5 strokes to 280-300 PSI
Then Cold wet compression test, it takes less strokes to build the max pressure but not a significant higher pressure.

Also done leak test (cold & dry) at TDC, this is at around 85 PSI air pressure.
Cil 1: 35% loss
Cil 2: 35% loss
Cil 3: 15% loss

35% is nog great but not really bad I think

Plan to do a hot compression test, but starting is about cold engine.
Once it is hot, its start reasonable.

Cleaned the injectors by ultrasonic cleaner, does not improve the starting.

Want to test the injector but I need to find/create an M14/M12 adapter first.

Consider to take the head of.

Lap the valves, check piston rings.

It is hard to get new liners over here.

I think maybe the liners, pistons and rings are worn.

Not shure about the injectors (sprainpattern, pressure, leak) yet

What do you think on these compression values?

Regars,
Albert Jan

 

[etpm]

It is hard to get new liners over here.

Wherever here is.
Eric

 

[California]

Does the starter spin it fast enough?

When my YM240 needed a starter I replaced it with a gear-reduction starter spec'd for a much larger Yanmar. Same teeth etc but 2kw replacing the stock 1.2 kw.

That cranks the engine frantically fast. I expect it would add several years troublefree starting, to a worn out engine.

 

[ajaukema]

An update:

Injectors
-Cleaned the injectors
-Opening pressure > OK
-Not leaking just below opening pressure > OK
-Spray pattern > OK

Head
Took the head of; lots of carbon on the valves and valve seats
-Cleaned head and valves
-Lapped the valves as best as possible (lots of pitting).
-Checked leakage, head upside down and put thinner on top > OK
-Checked leakage, head upside down, put water on top and applied pressed air into intake and exhaust ports > OK

Liners
-Measurement top and bottom, crossed, within tolerance > OK
-Honing marks still in sight (assume not glazed)
-Few small vertical scratches

Pistons
-Cleaned
-Measurement diameters within tolerance >OK
-Put new rings on it

Starter
Maybe not the right one, not sure at the moment.

Fuel
- New filter
- Cleaned all fuel lines

After all this the engine is not better at starting then it was before. If it runs it is still smokey.

Did a new compression and leakage test on Cyl 3 in cold condition.

-Leakage at TDC 10%, carter
-Compression 300 PSI in 4 strokes, 350PSI after 8 strokes

Will test the other cylinders too.

 

[ponytug]

Hello, we have a bad starting YM186D (3t72HA).

Done a COLD compression test cilinders reach, cil 1: 280PSI , cil 2: 285PSI , cil 3: 300 PSI.
First stroke about 100PSI
Second stroke about 150 PSI
Third stroke about 200 PSI
Then it takes another 4-5 strokes to 280-300 PSI
Then Cold wet compression test, it takes less strokes to build the max pressure but not a significant higher pressure.

Also done leak test (cold & dry) at TDC, this is at around 85 PSI air pressure.
Cil 1: 35% loss
Cil 2: 35% loss
Cil 3: 15% loss

35% is nog great but not really bad I think

Plan to do a hot compression test, but starting is about cold engine.
Once it is hot, its start reasonable.

Cleaned the injectors by ultrasonic cleaner, does not improve the starting.

Want to test the injector but I need to find/create an M14/M12 adapter first.

Consider to take the head of.

Lap the valves, check piston rings.

It is hard to get new liners over here.

I think maybe the liners, pistons and rings are worn.

Not shure about the injectors (sprainpattern, pressure, leak) yet

What do you think on these compression values?

Regars,
Albert Jan

It seems as if you have made progress. Has this tractor always been hard starting, or is this a new behavior?
What color is the smoke?
Once started, how does it idle? How is the power at maximum throttle? How hot does the exhaust get when working at maximum throttle for ten to fifteen minutes under load?

All the best,

Peter

 

[ajaukema]

As long as I know it is a bad starter and it is getting worse every year. The tractor is used daily but short time and has no heavy load, only transport. Thats a good recipe for carbon buildup

At the moment Im not sure if the bad start and smoke are two different problems or just the same.

Smoke when running is dark, hard to say it is blue (oil) or black (diesel).

During winter first smoke is white (unburned diesel)

If it runs it idles ok except smokey.

Not sure how the tractor performs hard working for a longer time.

 

[Gjamtrac]

As long as I know it is a bad starter and it is getting worse every year. The tractor is used daily but short time and has no heavy load, only transport. Thats a good recipe for carbon buildup

At the moment Im not sure if the bad start and smoke are two different problems or just the same.

Smoke when running is dark, hard to say it is blue (oil) or black (diesel).

During winter first smoke is white (unburned diesel)

If it runs it idles ok except smokey.

Not sure how the tractor performs hard working for a longer time.

Sounds like you have done all the right things except; have you checked your valve clearances.
Yanmar published a mistake back about the time the YM186 was being made and said .006" clearance, they corrected it to .008" cold at TDC.
Where are you located?

 

[winston1]

For what it is worth, this is the compression specs for the YM220/222. A little larger than yours but I feel it would be real close to your 186. Specified pressure 568 to 639 psi. Lower limit 426 psi.

 

[ponytug]

For what it is worth, this is the compression specs for the YM220/222. A little larger than yours but I feel it would be real close to your 186. Specified pressure 568 to 639 psi. Lower limit 426 psi.

Great point.

I do wonder how severe the valve seat pitting that @ajaukema mentioned is. With new rings and the correct ID sleeves with limited scoring, that leaves pretty much the valves and springs for low compression. In my experience, Yanmar normally has pretty stiff springs compared to other makes.

All the best,

Peter

 

[ajaukema]

Sounds like you have done all the right things except; have you checked your valve clearances.
Yanmar published a mistake back about the time the YM186 was being made and said .006" clearance, they corrected it to .008" cold at TDC.
Where are you located?

Forgot to mention, valve clearance is set to 0.2 mm as dictated in the manual and is shown on a sticker on the engine.