L3800 Over Revs While Operating

[Bear9350]

While bush hogging yesterday (about 5 hours of run time) I had the engine RPMS spike 2x. Both times this happened maybe 30 minutes into operation. I was mowing pretty tall grass and brush down, working it decently. Both times this would happen, it would seem as if the tractor was loosing power for a minute or so before the engine rpms spiked. When the RPMs did spike it spewed mostly white smoke, and pegged the tack beyond 3,000 rpm. After shutting the engine down, I could start it back up right away and it seemed to run normal.

I bought this tractor used with about 1,000 hours on it last fall. Changed all the fluids and filters last November. Used it lightly for snowblowing (rear mounted) several times last fall where it did this same thing once. I was trailering the tractor yesterday and filled a nearly empty tank with off-road diesel from a popular station.

 

[#40Fan]

Start with the basic stuff.

Is the hydraulic fluid full? Did you use Kubota fluid or something else?

 

[Bear9350]

Start with the basic stuff.

Is the hydraulic fluid full? Did you use Kubota fluid or something else?

Hydraulic fluid level is good. After doing some reading I did use the recommended Kubota Hydralic oil.

 

[#40Fan]

After rereading your post, my initial thought and reason for asking about the fluid, went down the drain.

The white smoke would be from unburnt fuel or possibly coolant. If you had an injector sticking open and dumping fuel, that would create the misfire and smoke. The governor in the pump trying to compensate for the lack of power by giving it more throttle and when it finally stops misfiring, overshoots.

Might try some injector cleaner. Check the coolant level as well.

 

[WoodKutter]

I'm not trying to be a jerk, just trying to rule things out. Is it possible brush or debris hit the hand throttle or foot throttle, maybe the linkage?

 

[#40Fan]

Something else came to mind. Does this tractor have a DPF?

 

[Bear9350]

No worries. The first time this happened was last winter blowing snow in the middle of my driveway, no chance something got to the throttle there. Maybe could have one time yesterday, but not the other.

Also, the engine is reving far faster then it does at wot.

I'm not trying to be a jerk, just trying to rule things out. Is it possible brush or debris hit the hand throttle or foot throttle, maybe the linkage?

 

[Bear9350]

Nope, this one is pre-emissions.

Something else came to mind. Does this tractor have a DPF?

 

[Bear9350]

Yeah, that's about all I could figure was some sort of stuck injector or something. I will pick up some type of injector cleaner to dump in and see what happens.

After rereading your post, my initial thought and reason for asking about the fluid, went down the drain.

The white smoke would be from unburnt fuel or possibly coolant. If you had an injector sticking open and dumping fuel, that would create the misfire and smoke. The governor in the pump trying to compensate for the lack of power by giving it more throttle and when it finally stops misfiring, overshoots.

Might try some injector cleaner. Check the coolant level as well.

 

[Russell King]

Sounds like the engine is getting fuel from an uncontrolled source. Check engine oil level, check inside the air filter housing and where any crank case ventilation pipes enter the air intake and see if the area is oily.

Read about run away Diesel engines and see if that is similar to what is happening on your engine, learn how to get your engine shut down quickly if you think it is in run away condition.

Could the hydraulic pump be leaking hydraulic fluid into the engine and over filling the crank case?

 

[MOOTS]

After rereading your post, my initial thought and reason for asking about the fluid, went down the drain.

The white smoke would be from unburnt fuel or possibly coolant. If you had an injector sticking open and dumping fuel, that would create the misfire and smoke. The governor in the pump trying to compensate for the lack of power by giving it more throttle and when it finally stops misfiring, overshoots.

Might try some injector cleaner. Check the coolant level as well.

Black smoke is unburnt fuel(rolling coal for all the millennials)
White is coolant.
Blue is oil.

 

[#40Fan]

Black smoke is unburnt fuel(rolling coal for all the millennials)
White is coolant.
Blue is oil.

Black is an overabundance of fuel.

 

[MOOTS]

Black is an overabundance of fuel.

Correct, and it’s unburnt.

 

[woodman55]

Sounds like governor issues. I would pull the pump and have it checked/tested by an injection shop. Compared to over revving your engine and throwing a rod, having the pump done is cheap.

 

[Bear9350]

It does take off like a run-way, but I can either turn the key off and it shuts down like normal, or after a few seconds of running, seems to burn all the excess fuel up and return to normal.

I put a couple more hours on it Saturday with no issue. For now I plan to run some injector cleaner through it and continue to monitor the fluids etc..