Hi all, I'm working on a John Deere 850 compact tractor with the Yanmar 3T80-J engine for a customer at work. This started last summer after he was complaining for almost 2 years about it overheating. It had a bad head gasket and warped head that I fixed and after it ran fine for maybe 15 hours.
He brought it back complaining of no power and a solid stream of thick black smoke out of the exhaust. When I started it there was also kind of a whistling noise from the exhaust that reminded me of the turbo in my Cummins when it's cold. Started with the fuel filter and it was about half covered with some kind of nasty white slime and about a quarter full of water. Changed that and still the same. I pulled the injectors and tested them and they were questionable so I ordered 3 new ones from Hoye Tractor as it was less than having them rebuilt. Put them in and after it got all the buildup out of the manifold and muffler it ran fine and no "whistle". He took it home and all was good until he had about 15 more hours on it and it did it again, only this time it would barely run up to 1000 rpm and the smoke was even worse.
He managed to drive it to me and when I went to check it over the whistle was back and louder. Checked the injectors and they popped and sprayed the way they should. Checked the filter and there was some water and dirt in it this time. Did a little checking on various sites and didn't really find anything about similar issues. Ended up pulling the pump and sending out to have it looked over and fixed. Finally got it back after a total rebuild cause it was completely wrecked internally, put it in along with flushing the tank, a new fuel filter, rubber lines, and fresh fuel and it fired right up and ran great. Drove it outside to let it warm up so I could road test it and let it run at half throttle. After about 20 minutes I went back to speed it up and take it for a drive and it ran fine until I tried to come up a hill then it was back smoke, no power, and it started knocking bad. Slowed it down and the smoke went away some but the whistle was back.
Brought it in and checked it over but couldn't really see anything that would cause it. I called the shop that rebuilt the pump and got a few suggestions from them and called one of my friends that used to work ata JD dealer and he asked around and got a few more suggestions. Tried everything but it didn't make any difference. Finally pulled the pump and sent it and all the injectors both old and new back to the rebuild shop. The original injectors were junk and the new ones opened a little under pressure. They set everything up they way it should be and said they were working together perfectly and suggested I check the governor to make sure it wasn't over-fueling the engine . I put them all back in and went step by step with the governor according to my I&T manual and it fired right up and ran fine other than I couldn't get it to speed up above 2000 rpm for the time it took me to drive it out of the shop and around the building.
Parked it to let it warm up and was moving the throttle to get to about 1750 on the tach and it did it again. I've since brought it back in and it appears the link between the governor and the rack on the pump slipped adjustment. Reset it and no change other than the smoke looked like it was a combination of black and white instead of solid black. As a last ditch attempt to fix it I loosened the adjustment on the same link and moved it the other way as it was a little confusing in the book when it said to move it all the way back, so I took a chance that they meant to the off position on the pump which goes forward on the engine as opposed to the back of the engine. Started it up and it cleaned right up and ran nice until i took it for a test drive and it started all over again. Just not as bad as before.
Figured I'd ask on here before I spend anymore time on it as I'm at my wits end trying to fix it.
Thanks in advance, Stewart