Kubota BX25 sputtering under load (not fuel filters?)

[Old Coot]

But that should effect it if it is warm or cold. I can go up the same hill when it is cold and doesn't miss a beat. It runs fine while cold. After about an hour of running it starts stumbling and doesn't stumble all the time only occasionally.
And it doesn't stall out completely.. Only acts like it is going to. Then puts out some black smoke and starts running fine.

 

[Jeff F.]

I had a similar issue with my B3200. Only did it when warm and on a hill with the right side higher than the left. It also only acted up when warm.

I changed the filter to no avail. I cleaned out the tank and found rust like material in the fuel tank.

I surmise fuel did flow but only slowly. By the time I had the tractor warmed up and under load, the sediment blocked the flow.

I have had no problems since I cleaned the tank.

 

[aczlan]

Already replaced the air cleaner also. Changed fuel filters, and they were not dirty,
but don't know why they would cause this only when warm. Also why wouldn't it do it backing up a hill as well as driving forward up the hill. Something in the tank sounds reasonable, but why only when warm. Also I forgot to mention is after sputtering it puts out black smoke for a second or two.

As has been said, if the lift pump is weak it will have to work harder when driving uphill than backing up a hill. A weak lift pump could also be pumping less fuel when it warms up than when it is cold.

The black smoke after it stops sputtering is interesting, black smoke is a sign that you have too much fuel and not enough air.
I suppose if the injection pump is not getting enough fuel and the governor is saying "I need more fuel", once the fuel pump catches up and the injection pump has enough fuel again, it may dump too much fuel for a couple of seconds until the engine has enough RPMs to satisfy the governor.

Can you hear the lift pump running if you turn the key on but don't start the tractor? On our BX2660 you can hear the lift pump rattling a little bit if you turn the key on but don't start the tractor.

Aaron Z

 

[Old Coot]

Yes I can hear the pump clicking as soon as the ignition is on. I was wondering if the pump gets warm and quits for a few seconds. The black smoke is what I don't understand. Maybe your right about the governor. I just thought if I was not getting enough fuel I sure wouldn't get black smoke.
There seems to be a lot of people having this trouble with
on the BX tractors. Most people say change filters and that fixes it. I would have agreed because mine ran good for an hour or so and then right back to the same thing. I mow about four acres and a lot of hills, some times it runs fine. Nest time up the hill it stumbles. But when it is cold it runs fine and may run fine for a couple of hours then start again.
I read somewhere where a guy took his to his dealer and they couldn't find the problem. I understand since it is so intermittent.
I don't like crawling around these things anymore. I'm almost 82 and getting under these is a pain. I used to like this stuff but now it is becoming a pain.

 

[aczlan]

Perhaps next time it stumbles, try shutting it right off, then turn the key back on and see if the pump runs and sounds the same?
If its not putting out black smoke when it stumbles, it is not getting fuel and the governor will be wide open to try and get it back up to speed.
If it then starts putting out black smoke, my guess would be that it has gotten fuel again and since the governor is still wide open it will dump as much fuel as it can into the engine which will cause black smoke.

Aaron Z

 

[Old Coot]

As soon as it cools off here in Ohio I'll try some of the suggestions.

Question: has anyone considered the chance this is caused by some of the new emission controls? My daughter and son in law bought a new motorhome a couple of years ago and it had a Navastar engine in it. Instead of using the liquid injection system like most used, Navastar went their own way. For a over a year, till they finally got it figured out, my daughter was breaking down and towed in to get fixed under warranty. I'm not sure what they finally changed but now it works great. And I know it was caused by the emission controls they were using. One of the things they were told to do was stop and let it cool down then drive till it said stop again.
Also I want to thank all the guys for their responses. I'm going to try to get this thing working right. If anyone finds the trouble I hope they will tell us all what it is.

 

[aczlan]

Coincidentally, our BX2660 started doing almost the same thing the week after I posted in this thread.
To test, I pulled the hose from the output side of the electric pump, put a longer hose on, stuck it into a fuel can, then turned the key to "on" and waited for fuel (and waited, and waited).
It took most of a minute to get fuel out of the end of the hose and then it just dribbled out (the pump was clicking the whole time).
I pulled the line before the fuel pump and it gushed out, so I knew that the pump was the problem.
I called the local dealer and they wanted over $150 for the pump which seemed high (especially since it was just a basic fuel pump), but looking online for OEM parts I found prices ranging from $95-170.
I went to our local Napa store and bought a model 610-1050 "Posi-Flow" pump (4-7 PSI 12 volt electronic fuel pump).
It bolted up using the same bolt holes and I just had to splice the wires to move over the plug to the new pump.
I went and tested it last night, the tractor ran well and seems to have more power than it had previously.

Aaron Z

 

[Old Coot]

Is it still running good?

Mine seems to run fine for a couple of hours then begins to sputter at times. I can mow my plus 4 acres and it runs fine till I try to go up a steep hill. I can let it set for a while and it will do the hill without a sputter.
Something strange I found yesterday. After mowing for a couple of hours it stumbled on a small hill and I took the fuel cap off and notice the fuel was clear up to the bottom of the filler, just as if I had just filled it After a minute or so it was down a couple of inches. My first thought was it has an air bubble in the bottom and it is sucking air. So I ran a piece of tubing down into the tank and hooked it to the cap. Didn't help.
I'm thinking of trying it and keep refilling the tank every hour or so. After that it's replace fuel pump. But why does it do it only after running for a while.
Nothing about it makes sense to me.

 

[ultrarunner]

A lot of the molded plastic tanks are "Saddle" tanks... they are meant to be filled and checked of dead flat ground.

A saddle tank could look full and be half empty if insufficient time to equalize both sides?

 

[aczlan]

A lot of the molded plastic tanks are "Saddle" tanks... they are meant to be filled and checked of dead flat ground.
A saddle tank could look full and be half empty if insufficient time to equalize both sides?

Our BX2660 has a saddle tank, IIRC, there is a 3/8" hose that runs across from one side to the other to equalize the fuel level

Is it still running good?

Yes, my father in law went out and spent a couple of hours mowing with it today. He was very happy with it when he came back in and said that it ran perfectly. My wife has also used it to mow the yard and she said that it behaved well.

Mine seems to run fine for a couple of hours then begins to sputter at times. I can mow my plus 4 acres and it runs fine till I try to go up a steep hill. I can let it set for a while and it will do the hill without a sputter.
Something strange I found yesterday. After mowing for a couple of hours it stumbled on a small hill and I took the fuel cap off and notice the fuel was clear up to the bottom of the filler, just as if I had just filled it After a minute or so it was down a couple of inches. My first thought was it has an air bubble in the bottom and it is sucking air. So I ran a piece of tubing down into the tank and hooked it to the cap. Didn't help.
I'm thinking of trying it and keep refilling the tank every hour or so. After that it's replace fuel pump. But why does it do it only after running for a while.
Nothing about it makes sense to me.

With ours, it ran ok(ish) cold, warm or hot with a full tank, but once it got down to the bottom half of the tank, it started having issues.

If you want to have an easy test, run it to less than half a tank, pop the hood and put a quart container down by the injection pump. Remove the line for fuel coming into the pump, put it into the container and turn the key to "on" position. Fuel should flood out into the container. If it does not (or if it just barely trickles out like mine did), its a bad pump, or plugged filters. If it just trickles out, pull the mower deck, then remove the input line to the fuel filter (over a pan). If fuel rushes out (as mine did), its probbaly the pump.

Aaron Z