# JD 750 w/ Yanmar 3T80U-J



## crkranz (3 mo ago)

Bought a used 750 from a lady that had been sitting outside for a few years and is in pretty rough shape. Hour meter was replaced so dont know real hrs. Was her husbands and she doenst really know anything about it and doesnt think it has run in approx. 4 years. But supposedly did run when parked but son couldnt get it started a couple years ago. Anyhow it is my problem now. 

I've done all the fluids, cleaned the fuel tank and replaced all the lines and filter. I replaced water pump/starter/battery and went through entire wiring harness and fixed some issues. The old fluids didnt look to bad and didnt notice any water in the oil. 

Bled the fuel lines per manual and noticed I was not getting any fuel past the injector pump. Nothing coming out at the of top of injector pump. Removed the fuel injection pump and plungers weren't stuck and rack moves back and forth without too much effort. 

Any ideas on where I should go from here? New inj. pump? 

I'll try and post some video tonight.


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## crkranz (3 mo ago)

John Deere 750 - Injector Pump not pumping
Video of injector pump with lines disconnected


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## bmaverick (Feb 20, 2014)

crkranz said:


> Bought a used 750 from a lady that had been sitting outside for a few years and is in pretty rough shape. Hour meter was replaced so dont know real hrs. Was her husbands and she doenst really know anything about it and doesnt think it has run in approx. 4 years. But supposedly did run when parked but son couldnt get it started a couple years ago. Anyhow it is my problem now.
> 
> I've done all the fluids, cleaned the fuel tank and replaced all the lines and filter. I replaced water pump/starter/battery and went through entire wiring harness and fixed some issues. The old fluids didnt look to bad and didnt notice any water in the oil.
> 
> ...


Oh, I wish I had seen your posting earlier before taking the pump off. 

Your JD750 is really a Yanmar in JD green paint. It's a Yanmar F or FX series chassis frame with the Yanmar 3T80 engine family from the YM2500, YM2610, JD850 and a few others. I have the YM2610 version of your machine. 

Over at the Yanmar Tractor Owners Group, we have the service manuals for free. Even the one about the fuel injector pump and how to bleed the injectors to the cylinders to make it all work. The link is below in my signature.


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## crkranz (3 mo ago)

bmaverick said:


> Oh, I wish I had seen your posting earlier before taking the pump off.
> 
> Your JD750 is really a Yanmar in JD green paint. It's a Yanmar F or FX series chassis frame with the Yanmar 3T80 engine family from the YM2500, YM2610, JD850 and a few others. I have the YM2610 version of your machine.
> 
> Over at the Yanmar Tractor Owners Group, we have the service manuals for free. Even the one about the fuel injector pump and how to bleed the injectors to the cylinders to make it all work. The link is below in my signature.


Thx. I do have the 750 service manual. All it says is to replace injector pump if faulty. Trying to determine if it is indeed faulty or not or if it is something else.


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## Tx Jim (Jul 28, 2020)

Do you have a good fuel supply to inj pump? Do you have fuel cutoff engaged so fuel can flow through it. If it was my tractor I attach lines & put trans in higher gear & attempt to tow start it. 

I once owned a Ford 3000 diesel that fuel gauge was inoperable. When engine was operated until there was no diesel in the tank it was a ""bear to bleed fuel system"" & get engine running. I'd normally tow the 3000 about 10-15 ft & it would fire up.


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## crkranz (3 mo ago)

Tx Jim said:


> Do you have a good fuel supply to inj pump? Do you have fuel cutoff engaged so fuel can flow through it. If it was my tractor I attach lines & put trans in higher gear & attempt to tow start it.
> 
> I once owned a Ford 3000 diesel that fuel gauge was inoperable. When engine was operated until there was no diesel in the tank it was a ""bear to bleed fuel system"" & get engine running. I'd normally tow the 3000 about 10-15 ft & it would fire up.


Yep replaced all the lines/filters to the pump and have good flow to pump.


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## Tx Jim (Jul 28, 2020)

Do you have a tow chain or strap & a tow vehicle with a driver??


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## crkranz (3 mo ago)

Tx Jim said:


> Do you have a tow chain or strap & a tow vehicle with a driver??


Currently parked in my garage in town, not sure if I want to tow it down the city street just yet 
Also a bit apprehensive as I've never had it running and dont know what else could be wrong. 
I might try it if I cant figure anything else out.


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## Tx Jim (Jul 28, 2020)

I'd fill fuel filter with auto trans fluid then proceed to get tranny fluid bleed to inj pump in hopes of lubing inj pump plungers. Back 40+ yrs ago when I changed fuel filters on an 18 wheeler truck engine I always filled fuel filter with tranny oil & it always started with no problems


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## bmaverick (Feb 20, 2014)

crkranz said:


> Thx. I do have the 750 service manual. All it says is to replace injector pump if faulty. Trying to determine if it is indeed faulty or not or if it is something else.


The injector pumps can be rebuilt. Either you can 'try' it or the best person on many of these forums for the rebuilds is ThepumpguySC. He's a Master fuel and hydraulic pump rebuilder.


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## crkranz (3 mo ago)

bmaverick said:


> The injector pumps can be rebuilt. Either you can 'try' it or the best person on many of these forums for the rebuilds is ThepumpguySC. He's a Master fuel and hydraulic pump rebuilder.


I reached out to him and ended up ordering a new pump. We'll see what happens when it gets here.


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## thepumpguysc (Jan 25, 2015)

Unfortunately the parts for his pump are quite expensive.. by his description he’s gonna need plunger and barrels..
Those babies cost over 100.00 each..
add that to all the gaskets and orings + a little labor and your over the Hoye price..
It only makes sense to order one from Hoye..


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## crkranz (3 mo ago)

PJSC was very generous with his time answering my newbie questions. It is much appreciated. Hopefully the pump shows up by this weekend. Got shoulder surgery coming up and will be be out of commission for a few months. This wasn’t supposed to be taking this long. Waiting for parts is a killer.


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## jrelkhunt (8 mo ago)

crkranz said:


> Bought a used 750 from a lady that had been sitting outside for a few years and is in pretty rough shape. Hour meter was replaced so dont know real hrs. Was her husbands and she doenst really know anything about it and doesnt think it has run in approx. 4 years. But supposedly did run when parked but son couldnt get it started a couple years ago. Anyhow it is my problem now.
> 
> I've done all the fluids, cleaned the fuel tank and replaced all the lines and filter. I replaced water pump/starter/battery and went through entire wiring harness and fixed some issues. The old fluids didnt look to bad and didnt notice any water in the oil.
> 
> ...


SHE SHOULDNT HAVE SAT OUTSIDE FOR A FEW YEARS--SHE SHOULD HAVE BEEN INSIDE THE GARAGE TAKING CARE OF HER TRACTOR..


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## crkranz (3 mo ago)

jrelkhunt said:


> SHE SHOULDNT HAVE SAT OUTSIDE FOR A FEW YEARS--SHE SHOULD HAVE BEEN INSIDE THE GARAGE TAKING CARE OF HER TRACTOR..


Yeah hard to believe people dont take care of their stuff - but if it was nice I would have had to pay a lot more for it. Got it at a price that I can afford to fix whatever. Was hoping to get lucky and not have anything major wrong, but not off to good start. Got compression tester coming in mail today and will be interested to see what that says. Hoping Hoye gets off their butts and ships my pump today. Time is ticking.


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## thepumpguysc (Jan 25, 2015)

R your injectors the type that the line goes INTO the injector and has male threads on the line.??
If so, where r u going to find a compression adapter to fit in the hole.?
And a line to go to the gauge.??
If u had an extra injector, u could gut it and braze up the inlet and run a fitting out of the return hole on top of the inj. to go to your gauge..


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## crkranz (3 mo ago)

thepumpguysc said:


> R your injectors the type that the line goes INTO the injector and has male threads on the line.??
> If so, where r u going to find a compression adapter to fit in the hole.?
> And a line to go to the gauge.??
> If u had an extra injector, u could gut it and braze up the inlet and run a fitting out of the return hole on top of the inj. to go to your gauge..


Hoye sells an adapter for this engine. $22


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## thepumpguysc (Jan 25, 2015)

Well I’ll be.. nice find..


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## thepumpguysc (Jan 25, 2015)

Don’t forget to get new fiber washers for the bottom of the injectors..


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## crkranz (3 mo ago)

thepumpguysc said:


> Don’t forget to get new fiber washers for the bottom of the injectors..


Will do. Thx! Compression tester adapter supposed to show up today. Hoping to have time tonight to test. 

On youtube I've seen people loosen the nuts a ways on the fuel injector retainer clamp then spin engine over to get the injectors to pop out for easy removal. Think this is how I'm going to try and get injectors out if they are stuck in there.


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## thepumpguysc (Jan 25, 2015)

Good luck with that..
I ended up buying the injector removal tool from Hoye.. lol
I know every trick in the book and have either tried it or watched it being done..
And still ended up buying the tool.!!! Lol


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## crkranz (3 mo ago)

Got to work on it a bit last night. The injectors popped right out after using the engine compression to loosen them up. Did 3 sets of tests and bad news is 300-250-100 psi compression. Probably going to figure out how to do leak down test or maybe just pull the head off and see what cylinders look like.


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## bmaverick (Feb 20, 2014)

crkranz said:


> Got to work on it a bit last night. The injectors popped right out after using the engine compression to loosen them up. Did 3 sets of tests and bad news is 300-250-100 psi compression. Probably going to figure out how to do leak down test or maybe just pull the head off and see what cylinders look like.


There are a few rebuild kits out there for the 3T80 engine. Shop around and see what every kit includes.


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## crkranz (3 mo ago)

bmaverick said:


> There are a few rebuild kits out there for the 3T80 engine. Shop around and see what every kit includes.


Yep. I have watched a couple yanmar rebuilds on youtube. In-frame and complete overhaul. Hoping cylinders arent too bad and can do in-frame - I'm due for a bit of luck. Will probably pull head this weekend and see what it looks like.


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## crkranz (3 mo ago)

Pulled head off this weekend and more bad news. Piston rings were broken in 2 of 3 cylinders. Guessing they used starting fluid to try and get it started at one point. Pistons have some scoring and one has a crack in the skirt.

Cylinder walls dont look too bad upon initial inspection. Top of the middle cylinder is the worst as that was probably the one with exhaust valve open whole time while sitting there. Some corrosion top - but seems to be above top piston ring. Going to lightly run a hone through cylinders and see what shows up.

Also pulled all the valves out of the head and other than the 1 open exhaust port the rest looked ok. Valve guides seem fine. Will probably lap valves and see what profile looks likes and go from there. Head is pretty flat and head gasket didnt appear that it was leaking.

This is my first diesel and dont have a lot of engine experience - so this project has been quite the learning experience. Thank goodness for the manual, forums like this and almighty youtube.


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## bmaverick (Feb 20, 2014)

crkranz said:


> Pulled head off this weekend and more bad news. Piston rings were broken in 2 of 3 cylinders. Guessing they used starting fluid to try and get it started at one point. Pistons have some scoring and one has a crack in the skirt.
> 
> Cylinder walls dont look too bad upon initial inspection. Top of the middle cylinder is the worst as that was probably the one with exhaust valve open whole time while sitting there. Some corrosion top - but seems to be above top piston ring. Going to lightly run a hone through cylinders and see what shows up.
> 
> ...


Thanks for the feedback. 

Yes, if honing the cylinder sleeves helps, you don't need to be involved in replacing them. 

I would 'advise' knowing the rings became damaged that you then pull the pan and check the crank bearings. Running too long with slapping pistons up and down can put a bunch of strain on those lower engine bearings on the crankshaft that sits fairly level and straight. 

About the head, do you have a spring effort gauge to see if the springs there are all a bit consistent with one another? Since the head is off, now is the time to verify. 
*Tension and Compression Force Gauges*








McMaster-Carr


McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.




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The old school way. And I mean just that, I had used these back in 5th grade when real learning was the best!








McMaster-Carr


McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.




www.mcmaster.com


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## crkranz (3 mo ago)

No cyl. sleeves in this engine. I have to get new pistons/rings so I will run a hone though the cylinder to clean them up a little then inspect and measure them and see where I'm at. Hoping to not have to pull engine completely and can do an inframe rebuild, which is a lot easier/cheaper then having to pull engine and do complete overhaul. 

Manual has a spring height tolerance and I will check that.


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## bmaverick (Feb 20, 2014)

crkranz said:


> No cyl. sleeves in this engine. I have to get new pistons/rings so I will run a hone though the cylinder to clean them up a little then inspect and measure them and see where I'm at. Hoping to not have to pull engine completely and can do an inframe rebuild, which is a lot easier/cheaper then having to pull engine and do complete overhaul.
> 
> Manual has a spring height tolerance, and I will check that.


Yanmar made two iterations of the 3T80, with sleeves and without sleeves. Most, not all in the Yanmar lineup has sleeves. I believe at least 2 do not. The sleeved engines are the way to go for longevity. The JD850 3T80 has sleeves. The JD750 was made in production years later. It may have been a cost savings measure.


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## crkranz (3 mo ago)

I am a bit concerned about keeping crank clean and protecting its bearings from contamination when doing in-frame overhaul. How to keep clean and how to clean before final re-assembly?


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## bmaverick (Feb 20, 2014)

crkranz said:


> I am a bit concerned about keeping crank clean and protecting its bearings from contamination when doing in-frame overhaul. How to keep clean and how to clean before final re-assembly?


All of the honing I've seen also had the bottom end cleared too. Either way, to keep all clean, remove the bottom pan, crankshaft, crank rods, pistons, rings, bearings. 

DO MARK the position of the crankshaft and other concerned parts before dis-assembly. The engine is mechanically timed. Also look for marking on the crankshaft and those other parts of interest too. Take plenty of pixs as you work, not just as a log of the work, but info you may need later.


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## crkranz (3 mo ago)

Honed the cylinders and they seemed to clean up pretty well. Measured the cylinders with a bore gauge and seemed within spec. Cleaned the seats and valves then lapped them. They dont look too bad either, even the one bad exhaust port looks passable.

Just put my order in for top end gasket kit, pistons and rings. Hoping to put it all together this next weekend.


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## crkranz (3 mo ago)

Another setback in getting this tractor up and running. Reassembling engine and was installing injectors and broke one of the retainer brackets because I misread the manual and overtightened them. Of course this part is non-existant and may have to fabricate replacements - which shouldnt be too hard.


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## thepumpguysc (Jan 25, 2015)

70 FTLBS.?? THAT seems a bit excessive to me..
Personally I’ve never torqued 1..
I just tightened them up EVENLY..
Evenly seems to be the key..
Sorry for your troubles..


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## crkranz (3 mo ago)

thepumpguysc said:


> 70 FTLBS.?? THAT seems a bit excessive to me..
> Personally I’ve never torqued 1..
> I just tightened them up EVENLY..
> Evenly seems to be the key..
> Sorry for your troubles..


Yeah, I misread the manual and way over torqued. Should only be around 20. There are 2 parts similarly referred to as nozzle retainer nuts. Live and learn.


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## bmaverick (Feb 20, 2014)

crkranz said:


> Another setback in getting this tractor up and running. Reassembling engine and was installing injectors and broke one of the retainer brackets and another looks like it may have a crack . Service manual calls for 70ft-lbs of torque. Wondering why this happened and if spec is correct. Would be interesting to find the yanmar manual and compare to my JD manual. Of course this part is non-existant and may have to fabricate replacements - which shouldnt be too hard. Need to figure out why this happened though.
> 
> View attachment 82954


One thing us Yanmar owners have learned with any of the Yanmar Service Manuals dealing with torqued fasteners, NEVER TRUST what's in the manual. We've seen so many broke parts due to wrong values in these manuals.


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## bmaverick (Feb 20, 2014)

crkranz said:


> Yeah, I misread the manual and way over torqued. Should only be around 20. There are 2 parts similarly referred to as nozzle retainer nuts. Live and learn.


Reach out to Fredricks Equipment in AL. They have the parts in stock.


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## crkranz (3 mo ago)

bmaverick said:


> Reach out to Fredricks Equipment in AL. They have the parts in stock.


Thanks will do. Do you know what yanmar model closest matches my 750? I think you said there are service and parts manuals available free somewhere? Might be a nice backup reference.


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## bmaverick (Feb 20, 2014)

crkranz said:


> Thanks will do. Do you know what yanmar model closest matches my 750? I think you said there are service and parts manuals available free somewhere? Might be a nice backup reference.


Follow the link below in my signature.  

The JD750 uses the same base 3T80 engine as the JD850. However, we did note the JD750 has no engine sleeves, thus its a U-J vs just the J. The Yanmar YM1820 has the 3T80U-NB and the YM2002 has the 3T80U-NA, YMG2000 has the 3T80U-SA. 

Some of the F & FX Series use the engine too. The JD750 came out much later than the original 50 Series machines. The JD750 has the F & FX Series rear renders while keeping the original front hood of the JD850/JD950. 
The ROPS reflects the US made Yanmars of the YM276 and higher.


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## crkranz (3 mo ago)

Picked up my new 'custom' injector retainers. They turned out pretty nice. Had a friend cut them from 1/2" plate. Fredricks thought they had some used ones at a decent price but the guy never got back to me and I didnt want to wait around on shipping.

Next snag - the chamber gaskets I ordered from Hoye were not correct so I reordered them thinking I ordered wrong ones - nope still not right. Not sure what is going on with this part # but I found some OEM ones on Ebay.

Got new injector pump installed and shimmed to right timing. So entire fuel system is basically new. A couple more items to button up and then time to see if it will run. Hopefully tonight.


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## crkranz (3 mo ago)

bmaverick said:


> The JD750 has the F & FX Series rear renders while keeping the original front hood of the JD850/JD950.


So you think the 6/7/8/950 hoods are interchangable? If so I might keep my eye out for a better one. Mine is pretty rough.


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## bmaverick (Feb 20, 2014)

crkranz said:


> So you think the 6/7/8/950 hoods are interchangable? If so I might keep my eye out for a better one. Mine is pretty rough.


The JD650 hood is way different. I wouldn't trust it as it's on a 2-cylinder setup machine.

JD650 is an SCUT and not a CUT machine. It 'could' crossover to SCUT Yanmars of similar size, ie. YM186 or YM187 or YM195.


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## crkranz (3 mo ago)

Last night finally got everything back together, bled the fuel lines and it fired right up. I think my wife was beginning to doubt it would ever run.

750 start up

Pretty happy right now - other than a small oil pan leak. I used rtv instead of a gasket and there is no clearance between the block/oil pickup/drive shaft. Will probably redo when time for oil change.


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## crkranz (3 mo ago)

So far....
went through entire wiring harness
replaced fuel lines, pump and injectors
replaced starter and water pump and hoses
honed block and replaced pistons/rings/rod bearings
new head gasket 
lapped and adjusted valves
changed all fluids

Never have worked on diesel before and the good thing is I now feel I know this tractor pretty darn well. 
It is actually a pretty simple and easy engine to work on and parts availability has been good. 

None of the lights work so still need to figure that out then will be working on loader, snowblower and belly/finish mowers that came with it.


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## jd110 (Nov 23, 2015)

Congrats on getting her running. Sounds good. Did you get a chance to try the clutch? Since it has been sitting so long I am wondering if clutch may be stuck. 750 is a sweet little tractor.


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## bmaverick (Feb 20, 2014)

crkranz said:


> Last night finally got everything back together, bled the fuel lines and it fired right up. I think my wife was beginning to doubt it would ever run.
> 
> 750 start up
> 
> Pretty happy right now - other than a small oil pan leak. I used rtv instead of a gasket and there is no clearance between the block/oil pickup/drive shaft. Will probably redo when time for oil change.


The engine purrs just like any other Yanmar 3T80 engine. Very nice!


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## bmaverick (Feb 20, 2014)

crkranz said:


> None of the lights work so still need to figure that out then will be working on loader, snowblower and belly/finish mowers that came with it.


Do the headlamps show Stanley 001-1259 or other Stanley number? If so, the Wagner HM202 bulbs are the ones you really need. The old school P15D-25 are hard to find and pricey. The HM202's are easy to get, even from RockAuto.com for a mere $1.83 each. 

The Deere p/n for the headlamp assy is HL5414. End connector could vary for 3 types.









The 40 year old style bulbs Yanmar used are these. P15D-25. The 25mm is the diameter of the base ring.









I took and measured the headlamp assemblies.



























After all that, I found the match up looking thru Honda and Kawasaki ATV and UTV forums on what they are using today.

The H6M (HM202) halogens are plug-n-play. No mods to anything. Perfect fit. AND it's low and high beam too!










If my machine was JD green, it would look like a JD950 with the JD850 engine 3T80.
Those halogens as way brighter than the original P15D-25 bulbs.










BTW, I bet you need a working rear work light. Harbor Freight has them for $9 with coupon at times. It looks so much like the OE Yanmar used. And it mounts in the SAME fender hole.


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## crkranz (3 mo ago)

Thanks for info on lights - still havent looked into that issue. The bulbs look ok, but no lights work so I think it is a wiring issue.

I was a bit worried about the clutch and brakes but it seems to be fine. I have only driven it around the block a few times so havent tested it very hard.

Also, filled the thermostart reservoir up with diesel and verified that system is functional.

Got the loader back on and all the hydraulics work so far (power steering/rockshaft/loader) which is a relief. I need to figure out a stand or something to make taking loader on/off easier. If anybody has a good system - I would love to see it.


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## bmaverick (Feb 20, 2014)

crkranz said:


> Thanks for info on lights - still havent looked into that issue. The bulbs look ok, but no lights work so I think it is a wiring issue.
> 
> I was a bit worried about the clutch and brakes but it seems to be fine. I have only driven it around the block a few times so havent tested it very hard.
> 
> ...


Before getting into any wire-harness, please check the fuses first.  

The power steering needs to be inspected for weeps or leaks often. The Yanmar OE units are prone to this. If your machine has an aftermarket version, then no big deal. So, if it's painted green, it' the Yanmar PS system.


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## crkranz (3 mo ago)

bmaverick said:


> Before getting into any wire-harness, please check the fuses first.
> 
> The power steering needs to be inspected for weeps or leaks often. The Yanmar OE units are prone to this. If your machine has an aftermarket version, then no big deal. So, if it's painted green, it' the Yanmar PS system.


I have power at the fuse block and checked all fuses. 
Went thought entire wiring harness - except lighting circuits - yet. Everything under the dash/cowl is now in good shape. Maybe bad switch/plug/bulbs - I will do a bit of testing with the multimeter when I get time and see where problem is. 
Getting machine operational was main goal - now can work on the little stuff like this.

I would assume the PS unit is OE and dont see any leaks, but will look it over. Just glad I have it. I did already replace 2 PS hoses as they were badly weathered (but not leaking).


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## roadpacker (Jul 7, 2015)

crkranz said:


> I have power at the fuse block and checked all fuses.
> Went thought entire wiring harness - except lighting circuits - yet. Everything under the dash/cowl is now in good shape. Maybe bad switch/plug/bulbs - I will do a bit of testing with the multimeter when I get time and see where problem is.
> Getting machine operational was main goal - now can work on the little stuff like this.
> 
> I would assume the PS unit is OE and dont see any leaks, but will look it over. Just glad I have it. I did already replace 2 PS hoses as they were badly weathered (but not leaking).


On my JD 950, I also had light issues and had power to the up stream side of each fuse in the fuse block, fuses were good,but no power out of the fuse block,Took the block off and removed each fuse holder and scrubbed the holder up clean with fine grit sand paper. Turned out, the individual fuse holders were oxidized enough to prevent flow out of the holder. Couldn't see the oxidation, but a ohm meter will quickly find it.


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## crkranz (3 mo ago)

thx, I will check. Might not happen till spring as tractor is going into storage soon.


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## roadpacker (Jul 7, 2015)

Copy spring,winter is here! Having a freeze tonight- too cold for Alabama in mid November.


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