Oil & Fuel Air in BX25 rubber fuel tubes

[Moldymike]

I have a 2 yr old BX25 with 133 hours. I use it mostly to cut my 3 acre lot with the mid-mower. The problem is it runs very rough to the point of stalling after running the mid mower for a couple of minutes.
I discovered a small hole in one of the three fuel tubes that connect to a T-joint, so I replaced them all with transparent fuel tubes (3/16" internal diameter) but no help. Also, I replaced one of the fuel filters located closest to the fuel tank. The other one was replaced a couple of months ago .

Suspecting air in the fuel line, I observed the air purge from the fuel tubes when I turn the key to the pre start position. Also, no air appears after starting the engine. However, a couple of minutes after engaging the mower, I can see air bubbles swirling in the fuel tubes, especially in the one connecting to main fuel plug entering the fuel injection pump. Of course when the bubbles appear, it starts to stall out.

Any thoughts about why air would appear when I engage the mid-mower?

 

[Deano]

Sounds like you checked the most common things. The fuel system bleeds itself. Have you checked the fuel tank for crapola in it? Some of the guys here have had similay rough running/stalling and they had stuff in the tank keeping fuel flowing. Not sure how the air is getting in though?

 

[radioman]

Hmm, first off not trying to be redundant, but did you check the new lines connections? perhaps the ends are not tight letting air in? second, Are you sure the clear replacement tube is diesel rated? As deano suggested, check tank- however, I understand due to odd shape tank its hard to check. I'd blow the outlet with compressed air to make sure there isnt crud or an leaf blocking the outlet in tank.

Are you absolutely sure the safety switches isnt kicking in making it stall out? The easy way to tell is raise hood and do whatever you were doing to make it stall out and observe the shutoff solenoid plunger. if it moving ---- safety switch or bad wiring.

 

[Bladehauler]

I had a bobcat skidsteer that would cut out ( kubota engine, not that it matters) turned out that the draw tube in the tank had a crack in it about 2"down.
just my .02 and something worth looking at

Hope this helps, good luck
C-ya

 

[Moldymike]

I changed-out the transparent flow tubes with new 3/16" id tube with larger outer diameter; thinking that the flow tube clips would be snugger should they be the culprit. However, the problem still persists.

Also, the stop solenoid is not engaging when it begins to stall, so I don't believe the safety switches are involved. In the past, I would have trouble with stalling on hillsides. I think it was due to my weight shifting, and thus triggering the stop solenoid, though I haven't verified this as it hasn't been a problem of late.

Yes. It is difficult to check for junk in the fuel tank. It appears that the fuel is drawn from the bottom of the tank, so I don't believe that the air leak is coming from the tank.

Perhaps a fuel injector nut is loose; If I owned a torque wrench I could check them, but I'll leave that for the shop to check, where I probably will be going next.

Hopefully, they can solve the misery.

 

[J_J]

With a good supply of fuel, there is no reason that you would have air in the fuel line unless caused by air being sucked in by vacuum.

If your tank supply is almost stopped up, the fuel line will have a vacuum on them

Blow the fuel line out and check that all the fittings are tighten.

Seems like my Kubota has a vent line in the fuel path and should be closed off when running.

Looking at the data from Messicks, I see about 8 fuel clamps from the tank to the injector.

 

[Moldymike]

I'll try your advice when I return from my trip. I may begin by blowing out each line segment starting from the first fuel filter back to the tank to see what happens.

If that process doesn't work, I plan to drain the tank and use a borrowed
boroscope to view inside of the tank for debris that may be settling on the intake.

I'll keep you posted and thanks for all your help!

 

[Moldymike]

I blew out the fuel line from the first filter back to the tank, and then got good fuel flow. I let the tank drain a bit through the fuel tube, then reconnected the filter. I then emptied the rest of the tank with a vacuum hose. After refilling the tank with fresh fuel, all seemed to be back to normal.

I did scope the emptied tank with a boroscope, but did not find anything unusual. I was able to view the fuel sensor unit, but again, nothing unusual.

If the problem happens again, first I will open the banjo (air bleeder) bolt to see if that solves the problem. If that doesn't help, then I'll blow back the fuel line to the tank.

Thanks for all your great suggestions!