Oil & Fuel Jinma 254 Blowby Compression Testing

[gromitbeast]

Hey Guys,

Happy to be a new member of what appears to be a great forum. I have recently acquired a JM-254 circa 2001 with a Y385 engine. I appear to be getting some blowby characterized by loss of power under load and smoke coming out of the crankcase breather. Tractor does start and run. The tube connected to oil fill on the valve cover is sucking and free from obstruction. From my research on this forum and CTOF it appears that my most likely candidates for this are stuck/bad rings on one or more of the pistons or a crack in the block. Before tearing everything apart I'd like to test compression. I suspect that pulling the glow plugs and testing compression there is my best bet. Can anyone help me with the following questions:
1. Am I missing any obvious or easy troubleshooting steps here?
2. Are there any best practices or known procedures out there for running a compression or leakdown test on these. Anyone know what the glow plug threading is?
3. What sort of pressure should I see? Specification on Y385 is 22:1 so I'd expect 22 atm or 323 psi or more right? Anyone have practical experience on this value?
4. As long as I'm pulling the glow plugs for compression testing I plan to replace them and the sealing rings? Manual says model 1055 Part No. Y480G-12200 it also calls it the "A Shrouded Electrothermic or Preheat plug 10-12-65, 12V" I'd sure like to cross these to a locally supplied champion, ngk or autolite part number anybody have some advice on how to do that? I've tried calling napa, autozone, etc with no success

Thanks for your help!

Nick M
Illinois

 

[sd455dan]

Hey Guys,

Happy to be a new member of what appears to be a great forum. I have recently acquired a JM-254 circa 2001 with a Y385 engine. I appear to be getting some blowby characterized by loss of power under load and smoke coming out of the crankcase breather. Tractor does start and run. The tube connected to oil fill on the valve cover is sucking and free from obstruction. From my research on this forum and CTOF it appears that my most likely candidates for this are stuck/bad rings on one or more of the pistons or a crack in the block. Before tearing everything apart I'd like to test compression. I suspect that pulling the glow plugs and testing compression there is my best bet. Can anyone help me with the following questions:
1. Am I missing any obvious or easy troubleshooting steps here?
2. Are there any best practices or known procedures out there for running a compression or leakdown test on these. Anyone know what the glow plug threading is?
3. What sort of pressure should I see? Specification on Y385 is 22:1 so I'd expect 22 atm or 323 psi or more right? Anyone have practical experience on this value?
4. As long as I'm pulling the glow plugs for compression testing I plan to replace them and the sealing rings? Manual says model 1055 Part No. Y480G-12200 it also calls it the "A Shrouded Electrothermic or Preheat plug 10-12-65, 12V" I'd sure like to cross these to a locally supplied champion, ngk or autolite part number anybody have some advice on how to do that? I've tried calling napa, autozone, etc with no success

Thanks for your help!

Nick M
Illinois

Not sure on the actual cylinder compression readings-Bob Rooks may be able to help, as for the electrothermic plug, I just replaced mine on a Shanghai tractor the part was only about $20 plus shipping I'm sure Affordable or Circle g or Farm Boys can help- that's where I got mine...But the others can help to...


OH and WELCOME to TBN

 

[Bob Rooks]

Welcome Nick.
You should see about 350 - 400 psig on an engine at operating temperature. 300 - 350 psig cold engine. In either case, no more than 15 psig differential between cylinders as this creates a power imbalance and wreaks havoc on the crankshaft and bearings. A leakdown test, which you probably already know, will tell you which is worse - rings or valves.
Undoubtedly, you will have to make your own adapters from either a glow plug or an old injector.

 

[sd455dan]

gromitbeast I re read your post and think i may have given you bad advice about the elecrothermic plug ,I checked my Invoice and believe the same nomenclature is being used for a heating only glow plug and a fuel type electothermic plug. my part # for the fuel type(it has a fuel connected as well as switched 12 volts) isGLW-cT26 fits TY-395, 495A,4100 engines'
The main thing with the electro thermic unit I listed is there is only one, and it is mounted at the beginning of the intake manifold..and also has a diesel fuel line attached to it. From your description the type you want is a true glow plug that heats the combustion area and mounts in the head and you have 1 for each cylinder with no fuel connections. i would call Tommy
Affordable Tractor Sales
http://api.viglink.com/api/click?fo...ales Company&jsonp=vglnk_jsonp_13665580452137 think it works now:thumbsup:

 

[gromitbeast]

Hey Guys,

Thanks for the welcoming words and the information. I think I'll see if I can't slap a tester on there to help with the diagnosis a little bit. I guess I'm out of luck for an easy standard/locally available glow plug.

Bob - Thank you for those pressures! Exactly what I was looking for. I guess I've have to fabricate the right adapters.
sd455dan - Thanks for the info on the glow plugs and calling in Bob for the pressures.

I'll post an update once I run some compression tests.

Regards,

Nick

 

[gromitbeast]

Hey Guys,

Here's the current update:
1. I bought the Harbor Freight Diesel compression tester ($30). To my delight it came with a properly sized adapter for the glow plugs on my Y385.
2. I did a cold compression on each of the cylinders. #1 - 520 psi, #2 - 420 psi, #3 - 400 psi
Excessive compression on #1 was certainly not what I was expecting but could be a good thing...At this point I'm starting to think that the exhaust valve on my #1 cylinder is not opening properly causing incomplete combustion. The compressed gases in #1 are finding an alternate route out of the cylinder and into the crankcase which would explain my power loss and my smoke coming out the crankcase breather. I'm going to pull the valve cover off and have a closer look. Any other ideas as to why I might be seeing excessive compression are welcome!

Thanks,

Nick

 

[Rich Waugh]

It would seem to me that the compression readings should not be high due to a valve - both valves are supposedly closed at the time of full compression, right? The only way to get a reading higher than theoretically possible would be if there was partial combustion during the test or if the volume of that cylinder was somehow reduced, say by heavy deposits or something similar. If there is no possibility of partial combustion (complete combustion would go off the scale, I would think), then I'd have to say that the high reading is "normal" and the other two cylinders are low.

BUT - (and this is a BIG but), I'm no expert on diesel engines and could be off in left field with my interpretations here. Bob Rooks will undoubtedly have more reliable advice.

 

[sd455dan]

One thing that stands out about that engine, is the 22 to one cr that is -at least from the tractor specs I have looked at , on the upper end of the range for these smaller Chinese diesels... I agree with Rich about a possibility of some deposits?? built up in the pistons compression bowl.. reducing the volume
I guess if the exhaust valve was staying closed you could possibly see higher than normal cranking compression, also there would be no where to (exhaust the combustion gasses and particulates- resulting in a decreased chamber volume and increased blow by. I would pull the valve cover and roll the engine over and observe the valve opening and closing and check out the #1 exhaust closely and then check and set your valve clearances hopefully reveal something...
If that exhaust valve isn't opening, can't imagine what that diesel sounded like when running but imagine one heck of a racket, I believe a giveaway of a closed exhaust valve problem with #1 that you can see at this time would be a whole bunch of carbon build up on cylinder#1s glow plug but not the others ???
Another way that valve can stay closed or not open like it should would be a (wiped) cam lobe, bent or broken damaged,push rod(cam follower/clearance adjuster) for exhaust valve one...

 

[Bob Rooks]

Did you remove all the injectors except for the cylinder you are testing, because that will make a difference in cranking speed. The glow plug holes aren't really big enough to evacuate the cylinder volume properly. You should also put three or four squirts of motor oil into each cylinder just prior to testing it.
Are you by any chance running the engine for testing? That is another type of test called firing pressure, but not usually performed on these engines, and requires different equipment.

 

[gromitbeast]

Hey Guys,

Bob, Rich and sd455Dan Thanks for the replies and info it was helpful in further diagnosis and determining my path forward! I thought I'd check in with you all again.
Rich - What you say makes sense.
Sd455Dan - Good points, adjusted lash, though pretty large adjustment was needed I saw no improvement. It certainly is making one heck of a racket while running which I supposed I failed to mention in
my original post! No major carbon buildup on #1 vs other cylinders though. Visually the valve travel looked ok while cranking with the valve cover off...
Bob - I did not remove all injectors that's a good point about speed and volume through glow plug holes too, all glow plugs were removed for all tests though. I tested again with oil squirt and same
results. Engine is not running during tests.

So here is what I've done:
Head
After some additional testing (leakoff > 25% in each cylinder, adding oil (per Bob R), adjust valve lash, etc.) I decided to pull the head. Upon removal I noticed the head gasket was in pretty bad shape (see pictures) and it looks like there may have been some cross flow between cylinders 1 and 2. I brought the head into a performance shop to get it magnafluxed and they suggest reface, and exhaust valves, guides, seals. I went ahead and ordered those as well as intake just to do a complete valve job as long as I was at it. Ordered up valve parts and head gasket / valve cover seal from Affordable and hoping to get them later this week.

Block
A bit of carbon built up on all cylinders and some dings on top of the pistons in all cylinders makes me think something nasty got in there and maybe tore up the head gasket a bit (pictures below). I've polished up the block surface with a wire brush and there does not appear to be any cracks or pitting or anything nasty. Cylinder sleeves look pretty good and tight...

Fuel
I also gave the fuel tank a thorough cleaning and there was some pretty nasty looking stuff in there. The intake filter and the wire mesh filter in the petcock were completely disintegrated. While I wait for parts/head maintenance I'm going to build my own pop off tester and try to balance my injectors having a hard time crossing from the high pressure line on the injector to 1/4 NPT but it looks like the ORB threading might do the trick. For glow plugs I've found some glow plugs (NGKY107V) that appear to pretty closely cross over (threading is perfect, length is about right, wattage slightly different see photo). I guess I'm a risk taker so I'm going to risk it and try using them (at $6 / piece v. $25 / piece for the Jinma ones I'd sure like to make these work)

Some pictures below. I'll update again once I have everything back together for a trial run. Fingers crossed.

 

[Willl]

and some dings on top of the pistons in all cylinders

Just a bit

Deep gouge in #3 or just a dark spot ?

 

[sd455dan]

Looks like a few pieces of (something) got past the air cleaner- and the mention of blow by, and the rotted head gasket..

Well other than the head work and new gaskets , my main worry would be ring damage, or the ring lands in the piston... from whatever was bouncing around in those cylinders- and your mention of a fair amount of blow by , screams ring seal or ring damage to me...Yet the overall compression #s are not that low...
if it were me I would pull the pistons and replace the rings and hone the cylinders as a minimum...I would also check the blocks surface straightness, under aprox. .002 " hopefully ,
Little bit confused, lots of blowby, 25% leakage ,but no change with the addition of oil?

Normally introducing oil when there is ring leakage will bump up the #s- that didn't happen.. which tends to point to valve /seat seal.. but valves do not cause blow by...

But whatever was rattling around had to get out somehow, past the exhaust valves and seats usually.. now that would increase leak down.
The blow by still bothers me I would dig a little deeper... :2cents: also looks like you are well on the way to getting the Jinma fixed :thumbsup:

 

[quicksandfarmer]

My armchair mechanic opinion: It looks to me like the pitting was caused by coolant entering the cylinder and boiling, which would be expected when the head gasket fails. I think all of your problems were caused by a head gasket failure, very common with this engine.

 

[Bob Rooks]

IMHO,
The liners look glazed. This can be from high engine hours or running with a dirty air cleaner that has channeled, and/or dirty (heavily sooted) engine oil. The liner on the right appears to have vertical marks (scoring?) which would indicate broken piston rings. How much of a ridge is there on the liners?
Yes, you can still have decent compression with broken rings, and conversely you can have a lot of blow-by with good rings if your valve guides are badly worn.
When you did the leak-down test, did you put your ear to the intake manifold, the exhaust, and the crankcase breather for each cylinder to get an idea of how much air was escaping from each area?
And I can definitely tell from the red/orange coolant passages that this engine has been subject to very poor maintenance practices.

 

[sd455dan]

My armchair mechanic opinion: It looks to me like the pitting was caused by coolant entering the cylinder and boiling, which would be expected when the head gasket fails. I think all of your problems were caused by a head gasket failure, very common with this engine.

I disagree about all the damage being caused by the head gasket failing. ( not saying some of the damage wasn't done by boiling coolant) -but zoom in on piston # 2- that appears to be mechanical caused damage... I would pull those pistons - it's not that much more work...just to be sure the rings or ring lands aren't damaged... Maybe it is harder than I thought / does the Jinma have a crankcase inspection window so that the rod caps can be pulled???

 

[quicksandfarmer]

I disagree about all the damage being caused by the head gasket failing. ( not saying some of the damage wasn't done by boiling coolant) -but zoom in on piston # 2- that appears to be mechanical caused damage... I would pull those pistons - it's not that much more work...just to be sure the rings or ring lands aren't damaged... Maybe it is harder than I thought / does the Jinma have a crankcase inspection window so that the rod caps can be pulled???

To remove the oil pan you have to split the tractor and pretty much take the engine out, the front wheel assembly bolts to the pan. Some Jinma's have a hatch in the bottom of the oil pan that allows limited access to the bottom of the engine so you can replace the oil pump without splitting the tractor. Mine doesn't have the hatch, so I don't know if you can detach the pistons (and more important, re-attach them) that way.

Instructions for splitting the tractor are in this thread:
http://www.tractorbynet.com/forums/...35-jinma-304-tractor-running-low-2-print.html

 

[quicksandfarmer]

Here's a picture of what the oil pan with the hatch looks like:
Engine sump pan

Looking at that, I think you could possibly remove the pistons with the oil pan on (and the engine still attached to the tractor).

 

[sd455dan]

Here's a picture of what the oil pan with the hatch looks like:
Engine sump pan

Looking at that, I think you could possibly remove the pistons with the oil pan on (and the engine still attached to the tractor).

I see what you mean. If the OPs style does not have a removable bottom inspection cover, it means pulling the whole front half of the tractor apart...

 

[gromitbeast]

Hey Guys,

Thanks for all the great feedback. Valves, etc came in this week and I dropped them off to be installed on the head once it's re-faced. As you guys all mention rings are a high concern for me. I got optimistic at the mention of the inspection port by quicksandfarmer. I was expecting if the rings are shot than I'll need to split the tractor. I went out and looked but no luck on the inspection hatch on my model.

I need to send some updated pictures with head surface and block surface scraped off...it doesn't look as bad after all that old rotted gasket material is removed.

Bob, I'm in full agreement on the poor maintenance practices. I just recently picked this tractor up at what I thought was a steal (may still be if I can get her running right). We shall see though. I did use a stethoscope to try and pinpoint noise during the leakdown but could only really hear anything @ the intakes.

I have a week long out of town trip coming up this week which is OK because I'm still waiting on some more pieces to come in to check injector pop off and for the head to get finished. I plan to put it all back together next week and see how it run with new gasket, valves, etc. If I'm still getting poor performance and blowby I fear splitting and rings/sleeve are my next move (fingers crossed that I won't have to do that!)

Thanks everyone for the great discussion and valuable input. I'll update again in a week or so.

-Nick

 

[gromitbeast]

Hey All,

I'm back. Sorry for the long lapse, life took over for a while and the tractor had to be put on standby. After a lot of cleaning/replacing of parts, sanding of surfaces, etc. I got it all back together today after doing the following:
- New Head Gasket
- Near intake and exhaust gaskets
- New glow plugs
- New #1 injector (took it apart like a dope and cheaper to buy a new one than to re-calibrate)
- New Temp Plug Housing (over-tightened the temp sensor and cracked it...geez)
- Thoroughly cleaned head, machined flat and tested with new valves, collets, guides
- New valve cover gasket
- Fresh valve lash adjust, head re-torque
- Cleaned radiator and fuel tank, new fuel filters (in tank and in bowl). Lots of crud in fuel tank with in tank filter completely destroyed

The result...NO Improvement. Still hard starting, crazy loud knocking, lots of blowby (indicated by smoke coming out crankcase breather) and a lack of power. A few other notes:
- After a lot of cleaning I noticed what appears to be a very small crack in the block between cylinders 2 and 3.
- Running temp on cylinder 1 appears to be ~100 F lower than #2 and #3 (running at ~200 F on #1 vs. ~300 F on #2 and #3) Checked with Infrared Thermo on exhaust manifold

So I'm stuck thinking I need to do the following:
- Split the tractor (appears to be on the order of several days worth of work for a shade tree mechanic like me based on what I'm reading at: Benye Tractor with Yangdong Diesel Engine | CHINESE TRACTOR OWNERS CLUB FORUM)
- Replace cylinders, sleeves, rings and probably the block (note crack above) (~$1,700 in parts) or the entire engine (~$3,000)
- Pray i can re-assemble and pray again that it runs

Or...give up, cut my losses and see if somebody wants to buy as is...I'm seriously considering this option.

Advice and ideas are welcome!

Thanks,

Nick