Kubota kx080-3 hydraulics stalling engine

[posrepair2013]

I am working on a kubota kx080-3 v3307 engine with 8k hours.
What's happening is when u are running hydraulics its killing engine u dont even have to be digging if u run a cylinder all the way out of in and hold it for a second engine will stall.
It does it when machine is hot or cold.
I have by passed fuel system( installed my own pump, fuel filter , fuel tank)
Checked boost pressure the highest it gets is like 15 psi before it dies (seems a little low to me)
I'm waiting on a compression test fitting just because I want to eliminate engine before I go to hydraulics.
It does blow a little black/grey smoke when it loads up before it dies.
Any suggestions or advice would be great thanks

 

[Vetech63]

Does it stall and die with every function? Does it run smooth with no smoke at high idle? I would check your turbo condition first. Pull off the air intake hose at the turbo and look at the internal impeller. Is it oily or the edges of the blades scraped? Does the shaft move excessively?
Bypassing the fuel system as you have only eliminates the suction side of the system. You could still have a pump or injector problem.
I'm not familiar with the hydraulic system in your machine. Is this a load sensing piston pump system? I cant imagine this being a hydraulic issue unless......when the pump strokes it cant move oil, meaning maybe a return side restriction? Something would have to block flow straight from the pump. I really need a little more info.

 

[Tinkerer]

I can't help you with the Kubota.
But, I like your username !

 

[Vetech63]

I can't help you with the Kubota.
But, I like your username !

LOL....I just noticed that!

 

[posrepair2013]

Yes it stalls with every function, runs smooth , no smoke untill u load it up.
And yes I just eliminated low pressure side.
I did check turbo very little oil , no play and blades are perfect.i have not done anything with hydraulics yet my next step is compression but I have had simular issue in past where it was injection pump.
But it's expensive so I just want eliminate as much as possible.

 

[posrepair2013]

Its is a load sensing piston pump I noticed today when I was over at machine that the tank does not hold pressure due to cap cracked.
But that would cause slow hydraulics I would think but definitely will damage pump being piston style pumps do not have the ability to suck fluid correct?

 

[posrepair2013]

Another thing I checked today was the return pressure at inj pump koeo there is constant pressure out of pump it does not crank long though.
I have had issues in past with pumps returning more then they should I can not find a test to be sure of it in manual.

 

[posrepair2013]

Anyone have any input??????

 

[Dave Neubert]

Sounds like the hyd. pump is not unloading

 

[posrepair2013]

Thank you for response I pulled pump today that's what I came up with.

 

[Little Mule]

Hello Posrepair 2013

I have a kubota KX 080-3 with same symptoms. I was wondering what turned out to be problem with your KX 080?

 

[Gchartrand]

I've had this issue before with my kx. Change all fuel filters again. Make sure the fuel strainer out of the tank is super clean. Ifnit does it again, you have yo clean out your fuel tank. It's not sucking correctly or returning. These motors are not that complicated. It's something simple.

 

[Little Mule]

Thanks, i did change all the fuel filters, my first thought also, no change. Problem is defiantly hydraulic. ISomething with the load sensing and flow management. I 'm planning on removing hydraulic filters and cutting them open to see if there is any metal inside. Just eliminate possibility of a pump failure.

 

[Gchartrand]

That's sucks.

Make sure you replace the hyd pilot filter as well.

 

[Mobilewrench]

I don't work on many Kubotas. But 8k hours is a lot for one of those engines. If it stalls with every function with a fully independent fuel system; then I would only be looking at the main relief on the valve body or, more likely in my mind (as you said in the original post) compression in the engine. But 90% of the equipment that I work on are low altitude. And at higher (or even normal) altitudes the first symptom of poor compression is a hard or extended start.

 

[Terence Bryan]

good night posrepair2013 I am having the same problem with my kx080-3 where the hydraulics shut down the engine did you find the problem

 

[Little Mule]

My problem ended up being the third pump, which is gear pump, had gone bad. When i did flow test on that pump, it was about half of what it should be. This didn't repair the stall issue completely but definitely improved performance of machine.

 

[Terence Bryan]

thank you very much .

 

[Delmer]

Its is a load sensing piston pump...

this might be the key, something in the load sensing system not functioning correctly. Could be as simple as a bit of debris, broken o ring, or small internal strainer that's plugged. This would be a good place to invest in the factory repair/diagnostics manual. The engine blowing some visible smoke while stalling is an indication that it IS getting enough fuel. The original thread was a year and a half ago, might not get any response.

 

[InsleyGuy]

The OP has not been on the site since Feb. 2021