New to me: Kubota D650 15HP

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Harry United States of America
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Re: New to me: Kubota D650 15HP

Post by Harry »

thebuildist wrote: Mon Jun 24, 2024 8:10 pm Well, now I've had the privilege of tearing down and (hopefully) re-assembling an injector pump.

I didn't enjoy it. My British friends would call it "fiddly." Very fiddly.

I couldn't find precisely the correct manual or video for it, but I watched a couple that were consistent enough that I was able to apply the knowledge to this one.

It turns out that each of the 3 "pumping units" are actually small (5/32" or so) precision ground pins reciprocating inside precision honed sleeves. The pin is the piston, and the sleeve is the cylinder.

image.png

The pin has a vertical slot (think keyway) and the sleeve has a hole in its "cylinder wall" near its midpoint. So if the pin is rotated to a certain position in the sleeve, then the "keyway" slot can draw fuel through the cylinder wall hole, and with each stroke a bit of that fuel will be "pushed" upward to the injector. But if it's rotated to a different position, then the keyway is away from the hole in the cylinder wall, and no fuel is pumped.

So the volume of fuel is controlled by rotating that pin.

The pin is indexed inside a gear-toothed collar.

image.png

And moving the control rack rotates that collar.

image.png

So sliding the rack rotates the pins, which causes them to pumpeither a little or a lot of fuel.



But those 1 inch long pins sitting in those 1 inch long sleeves, with maybe a thousandth of clearance were very solidly glued in place. They couldn't move up or down, they couldn't rotate. So the geared collars couldn't rotate, so the rack couldn't slide.

I had to drive the pins down out of the sleeves with a punch. (Delicately). Cleaned everything up, washed it in gasoline, lubed it all up with wd-40, and reassembled everything. Now the pins reciprocate and/or rotate freely. Rack slides effortlessly.

It'll probably be Thursday before I can put it all back together and confirm it pumps when the engine turns over.

Assuming it does, I expect to have a runner!

Bob
Bob your a braver man than I. I would not have the patience to do the fiddly work, plus I’m always saying my hands just don’t work like they use to. I commend you on your patience and workmanship. :thumbsup: :peace: Harry
1973 444, 1974 644, 1976 446, 1977 646, 1986 226
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Re: New to me: Kubota D650 15HP

Post by DavidBarkey »

Well done Bob . I found a place in UK that sell rebuild kits for small deisel injector pumps . I plan on doing the Kubota 2 cyl. in the bride before firing it up.
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Re: New to me: Kubota D650 15HP

Post by Eugen »

DavidBarkey wrote: Tue Jun 25, 2024 6:05 am Well done Bob . I found a place in UK that sell rebuild kits for small deisel injector pumps . I plan on doing the Kubota 2 cyl. in the bride before firing it up.
Please share the link Dave. :wave3:
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Re: New to me: Kubota D650 15HP

Post by DavidBarkey »

https://injectionpumps.co.uk//
Kit came Royal mail. A red jacket with big fuzzy black hat put in a paper air plain and through it hard to Canada .
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Re: New to me: Kubota D650 15HP

Post by JSinMO »

@thebuildist Good work Bob! Should be a nice running engine. Most of my experience is with gas engines but I have seen a run away diesel. They go wide open real fast! @RoamingGnome has a good idea to have something ready to put over the air intake just in case. I’ve seen guys keep a piece of wood bigger then the intake close by for the first start up.
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Re: New to me: Kubota D650 15HP

Post by thebuildist »

Wellllll...

I have bad news.

And worse news.

It's time to point out, "This deal always seemed too good to be true."

Oh well.

I may have mentioned that I bought this on FB from a guy at a shop who works on big diesel trucks. What you might call a "diesel mechanic". I presumed it was at his shop because he had worked on stripping down an old bucket truck, and this equipment came off. It was clearly removed at least partly with a torch.

And he told me, "the guy said it runs fine, but I don't know for sure."

And then it had a drained oil pan. How odd. Even for long term storage, why drain the oil?

Anyway, the bad news is, my reassembled injector pump is only putting out fuel on 2 out of 3 lines. Maybe I got something installed wrong? Or it's not sealing or whatever? I'll have to tear it apart again to see.

But with fuel to two cylinders, it really shimmies over pretty good, and ALMOST starts up.

But that's where the worse news comes in. A really loud clunking noise with every rotation, once it's spinning over pretty fast. It took my ears just a second to analyze it and tell me what it is:

A rod knock. A bad one.

Now it makes sense: THAT'S why it was at a diesel mechanic's shop. THAT'S why the oil had all been drained out of it.

I haven't decided yet how to proceed. If I could order rod bearings for 20 bucks or so, it would probably be worth standing it on one end and pulling the pan, and putting in a new bearing. Then see if I can fix the pump, then see how it runs/sounds. Check for blowby/etc. to determine the condition of the engine overall.

But if it's hundreds of dollars, if I have to buy a whole rebuild kit, then I'm probably going to let it go and move on.

Oh well.

Bob
"Never be afraid to try something new. How hard can it be?"
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Re: New to me: Kubota D650 15HP

Post by thebuildist »

$53 for a set of standard rod bearings. I guess I have to at least pull the pan off and see what I find.

Bob
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Re: New to me: Kubota D650 15HP

Post by Harry »

Bob I feel your pain. I’ve been caught up in one of those before. It ran when I parked it deals. I’m sure you’ll get it sorted out and be ahead of the game. :peace: Harry
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Re: New to me: Kubota D650 15HP

Post by JSinMO »

Dang I was hoping you got a good one. But it still may be salvageable. If what you’re thinking is right I’d be interested to know if there is any indication the diesel shop had the pan off. Loose pan bolts, broken gaskets? If the crank journals look ok maybe it just needs bearing maybe the guy just didn’t want to pay for repairs.

I’ve got my fingers crossed on this one. Looking forward to what you find.
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Re: New to me: Kubota D650 15HP

Post by thebuildist »

This morning on my workbench I found an "extra" part left over from the pump rebuild. The round spacer that goes in between the cam follower and the "piston" shaft. Without that spacer the piston isn't moving enough to pump.

So that explains that.

Still have to pull the oil pan some time.

Bob
"Never be afraid to try something new. How hard can it be?"
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