Green Tractor Talk banner

JD 950 low compression - Advise on what to do next?

1378 Views 8 Replies 5 Participants Last post by  Dennisfly
It started smoking right before she died down in the woods with a load of course. Was getting fuel to the injectors so I decided to check compression before splurging on new injectors. She's down...

200 / 280 / 320

Book says like 375 minimum. I can't believe she worked this long afterwards.

Paid 3500 for her like 8 years ago. Should I rebuild? Is there any direct swap yanmar 3t90j long blocks out there? Not interested in used. Or should I sell her for a parts tractor and move on?

Just having a huge debate in my head wondering which direction I should go... Head shaking...

Any advise would be appreciated on what would YOU do.
Thanks!
See less See more
  • Like
Reactions: 3
1 - 9 of 9 Posts
I’d do a valve adjustment and retest
  • Like
Reactions: 5
How many hours on the old girl?
  • Like
Reactions: 3
How many hours on the old girl?
Clock had stopped at just 640 when I got it. Was told original hours until I realized it wasn't moving. You know. Father had it, mostly idle hours, blah blah blah as I helped place the hook in my own lip to prepare to jerk it myself. That was also after I made a trip 2 states away and back home to buy a descent tractor that wasn't beat all to heck and selling for twice as much.

I discovered used tractors sell cheaper in Maryland where farms may be average 20 acres compared to NC where they probably average 100 acres or more.
See less See more
  • Like
Reactions: 4
I’d do a valve adjustment and retest
Sounds like a legit answer here. This is my very first diesel. All new to me.

Thank you sir!!!
See less See more
  • Like
Reactions: 5
I would second the valve adjustment, try that first.
  • Like
Reactions: 5
It will be Sunday or next week but I looked it up and will adjust valves and report back (0.006 in. for JD 950). All new to diesels but very familiar with everything gas. And besides the compression amount, this is sounding more like working on my air cooled VW.

I haven't touched the valves on this tractor since I got it. Might just be the ticket.

Still hope yet. Thanks again!
See less See more
  • Like
Reactions: 4
I haven't touched the valves on this tractor since I got it. Might just be the ticket.
Recommended at 600 hrs.
  • Like
Reactions: 3
I had an 855 that did the same thing. I took it apart and it looked good inside. Very little ridge. Cylinders measured good, round with almost no taper. Main and rod bearings were all good. The problem was the rings. The end gap was three or four times what it should have been. I honed the cylinders and installed new rings. I had a machine shop grind the valves and surface the head. I needed two new valves, an injector, and rings. When I was done I had about $1000 and my time in it. It ran great for the next seven years until I sold it.
See less See more
  • Like
Reactions: 5
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top