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  1. #1
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    Jinma 254

    Default Jinma 254 Blowby Compression Testing

    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

  2. #2
    Platinum Member sd455dan's Avatar
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    Default Re: Jinma 254 Blowby Compression Testing

    Quote Originally Posted by gromitbeast View Post
    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
    Last edited by sd455dan; 04-21-2013 at 01:09 PM.

  3. #3
    Veteran Member Bob Rooks's Avatar
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    Yuchai Bulldozer

    Default Re: Jinma 254 Blowby Compression Testing

    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.
    Yuchai 306R dozer, Mustang 2040 skid steer, Mitsubishi MS035 Mini-Ex with four buckets and a rake, Trimble equipped 7' Dual Dozer with twin GCR-2 laser receivers, and a LiTW BH7600 back hoe (sold).

  4. #4
    Platinum Member sd455dan's Avatar
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    Default Re: Jinma 254 Blowby Compression Testing

    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?for...13665580452137 think it works now

  5. #5
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    Jinma 254

    Default Re: Jinma 254 Blowby Compression Testing

    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

  6. #6
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    Jinma 254

    Default Re: Jinma 254 Blowby Compression Testing

    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

  7. #7
    Platinum Member
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    Default Re: Jinma 254 Blowby Compression Testing

    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.

  8. #8
    Platinum Member sd455dan's Avatar
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    Default Re: Jinma 254 Blowby Compression Testing

    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...
    Last edited by sd455dan; 04-26-2013 at 02:42 AM.

  9. #9
    Veteran Member Bob Rooks's Avatar
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    Default Re: Jinma 254 Blowby Compression Testing

    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.
    Yuchai 306R dozer, Mustang 2040 skid steer, Mitsubishi MS035 Mini-Ex with four buckets and a rake, Trimble equipped 7' Dual Dozer with twin GCR-2 laser receivers, and a LiTW BH7600 back hoe (sold).

  10. #10
    New Member
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    Default Re: Jinma 254 Blowby Compression Testing

    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.

    -p5010152-jpg-p5010153-jpg-p5010154-jpg-p5010158-jpg-wp_20130425_002-jpg

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