Senior MTF Member
Join Date: Oct 2009
Location: Central Michigan
Re: John Deere 670 Yanmar Engine problems
We used to have a 1960 Ford 851 diesel on the farm, and it developed the symptoms you're describing. It turned out that the fuel was leaking into the crankcase through the injector pump, and the pump had to be rebuilt ($$$).
Prior to the rebuild, we installed a fuel shut-off valve, and that slowed the problem substantially, but the fuel still leaked by when the engine was running.
Good luck with your problem, and when you get it fixed, give us an update?
2008 JD 2305
47" FM Snowblower
60" RM Frontier Blade
Home-built Ballast Box (400 lbs.)