BX25 runs rough when warm

[Jasonblu]

Hi there. Great forum you all have here. Thanks for having me.

So, My BX25 has 313 hours on it and Has worked perfectly till now. Starts and runs fine (maybe sounds a little "rough" but hard to tell.) All features work just fine etc,... for about 15 minutes then it starts to run rough, nearly stalls under load. Disengaging mower deck and/or letting off on the fwd or back pedal also lets the engine return to normal idle but does then start to stall some randomly even if it's just idling, but putting a load in it definitely causes it to go into a near stall faster than just at idle. Turn it off let it cool overnight and the tractor works fine the next day till about 15 minutes of use. Repeat symptoms.

What it's NOT so far.

Gas cap. Same symptoms on or off
Fuel filters. Changed both. No improvement.
Coolant. Perfectly green and topped off. Temp gauge Does not indicate any overheating situation.
Air filter. Was rel dirty but I Changed it.
Watery fuel: I added full tank of fresh diesel plus a water remover additive in case I had water in my fuel.
Fuel pump: you can hear it chattering like always when the key is turned to the accessory position. (Side question: Do these pumps degrade over time or get to where they work poorly when warm or are they more likely to work great then just complexly fail).

Read some forums where people pointed to a rusting fuel Gauge sending unit in the gas tank. My fuel gauge seems to be working properly. If it is rusted away would think it wouldn't work right. Maybe some rust had faked off but not enough to make the sending unit fail just yet?

i called the closest dealer who's an hour and a half away. After hearing a summary of what I wrote here he wants to remove the gas tank and see if there's debris in it. About a $400 job with no guarantees.

My question is if it's debris in the gas tank what would operating temp have to do with it? Why is the supposed debris only clogging the fuel lines when the tractor is warmed up? Not feelin that as the answer just yet.

What would you all suggest I look at next before moving heaven and earth to get the thing to the shop and drop $400 on a maybe.

Thanks y'all.

J

 

[100 td]

Pull the line off after the fuel filter and run into a bucket and run the pump and cycle the fuel through the tank and see if there is good flow continuously. It is possible that something is blocking the lines. However I'd also check the hydraulic oil by dipstick, and also 'crack' or loosen the drain plugs to see what dribbles out, water or clean oil, do this after it has been sitting overnight without starting it. You could have a problem in the hydraulic/HST circuit that is heating up and binding as well, hopefully it's just a fuel issue..........

 

[Jasonblu]

Pull the line off after the fuel filter and run into a bucket and run the pump and cycle the fuel through the tank and see if there is good flow continuously. It is possible that something is blocking the lines. However I'd also check the hydraulic oil by dipstick, and also 'crack' or loosen the drain plugs to see what dribbles out, water or clean oil, do this after it has been sitting overnight without starting it. You could have a problem in the hydraulic/HST circuit that is heating up and binding as well, hopefully it's just a fuel issue..........

Thank you. I'll give all this a try.

Question: is there by chance a fairly simple way to completely detach the HST load from the engine so as to isolate the two systems?

 

[cerlawson]

My BX has been through a bunch of checks to see why it quits when running. Tank has been out and cleaned, among other things. Found no crap in tank. Finally I removed the beginning fuel filter and installed a larger one on the outside of the frame. See a U tube video on how a Canadian did this. Also changed the fuel pump. I tested two factory pumps that seemed to be weak, meaning if fuel tank level was low there was not enough push of the pump. The pumps tested at only 3 psi. Tore one apart and see it is s simple back and forth piston which easily can wear out. These cost $150 from dealer.

Bought a new fuel pump by going to e bay and punching in a search for HEP-02A and a bunch came up as low as under $10.. This design is different from the Kubota furnished pumps. I bought one selling for $19.90 free shipping.. It tests at 6 psi. Had to open up one side of the mount for fitting the larger screw (a way Kubota makes sure you install it right). So far with only a few hours on things this seems to have solved my fuel starving problems.

 

[cerlawson]

You might check where they come from. Mine took over a week to ship. Came from Hong Kong, China.

 

[Jasonblu]

My BX has been through a bunch of checks to see why it quits when running. Tank has been out and cleaned, among other things. Found no crap in tank. Finally I removed the beginning fuel filter and installed a larger one on the outside of the frame. See a U tube video on how a Canadian did this. Also changed the fuel pump. I tested two factory pumps that seemed to be weak, meaning if fuel tank level was low there was not enough push of the pump. The pumps tested at only 3 psi. Tore one apart and see it is s simple back and forth piston which easily can wear out. These cost $150 from dealer.

Bought a new fuel pump by going to e bay and punching in a search for HEP-02A and a bunch came up as low as under $10.. This design is different from the Kubota furnished pumps. I bought one selling for $19.90 free shipping.. It tests at 6 psi. Had to open up one side of the mount for fitting the larger screw (a way Kubota makes sure you install it right). So far with only a few hours on things this seems to have solved my fuel starving problems.

Interesting. I'll have to look into that. I wonder how that would affect a warranty. My bumper to bumper has expired of course but still under power train one.

 

[Huey6]

Same issue the my BX25 at 240 hours. New aft filter restored power for a few hours then back to bogging down under load. Removed the line to aft filter (pinching off line with small vise grips) and then when ready, released the pliers and shot compressed air though line back up into the fuel tank clearing the line. That was 40 hours ago and have not had an issue since. I am convinced it has a rusting fuel sending unit. I expected additional issue some time in the future but rather than replace the tank and unit I am just going to at a 5/16" tee to the line so I can blow it out more easily next time this happens.

 

[Jasonblu]

Same issue the my BX25 at 240 hours. New aft filter restored power for a few hours then back to bogging down under load. Removed the line to aft filter (pinching off line with small vise grips) and then when ready, released the pliers and shot compressed air though line back up into the fuel tank clearing the line. That was 40 hours ago and have not had an issue since. I am convinced it has a rusting fuel sending unit. I expected additional issue some time in the future but rather than replace the tank and unit I am just going to at a 5/16" tee to the line so I can blow it out more easily next time this happens.

when you say same issue, it would work fine under load until everything warmed up or it bogged under load even when cold.

How did/does your fuel gauge behave?

 

[Tooljunkie]

Dirt clogging outlet screen. A gravity flow test may help you identify the problem.

 

[Jasonblu]

Dirt clogging outlet screen. A gravity flow test may help you identify the problem.

can you (or someone) elaborate? not familiar with a "outlet screen" or how to do a "gravity flow test". Thank you!

 

[Daren Todd]

You disconnect the fuel line from the first fuel filter. Put end of hose in a bucket, and let the fuel gravity feed out of the tank. If it's flowing a full stream, then there isn't a blockage in the tank. If fuel just trickles, then something is restricting the flow out of your fuel tank

 

[Jasonblu]

You disconnect the fuel line from the first fuel filter. Put end of hose in a bucket, and let the fuel gravity feed out of the tank. If it's flowing a full stream, then there isn't a blockage in the tank. If fuel just trickles, then something is restricting the flow out of your fuel tank

Ok. Gotcha. Makes sense.

what would be spooky is if it flowed good when the tractor was cold and trickled when warm. What would cause that? (Thinking ahead here).

 

[Daren Todd]

You didn't have someone accidently add gas to it did you? Had a coworker accidently grab the wrong spout at a gas station and topped up his power stroke with gas. Truck would run fine till it warmed up.

 

[Jasonblu]

You didn't have someone accidently add gas to it did you? Had a coworker accidently grab the wrong spout at a gas station and topped up his power stroke with gas. Truck would run fine till it warmed up.

Definitely not but I can see where you are going with that. Thanks for suggesting it.

 

[Jasonblu]

UPDATE: cracked the HST filter as suggested. Only trans fluid came out. No watery yank goodness. Changed the filter and fluid while I was at it. Noted it was very low on udt2. Roughly 7 liters in there when there should be about 11. Put all I had 2.5gal/9.46 liters in. Getting more to top it off. Was hoping the low fluid was causing the stalling due to HST overheating. With 9.46 L in it still starts stalling once it's warmed up.

Next I tried testing the fuel pump. Removed the line just before the second filter (the one con the side of the engine). Turned the key and it only dribbles. Here's a link to a video

https://vid.me/VxwX

so you all could see it and confirm its not enough flow.

Next I'm going to let the unit completely cool then try the pump again. If it squirts out with a nice flow then I think I found my problem. That would mean these pumps can degrade to where they underperform when warm. Back it an update soon.

 

[D2Cat]

Jason, an engine will not run with that little fuel. You are on the right track. Probably pump!

 

[Jasonblu]

SUCCESS!

Before buying a new pump I needed to verify I didn't have a clogged line or junk in the tank so I Worked my way back along the fuel line, disconnecting sections at a time, and blowing out each with compressed air. Got to the last section, the one that feeds fuel into the first filter and did the gravity flow test as recommended. Just a trickle came out. (The engine was still pretty hot warm btw) Aha. Blew air into it and at first felt a blockage then sort of a "pop" as whatever was blocking the flow cleared. Fuel started gushing out of the line (and all down my arms). Ugh.

My Best theory on why this clog only happens when it's warm is that the gunk is some sort of material that changes viscosity with temperature. Maybe algae? I would imagine that algae when cold is harder and let's fuel pass but when warm it sort of "melts" and creates a blockage? Who knows.

Now, anyone know of a way to remove algae (and or other debris) without yanking out the fuel tank?

As for finding the cause I want to thank everyone here for their helpful input and suggestions!!!

 

[Russell King]

I believe you will need to search for a diesel algaecide like Stabil biocides or Biocleen


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[D2Cat]

Might see if you can locate some Star-Tron Enzyme Treatment. Amazon has several listings if you can't find something local.

 

[cerlawson]

My experience with Stabl diesel biocide is this. I thought maybe I had algae building up. However, i still had problems with stopping when tank was about half full. No help using that even with all fuel in tank replaced.

A funny thing found. At abut 32 degrees or even somewhat higher temp this stuff gelled and would not pour. At room temp it pours. I think it clogged my filters.

Anyhow I now think my problem was weak fuel pump. Fingers crossed.