Hello all! I am hoping I can pick some brains here.
I have the manuals but I am at a point where they don't really help me anymore.
I have resurrected this hyster after sitting for about 10 years. Changed all the filters and fluids. Ran and worked great for about a month. Now, it will lift and tilt when first started, but will get slower and slower irregardless of engine speed, till they stop working. Takes about a min or 2. Steering works the same throughout. I drained the fluid thinking maybe the in tank strainer was clogging up, as if you let the lift sit 10 min or so and restart the forks will work again, although the same as before. No change. I adjusted the priority valve on the pump, but I have to go all the way to the fork side, and steering won't work. The forks work great for about 5 min, then start to slow down again. There is no happy medium I can set it so steering and the forks work.
I'm kind of stuck now, thinking maybe something in the control valve, I don't think it is the pump, as the steering is good throughout and you can drive it around steering back and forth and it stays the same.
Maybe take the priority valve out of the pump and clean it?
Any thoughts would be greatly appreciated.
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Thanks guys, I was lucky. I removed the priority valve body from the pump, amd it was pretty sludged up. Cleaned it up and the inside real good, reassembled, and every thing works great after a little adjustment of the valve on the pump. Have driven it around all morning and moved a bunch of stuff around, all seems well. Thanks for the suggestions and so glad it wasn't a bad pump!
As brewski suggested you may want to get a pressure guage and use that to try and narrow down where the pressure loss is originating.
But based on your description and symptoms, your not wrong about the priority valve suspicion.
You might just be loosing system pressure due to the pump being worn out and when it gets hot it just stops building pressure and bypasses. (hence why you need to get a pressure guage and see whats happening).
According to the breakdown in the hydraulic manual this pump has 2 outputs, priority flow and steering output, there is a priority valve on it. So you are probably in the right place, just get a pressure guage and measure the pressure on the pump output, when you loose functionality i think you will see the pressure drop, probably when it warms up.
Once you verify this being the problem, get a new pump and it should work correctly again :o)
What is your pressure doing? It could be a relief valve. It sounds like the pump could be worn out. Steering takes less pressure and volume than the other functions.
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