John Deere 850 Started Running Rough and Blowing Acrid White Smoke

[Matt Hightower]

Hi all,

I have a 1985 John Deere 850 (3-cyl Yanmar diesel) with just over 1,000 hours. Today I was running the Bush Hog and everything was fine for over two hours of runtime (a little bit of smoke from the blow-by tube after awhile, but it was a HOT day.) All of a sudden in the middle of a pass it started running noticeably rougher and blowing white smoke. Not bellows, but it normally does not smoke at all. Now even after cool down it starts and runs quite rough and blows white smoke. If I idle down below 1k RPMs it dies. The smoke smells acidic (unburnt fuel) not sweet (coolant).

It has not leaked a drop of any fluid before. Now I have (literally) two drops of fuel on the shop floor and the middle injector is wet around the nut. The other two injectors are dry. The top of the gas tank is also wet, apparently from the return line.

I have limited experience with diesels, so would GREATLY appreciate any direction you guys can give as to what may have happened and how I can diagnose and fix the problem.

Thank you in advance!

Hightower

 

[jd110]

It sounds like you have misfire from maybe a bad fuel injector or possibly low compression. While the engine is running, loosen each line at the injectors one at a time. If the engine worsens when an injector is loosened, then that cylinder is firing. If you find one cylinder that makes no difference when the line is loosened, then that is the cylinder that is misfiring. SOmetimes the smoke will go away when the bad injector is loosened. Remove the bad injector and take it to your dealer or a diesel shop to be tested. A diesel shop can probably rebuild it for you.

 

[Tx Jim]

If you choose to loosen inj. lines be sure and keep your fingers away from any spraying diesel. The high pressure diesel can be injected under the skin which will be very ""BAD"". How long since fuel filter was changed????

 

[spruce Deere]

I would do what jd110 suggested, It sounds like a injector issue to me.

Did the blow-by get worse to when it started running rough??

If ya do end up pulling and injector, might as well do all three.... get them all checked out

 

[Matt Hightower]

Ok, so now I'm really confused.

I went down earlier to check the coolant level, the oil, etc.; all checked out fine. Nothing had leaked while the tractor's been off.

I fired it up and noted the same condition; rough running with occasional knock and white smoke with mild diesel smell from the exhaust. When I would idle down to 1k, it would erratically rev up and down. If I idled down further it would die.

After a few minutes though it started to clear up. It would smooth out a little then get rough again. Then got smoother. Still producing white smoke though.

I decided to put it in gear and see what it did under a load. At this point it was noticeably smoother, although still sending up white smoke.

After a few passes under load though, it seems back to normal; minimal if any smoking, smooth(er) idle, smooth throttle up and down, will idle all the way down to 750 rpm. It's still sending some smoke out the blow-by tube, but I can't honestly say if it's more than before or not.

What has me concerned now is, a) what was the problem, and b) why did it clear up in 30 minutes of runtime? I top off the tank every time I shut down, but other than that no fuel, oil, or coolant changes.

If it continues to operate "normally", is it safe to do so? I don't want to risk damage to the tractor.

Thanks for all of your input!

Hightower

 

[ccsial]

Almost souds like some crud got into the fuel system. I'd replace the fuel filter at least.

 

[megaboz]

Probably wouldn't hurt to double dose it with some high quality fuel treatment. Might be some injector build up.

 

[kuboman]

Sounds like water in the fuel or even something else, gas etc. I would flush the tank, change the fuel filter and give a heavy dose of fuel conditioner. If it never completely cleans up then I would pull the injectors and have them serviced.

 

[charleyfarmall]

Sounds like water in the fuel or even something else, gas etc. I would flush the tank, change the fuel filter and give a heavy dose of fuel conditioner. If it never completely cleans up then I would pull the injectors and have them serviced.

This is where I would start...