BX1870 strange starting issue

[smokingcrater]

So my BX1870 (about 50 hours on the clock) developed a strange problem. It appears this only happens when it is cold, under 15F or so.

When I first start it, it starts but smokes like crazy and almost goes into a runaway condition. It revs way up regardless of throttle position, and sometimes I have to cycle the key off twice for it to shut down! (Trust me, having it rev itself WAY up and not having it shut down when the key is off is disconcerting to say the least!) Anyway, after it does this, it will not restart without sitting for a couple hours, at which point it starts and runs normally. Also, I recently discovered that it will SOMETIMES re-start if I run the throttle all the way up and then drop it back to idle while it is being cranked. If that works, you can hear a fairly subtle 'click' somewhere near full throttle.

So my complete non-diesel-mechanic brain tells me I have two issues. First is how is it getting fuel to go into runaway condition while the throttle is at idle. The second is the no-restart condition. The fuel shutoff valve could be responsible for the second problem, but not the first. Also, I am not 100% sure, but this problem MIGHT coincide with refueling with possibly unknown diesel. Again, once it is up and running, it blows snow fine, even in -20 weather.

 

[atitus74]

Are you treating your diesel fuel? If you have stock BX fuel filters they are kinda translucent when this happens can you see any ice in the filter ( meaning water in there.) If no ice you may have fuel gelling.

 

[JK22]

Check to make sure everything is in order on your throttle control cable (this picture is on the left side of engine bay if you are sitting on the seat). And take a video next time it happens to show your dealer. You are under warranty. Might as well take advantage of the warranty while you have it.

 

[smokingcrater]

Are you treating your diesel fuel? If you have stock BX fuel filters they are kinda translucent when this happens can you see any ice in the filter ( meaning water in there.) If no ice you may have fuel gelling.

Thought about that, but I would think that would affect more than starting. It blows snow like crazy once it starts, even if it is bone chilling cold (-20f was the coldest). I have not treated the fuel, and I really don't know what fuel was in the diesel can. (long story, but I unexpectedly inherited the tractor)

As much as I don't see how it could be fuel, I'm really tempted to eliminate that variable and go to known fresh diesel since the time does roughly line up.

 

[smokingcrater]

View attachment 595623 Check to make sure everything is in order on your throttle control cable (this picture is on the left side of engine bay if you are sitting on the seat). And take a video next time it happens to show your dealer. You are under warranty. Might as well take advantage of the warranty while you have it.

Checked that also, everything looks good. I had to slightly tighten the nut on the other end of the cable so it holds tension, but that was done quite a while ago and doesn't correspond to this.

Video is a great idea, I didn't want to be without the tractor while it is snowing every week but that is winding down now I can get it to the dealer. Tricky part is that it is temperature dependent.

 

[JK22]

Checked that also, everything looks good. I had to slightly tighten the nut on the other end of the cable so it holds tension, but that was done quite a while ago and doesn't correspond to this.

Video is a great idea, I didn't want to be without the tractor while it is snowing every week but that is winding down now I can get it to the dealer. Tricky part is that it is temperature dependent.

I suspect your problem might have something to do with the lever with the red screw right above the throttle cable assembly in my picture. That’s the only thing that “clicks” once the tractor is off. And I just tried starting my BX with that lever engaged and it won’t turn over. Hopefully someone will come along and educate us both on what that assembly does...

 

[smokingcrater]

I suspect your problem might have something to do with the lever with the red screw right above the throttle cable assembly in my picture. That’s the only thing that “clicks” once the tractor is off. And I just tried starting my BX with that lever engaged and it won’t turn over. Hopefully someone will come along and educate us both on what that assembly does...

So from what I've seen on the service manual, that is the fuel shutoff valve. When you turn the key off, that solenoid fires and closes, shutting down the fuel and the engine. (the click 10 seconds after shutdown is the solenoid letting go and letting the fuel valve open back up.) No matter what, that valve seems to be at the center of my problems.

 

[JK22]

So from what I've seen on the service manual, that is the fuel shutoff valve. When you turn the key off, that solenoid fires and closes, shutting down the fuel and the engine. (the click 10 seconds after shutdown is the solenoid letting go and letting the fuel valve open back up.) No matter what, that valve seems to be at the center of my problems.

Well at least we are getting somewhere! I’d pump out as much of that old fuel as you can, fill with new fuel and see if the problem disappears. Some good old #2 from the pump for new fuel. There is lots of debate over whether you should treat fuel in a BX. The manual says not to, so I don’t (at least not while I’m still under warranty). And grab a Mr. Funnel while your at it and only fill through that.

 

[Dave M7040]

So my BX1870 (about 50 hours on the clock) developed a strange problem. It appears this only happens when it is cold, under 15F or so.

When I first start it, it starts but smokes like crazy and almost goes into a runaway condition. It revs way up regardless of throttle position, and sometimes I have to cycle the key off twice for it to shut down! (Trust me, having it rev itself WAY up and not having it shut down when the key is off is disconcerting to say the least!) Anyway, after it does this, it will not restart without sitting for a couple hours, at which point it starts and runs normally. Also, I recently discovered that it will SOMETIMES re-start if I run the throttle all the way up and then drop it back to idle while it is being cranked. If that works, you can hear a fairly subtle 'click' somewhere near full throttle.

So my complete non-diesel-mechanic brain tells me I have two issues. First is how is it getting fuel to go into runaway condition while the throttle is at idle. The second is the no-restart condition. The fuel shutoff valve could be responsible for the second problem, but not the first. Also, I am not 100% sure, but this problem MIGHT coincide with refueling with possibly unknown diesel. Again, once it is up and running, it blows snow fine, even in -20 weather.

Diesel engine "run-a-way," can and does happen and usually ends in a thrown rod. Do not believe your engine is turbo charged. The engine can run on crankcase oil. Frozen crankcase vent system can force oil out of the oil pan and into the intake manifold and the engine takes off. On turbo engines, oil from the crankcase, because of frozen vent , is forced up turbo drain line. Engine runs away often to destruction.

If this happens and you have a CO2 fire extinguisher, point it at the air intake and the Co2 will choke off the engines air supply. Do not use a dry chemical extinguisher. If you are prepared, you can block the air intake with a board or similar. Don't use your hand as the suction is severe enough to cause physical damage

These pictures are of a recall to an L series which solved freezing crankcase vent systems. I provide them to get you to your dealer asap.

Kubota has been recalling many of their tractors in cold weather areas. Sometimes the repairs are quite extensive with electric heaters being used to prevent vent freezing. The heaters draw so much power a larger alternator is necessary.

Make it a dealer issue before you end up with a pile of scrap.

Diesel Engine Runaway Compilation - YouTube

Dave M7040

 

[smokingcrater]

Diesel engine "run-a-way," can and does happen and usually ends in a thrown rod.

So it isn't really a true runaway. It revs itself up, but will sometimes shut down with the key on the first time, sometimes I have to quickly cycle the key on/off, and it shuts off that time. So far, it is 100% for shutting down on the first or second try. But yeah, a true runaway ends in a large repair bill!


My gut feeling is that it isn't crankcase oil, but something like a stuck fuel injector dumping fuel. The more I'm typing on this thread, the more I'm thinking it is possibly moisture in the fuel. For some reason it isn't gelling, but causing havoc in an injectors, sometimes...