Kubota BX25 sputtering under load (not fuel filters?)

   / Kubota BX25 sputtering under load (not fuel filters?) #51  
I know the OP was a while ago, but just had this issue with my 2012 BX25. I changed front and rear fuel filters, bled the system, and had stalls and no power after it warmed up. I pulled the rear filter and had just a trickle of fuel. A blast from my air compressor in the hose and into the tank cleared whatever was in it and had a TON of free fuel flow. Problem solved (for now). I need to clean the tank and find out what is in it. The fuel flow should be very brisk, even at the bleeder past the front filter.
 
   / Kubota BX25 sputtering under load (not fuel filters?) #52  
Same issues - changed the first fuel filter (which was clean) and it seemed ok for a while, then same same sputter after a while under load. Mowing season started and issue returned. Pulled the air filer, which was clean but dark, and cleaned it out with compressor and noticed a bit of filth come out but filter seemed OK. Long story short, popped in a new (white and clean) filter and no more issues since replacing the old (way dark grey five year old but cleaned bi-annually) filter. Lesson learned... Change those air filters.
 
   / Kubota BX25 sputtering under load (not fuel filters?) #53  
Same issues - changed the first fuel filter (which was clean) and it seemed ok for a while, then same same sputter after a while under load. Mowing season started and issue returned. Pulled the air filer, which was clean but dark, and cleaned it out with compressor and noticed a bit of filth come out but filter seemed OK. Long story short, popped in a new (white and clean) filter and no more issues since replacing the old (way dark grey five year old but cleaned bi-annually) filter. Lesson learned... Change those air filters.

BX1850 worked fine for two one-hour mowings with the new air filter and maybe another couple hours of light loader wok at low RPM but went to mow again today and the sputtering issue returned after about 30 minutes. I'll swap out the down line fuel filter next to the motor and see what happens.
 
   / Kubota BX25 sputtering under load (not fuel filters?) #54  
I had the same problem with mine, but I was never very careful about letting crap into the tank when I was fueling ("Hey, it has two filters, what could go wrong?). Mistake, ended up having to remove the fuel tank (big job) and fishing out two large bugs which were occasionally clogging the fuel outlet. Lesson learned.
 
   / Kubota BX25 sputtering under load (not fuel filters?) #55  
I know this is an old thread, but, I'm going through this now. I've changed the filters and used fuel conditioner to remove any water. When I changed both filters I did not see any water and very little dirt. I felt it was something in the tank, as others have found, but, I don't understand why it should only happen after it has warmed up.
I can go up a hill when cold and not even get a hint of a sputter. And when I go up the hill it won't happen every time when it is warm. Also I can back up the hill without a sputter, as many times as I want to. Turn around, go up the hill forward and it falls on it's face. If it were the filters why could I back up the same hill with not problem? I thought maybe the furl pump was getting warm, but again why would backing up change it????
 
   / Kubota BX25 sputtering under load (not fuel filters?) #56  
It could be the fuel filters , I would also change the air filter. I just changed the air filter on my in-laws BX and the filter was pretty well plugged up. The connection on the filter housing to go to the cold air Inlet pipe was also messed up and I suspect was blocking the incoming air.

Aaron Z IMG_20180623_132719.jpeg
 
   / Kubota BX25 sputtering under load (not fuel filters?) #57  
Could also be the lift pump isn’t working.
 
   / Kubota BX25 sputtering under load (not fuel filters?) #58  
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.
 
   / Kubota BX25 sputtering under load (not fuel filters?) #59  
I would suspect that your lift pump is weak. Going up a hill forwards lowers the level of the fuel in the tank relative to the pump and makes pumping harder. Going in reverse, raises the fuel level with respect to the pump and you almost have a gravity feed situation.

Here is my list of things to check when apparent fuel flow problems rear their head causing shutdown, stuttering or power loss.
1) Check the air filter and fresh air plumbing to the filter housing.
2) If just power loss, check for exhaust restrictions in the muffler and the exhaust manifold
3) Disconnect fuel line to the IP and check for fuel flow, should be substantial when the lift pump is active.
4) Disconnect fuel line to the lift pump, should be a good flow
5) Disconnect fuel line from tank to the first filter, again should be good fuel flow
6) If 5) fails, there is an obstruction in the tank, either clean out the tank, or for temporary relief, blow back air into the tank
7) If 4) fails, either 6) or the primary filter is plugged, replace
8) If 3) fails, either 6), 7) or secondary filter is plugged, replace
9) Check all the fuel lines for cracks or pinholes, may show diesel contamination, maybe not, but will allow air infiltration into the fuel system.

Filters plugging up are the consequence of dirt or junk in your tank, or in many cases algae. Clean out your tank, and/or use an algae inhibitor in your fuel.
If possible, buy or fabricate a screen for the fuel inlet to your tank , something like the one shown.
fueltankscreen.jpg
Try to keep your tank full after each use to minimize condensation and water problems in your fuel tank. Water in the tank causes running problems if it is the in fuel stream to the engine, as well as causing rust problems on the fuel sending unit, and algae build up which will coat and clog your filters with black particles or slime.
 
 
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