YM226D Project

[tc197]

Pulled the injectors back out this afternoon and attempted to check the compression. I am getting 280psi on the cylinder furthest forward and 250psi on the middle and rear cylinders. According to my service manual, 426 is considered the low where it becomes hard to start so that may explain part of my struggles. Could I be doing something incorrect when checking compression that would give a lower result or is it pretty black and white and I need to look into an overhaul/rebuild?

I checked the rods and linkages the other day and didn't see any issues. I attempted to look at the governor mechanism but apparently I am missing a section in my manual and it wasn't clear to me what to check so I left it alone for now. Now that the injectors are out again, I will test the spray patterns when I get a chance.

 

[winston1]

About a 300 rpm speed is needed for compression check. A good starter and battery should provide that. Probably did but might pull all three injectors while checking one cylinder at a time.

 

[CoyPatton]

I second Winston’s suggestion of pull all 3 injectors (label them in a manner that you know what cylinder they came from for diagnostic purposes) then rerun your compression test. A slow turning engine is often difficult to start.
This is one of the reasons that most import Yanmars have a decompression lever on them.
Prior to tear down, I would spend more time in assessment of what is going on. Bore scopes can provide lots of info without removing the head from the engine. Also check the valve clearances.

 

[bmaverick]

I second Winston’s suggestion of pull all 3 injectors (label them in a manner that you know what cylinder they came from for diagnostic purposes) then rerun your compression test. A slow turning engine is often difficult to start.
This is one of the reasons that most import Yanmars have a decompression lever on them.
Prior to tear down, I would spend more time in assessment of what is going on. Bore scopes can provide lots of info without removing the head from the engine. Also check the valve clearances.

Coy, You are so right. I've made it a full habit to PULL the decompression cable no matter what season to start the engine. The less hard starts the longer engine life.

In fact, I used that decompression cable so much, the plastic mount to the dash panel broke. I've posted here how I remedied the fix.

Hope to hear from tc197 soon!

 

[tc197]

Just to be clear I'm doing this right:
- Disconnect fuel lines and fuel return lines
- Pull all 3 injectors (label/keep track of which cylinder they go in)
- Insert Hoye compression adapter in place of injector. I am placing the adapter on top of the fiber washer and holding it centered while I secure it in place with the injector retainer. The adapter is a smaller diameter than the injector.
- Connect compression gage and place throttle in full rearward (off) position.
- Crank the engine over, ideally looking for 300rpm and record compression reading. Should I be using the decompression lever in my compression test to get the speed up, or are you strictly mentioning that for starting purposes?

On a side note, I tested the injector spray patterns this morning and all three look pretty good in my opinion. I held some cardboard about 3 inches away and all three sprayed about a 1" circle of fuel onto the cardboard.

Thanks for the help guys, really appreciate it!

 

[runningbird]

don't pull the decompression lever for the test

 

[tc197]

don't pull the decompression lever for the test

Thanks runningbird.

Using the process I just mentioned above, with no decompression lever, my results were 305psi, 250psi, 255psi.

I have not checked valve clearances before - on this tractor or in general - so I will go read up on that process. Thanks CoyPatton.

 

[tc197]

All States Ag Parts | Used & New Tractor, Combine & Skid Steer Parts

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Seems pretty straight forward, I'll give it a go

 

[tc197]

Valves didn’t appear to be way off, although I’m not sure how much they would need to be off in order to notice a difference. Regardless, I adjusted them all to .007-.008 using a feeler gauge set and followed the process in the procedure linked above.

I rechecked compression after playing with valves and got the same results.

We have a lot of rain coming tomorrow so I wanted to button things back up. While I was putting the injectors in I must have overtightened the retainer and ended up cracking one and causing a small split in another. Lesson learned and I’ll have to find some replacement retainers.

 

[winston1]

All States Ag Parts | Used & New Tractor, Combine & Skid Steer Parts

All States Ag Parts is the leading supplier of tractor, combine, and skid steer parts to North America. Shop for new aftermarket, remanufactured, and used tractor parts.

www.hoyetractor.com

 

[CoyPatton]

Personally I like using a leak down test to attempt to determine where my issue is at.
Simplified—you use compressed air to simulate compression, then check to see where the loss is going.
1 & 2) air hissing in exhaust or intake (1
& 2) loss points
3) Air hissing from oil pan (dip stick tube)
4) bubbles in coolant
5) air hissing from around valves with cover off
6) air hissing from oil passages

These give you a very good ideal of what is worn the worse in the engine.
Also bore scopes have gotten fairly inexpensive and can give good info before a tear down begins and reduces those OH CRAP! moments when you pull the head.

 

[bmaverick]

Personally I like using a leak down test to attempt to determine where my issue is at.
Simplified—you use compressed air to simulate compression, then check to see where the loss is going.
1 & 2) air hissing in exhaust or intake (1
& 2) loss points
3) Air hissing from oil pan (dip stick tube)
4) bubbles in coolant
5) air hissing from around valves with cover off
6) air hissing from oil passages

These give you a very good ideal of what is worn the worse in the engine.
Also bore scopes have gotten fairly inexpensive and can give good info before a tear down begins and reduces those OH CRAP! moments when you pull the head.

Would you also recommend taking the radiator cap off or the overflow cap to see if bubbles start happening like a fish aquarium ? It may show if the head has issues, thus needing a new head gasket or other re-work.

I like your method of detection very much.

 

[tc197]

Personally I like using a leak down test to attempt to determine where my issue is at.
Simplified—you use compressed air to simulate compression, then check to see where the loss is going.
1 & 2) air hissing in exhaust or intake (1
& 2) loss points
3) Air hissing from oil pan (dip stick tube)
4) bubbles in coolant
5) air hissing from around valves with cover off
6) air hissing from oil passages

These give you a very good ideal of what is worn the worse in the engine.
Also bore scopes have gotten fairly inexpensive and can give good info before a tear down begins and reduces those OH CRAP! moments when you pull the head.

Thanks CoyPatton, that process makes a lot of sense. Mind helping me clarify a couple of details?

1. What PSI should I be using for testing purposes? Will 50psi get it done? 100? Just need to determine if I have to borrow a big compressor or if I can make do with what I have.

2. Can I use my compression injector adapter that I purchased from Hoye to connect to the compressor instead of the compression gage?

3. Any recommendations on a borescope? I've used one at work in the past but it was a high end laboratory grade unit with articulation. Does the harbor freight 75$ unit seem reasonable or is there something with a bit more bang for the buck out there?

Edit: It just popped into my head that the autoparts stores may loan these borescopes out and it looks like they do. I may try that option before purchasing.

Edit 2: Autozone had a borescope as part of their loaner program. Went and picked it up this morning. As long as I return it within 90 days they don't charge anything - can't beat that!

 

[CoyPatton]

Would you also recommend taking the radiator cap off or the overflow cap to see if bubbles start happening like a fish aquarium ? It may show if the head has issues, thus needing a new head gasket or other re-work.

I like your method of detection very much.

Either should work assuming the cap holds good pressure, but I prefer the radiator cap.

 

[CoyPatton]

I have always had access to a compressor that generates 100+ psi so I don’t know about about 50 psi, low psi may not seep past the pressure building up to 250 compression test levels.
As for fittings, sorry not much help.
With a borescope, you may be able to tell your issue. A valve that is burnt, or doesn’t close, a burnt piston head, damaged cyl walls. I would check that out first.

 

[bmaverick]

I have always had access to a compressor that generates 100+ psi so I don’t know about about 50 psi, low psi may not seep past the pressure building up to 250 compression test levels.
As for fittings, sorry not much help.
With a borescope, you may be able to tell your issue. A valve that is burnt, or doesn’t close, a burnt piston head, damaged cyl walls. I would check that out first.

Most of the stand-up Porter-Cable compressors reach 125psi and can do this compression leak down.

 

[CoyPatton]

Most of the stand-up Porter-Cable compressors reach 125psi and can do this compression leak down.

I think a 30 gal tank with a 100+ psi capability is about as small as I have ever used. It was a upright roll-around compressor with an oilless unit on it that a buddy owned that I used at his place. It worked, but I don’t know specifics about it at this point. Wild guess on tank size and psi, although 100psi capability is fairly common.
One think I can assure you of, is a slightly opened valve can deplete a 60 gal tank quickly.
The pressurization process of compression is very different than the pressure of a leak down test so there is not a need to match the psi for the leak down test, I just don’t know about 50psi forcing past weak seal points that still hold 250psi in a 450psi+ design cylinder.

 

[tc197]

Unsuccessfully tried to use the borescope today. I realized pretty quick when trying to insert it down the injector hole that the pre-combustion chamber is still in place. The borescope is much too big to fit through any of the holes in the chambers and the chambers seems to be pretty well stuck in there. Searching online it seems most people take the head off and knock them out from the back. I'm leaning closer to just pulling the head and diving in, but I'll do some more searching first.

 

[tc197]

Im doing some research on compression and leak tests. Im having trouble coming up with the connectors and adapters required to connect a compressor to the injector adapter - but in my searches I found people discussing wet vs dry compression tests.

Dry compression testing is what I already did. A wet compression test is done by adding a small amount of oil into the cylinder on top of the piston before checking compression. The results of the wet test, in theory, can help point to the source of the problem. If compression is higher in the wet test, chances are the rings are not sealing well and may need to be replaced. If compression doesn’t change, it points to valves or head gasket.

Any thoughts on me attempting a wet compression test to try and further diagnose the issue? I think its a step in the right direction in case I can’t get a leak down test put together.

 

[bmaverick]

Im doing some research on compression and leak tests. Im having trouble coming up with the connectors and adapters required to connect a compressor to the injector adapter - but in my searches I found people discussing wet vs dry compression tests.

Dry compression testing is what I already did. A wet compression test is done by adding a small amount of oil into the cylinder on top of the piston before checking compression. The results of the wet test, in theory, can help point to the source of the problem. If compression is higher in the wet test, chances are the rings are not sealing well and may need to be replaced. If compression doesn’t change, it points to valves or head gasket.

Any thoughts on me attempting a wet compression test to try and further diagnose the issue? I think its a step in the right direction in case I can’t get a leak down test put together.

What grade oil? 15W40 that is thick or SAE 30 being a tad thinner? 5W30 may be useless to test with wet.