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Massey Harris & Massey Ferguson Tractors Discussion Forum
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Hydraulic Control Valve refuses to unload

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Aaron Ford

04-29-2008 05:20:30




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I have recently began using my 65 which has a rebuilt pump and a new control valve. I opened it up to see if anything was apparent. The control valve will not unload if the rollered lever is opened more than 1/8 inch. Up to this point it will operate smoothly. Implement goes up and down as it should. If the valve is opened further the implement raises until it runs out of travel and blows the relief valve. Pushing in the clutch will drop the implement, but as soon as the clutch is released, the implement raises again. The only was to reset it is to shut the engine off or leave the clutch in for an extended period. The control valve operates smoothly with no catches.

Do I have a weak control valve spring? Am I overtravelling the control valve? I hate to pull this pump again, but by now I am getting quite good at it.

Thanks,

Aaron

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Joe Ferguson

04-29-2008 07:16:38




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 Re: Hydraulic Control Valve refuses to unload in reply to Aaron Ford, 04-29-2008 05:20:30  
Hi Aaron

You may operate the control lever by hand (the one with the roller) if operation is ok then problem is in the cover control linkage.

Is the lever at the correct side of the roller ?
I remember reinstalled the lever at the wrong side but i do"nt remember the effects.

Good luck

Joe Ferguson



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Aaron Ford

04-29-2008 08:03:09




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 Re: Hydraulic Control Valve refuses to unload in reply to Joe Ferguson, 04-29-2008 07:16:38  
Hey Joe, thanks for the response. If the control lever is moved independently of the fingers, it acts the same way. The rollered control lever just goes slack and the system continues to pump full volume til the clutch is depressed or the engine is stopped. It acts like the spring does not have enough force to return the inlet valve to the closed position. I was unsure of exactly how the oscillator worked when reinstalling,so it very easily could be an issue. I reassembled it exactly as it came apart. I reckon I will be pulling the pump, but I have no found a supplier for the spring yet. 180940m1 is the part number. Thinking about going down to the hardware store and matching it up.

Not sure,

Aaron

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DavidP, South Wales

04-29-2008 10:35:15




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 Re: Hydraulic Control Valve refuses to unload in reply to Aaron Ford, 04-29-2008 08:03:09  
Hello Aaron,
I think you might be going in the correct direction towards the oscillator. If the oscillator is broken or disconnected (on the 65 the oscillator is made from aluminium, later ones were steel)the control valve may well stick in the 'pumping' position and cause your problems.
If you operate the pump lever slowly you can usually feel whether the control valve is sliding or you are just compressing the spring. I don't think for one moment that your problem is a weak spring. As to matching it up at your hardware store..... ..have you seen the spring? lol
Unfortunately it is a 'pump out' to verify the operation of the oscillator. Check that the yokes are fitted correctly and that the pump is free to turn.
Regards
DavidP, South Wales

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Aaron Ford

04-29-2008 15:14:25




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 Re: Hydraulic Control Valve refuses to unload in reply to DavidP, South Wales, 04-29-2008 10:35:15  
The lever via the ball ended rod actuates the control valve which is resisted by the spring on the other side. The spring is mounted in a tube that could be removed/replaced. When the valve sticks, the lever becomes slack so the valve still has the spring compressed. I also thought of shimming the spring if that is what is necessary. Right now I am going to focus on the oscillator. Can you describe its operation? I noticed the ring that follows the cam, but am at a loss as to what it does. Thanks,

Aaron

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DavidP, South Wales

04-30-2008 00:08:55




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 Re: Hydraulic Control Valve refuses to unload in reply to Aaron Ford, 04-29-2008 15:14:25  
Hello,
The purpose of the oscillator is to stop the control valve sticking. The operating ring provides a rocking movement which in turn rotates the control valve back and forth. Instead of a sliding motion it becomes a slight 'screwing' motion which makes it easier to slide.
DavidP, South Wales



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