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  1. #11
    New Member
    Join Date
    Sep 2010
    Posts
    7
    Tractor
    JD F935

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    How does that governor work? is it not allowing it to come up to enough RPM to smooth out?

  2. #12
    Silver Member
    Join Date
    Oct 2005
    Posts
    223
    Location
    Gisela, AZ
    Tractor
    yanmar 1110d ,fx28d

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    did you ever pull the muffler and try running it?

  3. #13
    Elite Member Car Doc's Avatar
    Join Date
    Mar 2009
    Posts
    3,246
    Location
    Kansas
    Tractor
    YM3810D Yanmar

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    Can you get to the injectors very easy?

    Reason I ask is if it was mine I would get set up to crack injector lines tools rags etc then start it and while its still missing and quick start cracking lines and try to figure out which cyl is affected but thats me.

    The other thing that comes to mind is valve adjustment one could be tight on most Yanmar the setting is .006 thousandths inch cold dont know what that one is but that setting should work, the idea is making sure none are tight... loose is always better.

    Reading your earlier posts on compression they are waaaaaay low so if those were true readings I dont even know how its running??? One more thing is rings they sometimes will not seal until the engine runs a bit when they are worn out or the ring grooves are worn so that may also be an issue.

  4. #14
    New Member
    Join Date
    Apr 2011
    Posts
    4
    Tractor
    John Deere F935

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    Himark,

    Did you ever get this issue resolved?

    My F935 is doing the exact same thing. It will fire right up, but run really rough for a minute or two, then the speed comes up and it smooths right out, and the throttle has no effect while it is running rough. Other than that it seems to be running fine.

    Thanks
    Steve

  5. #15
    New Member
    Join Date
    Jun 2012
    Posts
    9
    Location
    Newtown, PA
    Tractor
    Bobcat Ransomes 25hp 61ZTR, (past JD214) JD 455, Craftsman GT 5000

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    Quote Originally Posted by cincigp View Post
    Himark,

    Did you ever get this issue resolved?

    My F935 is doing the exact same thing. It will fire right up, but run really rough for a minute or two, then the speed comes up and it smooths right out, and the throttle has no effect while it is running rough. Other than that it seems to be running fine.

    Thanks
    Steve
    Hello Zombie post from 2011~ I am no expert, but I would say the OP's problem is an out of adjustment fuel shutoff solenoid.

    On the other hand:


    The compression test, check, specs on a 3TNA72 are:
    Compression pressure 355 PSI or 2448 kPa
    Max diff between Cylinders; 71 PSI or 490 kPa
    Minimum cranking speed 250 rpm

    The part number for the JOHN DEERE GAUGE ASSEMBLY is JT01682, and the ADAPTER is JDG472.

    Googled, searched and searched and THIS THREAD was the closest I could find. Sorry it's so old.

    next to do the compression check on my 3TNA72 and post it on YouTube.

    zero

  6. #16
    Member
    Join Date
    Jan 2007
    Posts
    32
    Location
    Indiana
    Tractor
    John Deere 4005, John Deere F935

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    Did anyone figure this issue out? I have the same problem. Starts easy but will run rough for a minute or two, then smoothes out and will start and run fine until it has a day or so to cool back off. Then, same thing all over again. Also, though it runs smooth when warm, it does seem to lack some power. Kind of sounds like a cylinder compression issue from what I have read. I checked the fuel solenoid and fuel delivery system as far as the injection pump inlet, and that is fine. I don't have the ability to check compression of the cylinders or high pressure injection pump. I plan to take it into a shop after the season is over, but would be nice to have some idea what's going on and how much it might cost.

  7. #17
    Member
    Join Date
    Jan 2007
    Posts
    32
    Location
    Indiana
    Tractor
    John Deere 4005, John Deere F935

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    I finally had to take mine to the dealer. They never really did figure it out...a new injection pump for the F935 still would not cure my problem. They happened to have a F915 on the lot, and when they put the pump from the F915 on it, that worked. So they ordered a new F915 pump for mine and it works great. They can't tell me why, but they noticed the block of my Yanmar is painted green, whereas the rest is black. They said it should be all black, so maybe someone swapped pieces of two yanmar engines together or something strange like that. I got it at an auction, so I didn't know the history.

  8. #18
    Elite Member zzvyb6's Avatar
    Join Date
    Dec 2006
    Posts
    2,740
    Location
    michigan
    Tractor
    jd 1070

    Default Re: Yanmar in a JD F935 mower problems compression 155#

    Mine was doing this until I put a new fuel pump into it. The old pump was barely able keep sufficient pressure up and leaked down pressure to the water separater /filter. The new pump (from O'Reilly Auto Parts) was so strong, it aggravated the age hardened plastic fuel lines in the tank. A crack formed and the pump sucked air when it reached the crack(s). This happened on both tanks. After pulling the tanks and replacing the fuel pickup hoses inside the tanks, the machine is back to full power and starts on demand even it today's weather. I interpreted the rough running as a miss caused by air in the injector line.
    There is no "I" in team, but there is a "Me" if you want to jumble it up a bit...

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