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Cat 312b pump loading engine.

Tyler d4c

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The front pump will load the engine with any function being used. It only does on small movements of the controls. At full movement it seems to destroke the pump. In short it seems the pump over strokes right off the bat. Serial is 9hr00999. Its grey market 9gr seems to be the us equivalent. Any help is appreciated.
 

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TVA

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Check to see if Powet shift pressure increases on the front pump together with back pump. Otherwise it’s just sticking spool in front pump regulator. The B should have A8VO in it. You can try and look up the control schematic and test ports locations on line!

Worn cradle or leaking servo piston will do that too. It’s been a while and I don’t remember if that pump has orifices in that line which can be plugged and cause that! I know that pumps that on C series does have orifices!
 
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TVA

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Well! Looks like I was wrong! Does yours have KAWASAKI in it?
 

Tyler d4c

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Check to see if Powet shift pressure increases on the front pump together with back pump. Otherwise it’s just sticking spool in front pump regulator. The B should have A8VO in it. You can try and look up the control schematic and test ports locations on line!

Worn cradle or leaking servo piston will do that too. It’s been a while and I don’t remember if that pump has orifices in that line which can be plugged and cause that! I know that pumps that on C series does have orifices!
It has this style pump
 

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TVA

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That’s a Kawasaki K3V! The older ones had Power Shift tubes on the outside, if it’s your case then first check weather the tube that goes to front pump has an restriction in it.

It’s actually not that hard to swap regulators on that one ( just make sure that feedback fork will catch the pin ) and see if problem will move with the regulator.
Kawasaki calls Powershift “ Total Horsepower Control “
 

Tyler d4c

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That’s a Kawasaki K3V! The older ones had Power Shift tubes on the outside, if it’s your case then first check weather the tube that goes to front pump has an restriction in it.

It’s actually not that hard to swap regulators on that one ( just make sure that feedback fork will catch the pin ) and see if problem will move with the regulator.
Kawasaki calls Powershift “ Total Horsepower Control “
I'm not quite sure what you mean by the power shift tubes on the outside. Heres a picture of what I got
 

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TVA

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Nope! You gonna have to make sure that there’s no restriction between the cavity of that solenoid and pumps regulators, especially front one!
 

Tyler d4c

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Nope! You gonna have to make sure that there’s no restriction between the cavity of that solenoid and pumps regulators, especially front one!
We are doing of the passage for the power shift pressure right.
 

TVA

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Yep! The theory is because you said it does de stroke on full movements, so the Power Shift pressure applies longer and have time to overcome the restriction!

Or, did you checked the correlation between short movements of joysticks and the pilot pressure for the whole machine? Maybe something funky going on there? Because your Power Shift feeds of off pilot system.
 

TVA

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What do you have on front pump? Boom and bucket? Check weather if pilot pressure drops when you short stroke that joystick
 

Tyler d4c

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Boom bucket and right track on the front pump. Pilot pressure does drop 10 psi or so immediately then comes right back. Seems normal to and I have verified I have power shift pressure coming to the front pump regulator. Then help is much appreciated.
 

TVA

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Does it do it on travel too? Does it do it on only one function? Like only on boom or only on bucket? Does the pilot pressure drop when you operate the other joystick?!
 

Tyler d4c

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Does it do it on travel too? Does it do it on only one function? Like only on boom or only on bucket? Does the pilot pressure drop when you operate the other joystick?!
Yes does it on travel too. Pilot pressure does the same thing with the functions for the other pump
 

TVA

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Then it is probably not your culprit!
10 psi is not a problem if measured with good quality gauge with right resolution 0-600 psi.

This reminded me about the thread here: guy had 320B LL and he was saying he that he had no stand by pressure at all! Well at 0 stand by you start thinking about stripped splines, bad coupling or both pumps completely shut!
Well turned out his gauges was bad, and he did have 200 psi stand by, and that made world of difference!
Because now you think main relief! And that’s what it was!
So quality of instruments and righ resolution is very important!
 
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TVA

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Well! Give us a new information on Monday and me, and people quietly reading this thread will start brainstorming and get to the bottom of it!

When you will have your regulators off - pay attention to that fork!
 

Tyler d4c

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Well! Give us a new information on Monday and me, and people quietly reading this thread will start brainstorming and get to the bottom of it!

When you will have your regulators off - pay attention to that fork!
Will do
 

Tyler d4c

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Salix Pa
Well! Give us a new information on Monday and me, and people quietly reading this thread will start brainstorming and get to the bottom of it!

When you will have your regulators off - pay attention to that fork!
Will do. But I did a little more testing. I teed a gauge in to the sense lines coming from the pump and found the line to the front pump has 900 or 1000 psi in it till a control is moved to full movement. Where as the other sense line has zero or close to it. Then when the control is moved it goes up to 500 or so then drops right off again. Is this a cause of the problem or the result of it.
 
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