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  1. #1
    New Member
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    John deere

    Default Yanmar injection pump modifications

    I have been wondering the vast lands of google looking for some answers on my yanmar injection pump, I've seen some threads on here before that have been created by very knowledgeable mechanics so I thought maybe i could ask them a few questions and TAh DAH here I am. Ok now that's out of the way here we go, I have a Yanmar 3TNE68 I am modifing for garden tractor pulling and I have hit a dead end on what I could do. This engine was donated to me for this purpose with the sole request to see what it's capable of so I'm not afraid of blowing it to pieces. So here is what I've got done so far, i have advanced the timing 3 degrees. I have the fuel screw backed all the way out and the rpm limit screw done the same I tacked it at 4420 rpm. I also have a fuyan SJ-44 turbo on it that makes 8-10 psi of boost. The turbo is too big for the engine so I'm trying to build the engine up to the turbo if that makes any sense. My biggest problem is I need more fuel. With the pump already at its current limit I'm not sure what to do. One guy told me to send it to Columbus Diesel along with $2,000-$3,000 as he did his but I don't have that level of money to dump in this thing. So here is my big question I know the injection plungers and barrels are easily removable in this engine so could I swap out the plungers from a larger engine like a 3TNE84 with an inline pump? I've tried to find out if they are the same but with no luck. If I can get more fuel to it I plan on porting and polishing the head and having a cam reground for it. Any help is greatly appreciated.

  2. #2
    Elite Member
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    Default Re: Yanmar injection pump modifications

    Good luck with that.

  3. #3
    Super Member California's Avatar
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    Sonoma County
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    Yanmar YM240, and now just one YM186D

    Default Re: Yanmar injection pump modifications

    That engine sounds like it is headed for a short, spectacular life.

    Please post videos!

  4. #4
    Elite Member
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    gilmer tx
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    Bobcat CT235

    Default Re: Yanmar injection pump modifications

    Hmmmm! No help here but welcome the the forum.

  5. #5
    Gold Member
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    Default Re: Yanmar injection pump modifications

    The pump housing is machined to accept THOSE sized P&B's..
    P&B's from an inline wont work.. they're much larger & wont fit the bore.
    Depending on what pump you have, it IS possible to get more fuel at top end but your going to run into low idle problems..
    It wont idle.. & possibly wont shut off..
    What I'm talking about is moving the control rack SEGMENTS, 1 tooth OR if you have the adjustable type, that's even better.. you could just adjust the fuel to "more".. & still maintain your shut-off position..
    BUT, you'll need a calibration stand for that..

  6. #6
    Platinum Member Scotty Dive's Avatar
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    Yanmar 2020D

    Default Re: Yanmar injection pump modifications

    Not sure this will help, but by here were two pumps....iirc a 7cc and a 9cc pump.
    Thanks,

    Scotty Dive
    Yanmar YM2020D "Git er Done Too"
    Pictures! http://s139.photobucket.com/albums/q...t=dfc00199.pbw
    Yanmar Tractor Database - Click Link, then click file and download the excel file.: https://drive.google.com/file/d/0BxR...it?usp=sharing

  7. #7
    Platinum Member Scotty Dive's Avatar
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    Yanmar 2020D

    Default Re: Yanmar injection pump modifications

    Quote Originally Posted by Scotty Dive View Post
    Not sure this will help, but by here were two pumps....iirc a 7cc and a 9cc pump.
    Never mind...this is for a hydraulic pump
    Thanks,

    Scotty Dive
    Yanmar YM2020D "Git er Done Too"
    Pictures! http://s139.photobucket.com/albums/q...t=dfc00199.pbw
    Yanmar Tractor Database - Click Link, then click file and download the excel file.: https://drive.google.com/file/d/0BxR...it?usp=sharing

  8. #8
    New Member
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    John deere

    Default Re: Yanmar injection pump modifications

    Quote Originally Posted by California View Post
    That engine sounds like it is headed for a short, spectacular life.

    Please post videos!
    At least when it goes it will be in a blaze of glory!

  9. #9
    New Member
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    John deere

    Default Re: Yanmar injection pump modifications

    Quote Originally Posted by thepumpguysc View Post
    The pump housing is machined to accept THOSE sized P&B's..
    P&B's from an inline wont work.. they're much larger & wont fit the bore.
    Depending on what pump you have, it IS possible to get more fuel at top end but your going to run into low idle problems..
    It wont idle.. & possibly wont shut off..
    What I'm talking about is moving the control rack SEGMENTS, 1 tooth OR if you have the adjustable type, that's even better.. you could just adjust the fuel to "more".. & still maintain your shut-off position..
    BUT, you'll need a calibration stand for that..
    Ok so here is my next question, I have access to a CNC shop and what has kept me from just making a set is the insanely tight tolerance between the barrel and plunger (plus or minus 0.0001 and a mirror finish on both) so is the plunger the same just with a larger "piston" and a larger barrel? I can do some machine work on the barrel and housing if the is a chance it will work. I just ordered a plunger of eBay for a 3TNV88 for comparison reasons, it was only $30.00 so if it won't work I'm not out a whole lot. Every one who has already done this either sent it to a professional shop along with 2-3 grand or did it themselves but none will talk about it. I'm just trying a possible alternative.

  10. #10
    Gold Member Bigkrank's Avatar
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    NW Ohio

    Default Re: Yanmar injection pump modifications

    If you are not worried about rules and have a machine shop just adapt an inline pump on it, Bosch A pump or whatever. This has been done for years. It has been about 10 years but was buying 3 cylinder A pumps on ebay with 8 or 9mm plungers, if I remember right, pretty reasonable.

    The guys who got serious with the 78 Yanmars split the blocks in half between the 2nd and 3rd cylinder if I remember right. kubota"s block & bottom ends are built much stronger but you need to convert to direct injection.

    You may also need a charge pump capable of something like 40-50 psi, at least you do if sticking with a cambox style pump.
    Several garden tractor pullers
    Kubota B2630
    Kubota ZD28
    Ford 655D backhoe
    Bobcat T190, various attachments
    Numerous Farmalls

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