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Why does the engine pull down when I engage the hydraulics?
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dpilot83
Posted 3/3/2021 09:26 (#8870037)
Subject: Why does the engine pull down when I engage the hydraulics?



I use my JD 4430 for unloading grain bags.

The bag unloader has a hydraulic valve stack on it. I engage a hydraulic remote in the cab to provide hydraulic flow to the valve stack on the bag unloader.

Even when no hydraulic functions are being used on the bag unloader, engaging the hydraulics in the cab does NOT perceptibly pull the engine down.

I also have a Bag Lady (a hydraulically drive grain bag roller) mounted on the loader for managing the waste grain bags. It also has a hydraulic valve stack on it. One lever rolls the bag and one lever works the spears that stab the bag or release the bag.

I provide hydraulic flow to the bag lady valve stack with the grapple circuit on my John Deere joystick setup.

The joystick is fed by power beyond on the tractor. Returns back to the filter.

Whenever I engage the third function lever on my joystick, if no functions are being used on the Bag Lady it is VERY obvious that the lever has been engaged because the engine pulls down by several hundred RPM.

I assume that if the engine pulls down, a LOT of hydraulic heat is being generated. The bag lady is not used for extended periods so it probably doesn’t matter but I would sure like to understand why it happens.

To me, when the loader is not being used the power beyond circuit is being dead headed and it doesn’t pull down then. Why should it pull down when I actuate the third function and essentially just dead head the power beyond at the Bag Lady valve stack instead of dead heading it at the joystick valve stack?

Maybe my Bag Lady valve stack is designed for open center tractors so maybe when it’s not being used it bypasses oil so maybe I’m pumping say 15 GPM through the circuit when I engage the third function in the cab? 

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