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Curtis B.
Curtis B., Technician
Category: Industrial Equipment
Satisfied Customers: 704
Experience:  Technican turned service manager on multiple lines of equipment used in industry.
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Hope this is the correct category. I have a JL G boom lift.

Customer Question

Hope this is the correct category. I have a JL G boom lift. Model t-350. It goes up no problems every time when the hydraulic oil is cool but as it is used about 45 minutes and the oil starts to get warm it can't seem to get past a crucial point on the lift. This problem starts slowly and gets worse as oil temp goes up and steadily and consistently gets to the point were it won't go past the crucial point PERIOD. Any thoughts on what may be causing this? Thank you, Dave.
Submitted: 2 years ago.
Category: Industrial Equipment
Expert:  Curtis B. replied 2 years ago.
Problem is a bad hydraulic pump. When cold it has enough pressure to lift the load, as it warms, pressure can not be held, and it won't lift. It is lack of pressure from the hydraulic pump. Pressure regulator would affect system at all times, cold and hot.
Customer: replied 2 years ago.
Hey Curtis,
A bad hydraulic pump is bad news to me and has me riggling a bit. I bought this unit from Home Depot rental. They were selling it because they had technicians work on it on three separate occasions to no avail.
I don't know how much a new hydraulic pump would cost but i would think big bucks. I hope you understand that I must eliminate all simpler things before I resign to a new pump.
Questions for you; would a pressure regulator stuck in a fixed position allow more oil to bypass when the oil got warmer? Is it possible for them to fail this way? Are the settings on the pressure regulator fixed or adjustable?
Thank you for helping me, Dave P
Expert:  Curtis B. replied 2 years ago.
Pressure should be adjustable at the control valve, But it should not be affected by oil temperature. If it were bad, it would not work cold. A pressure check with a test gauge, would be standard test. Test pressure cold, it should be in the 2500 psi range, then again when hot. You could then try to raise pressure with relief valve, but if pressure does not increase, it means pump is the problem. Be sure and set relief back where it was, or with new pump pressure will be to high and can damage new pump!
Expert:  Curtis B. replied 2 years ago.
JLG has on line manuals on their web site.
Expert:  Curtis B. replied 2 years ago.
https://csapps.jlg.com/OnlineManuals/Browse.aspx
Customer: replied 2 years ago.
Thank you Curtis. I will get a gauge and check the pressures...just have to figure out where to get one.
Also I did find those manuals on the jlg website but haven't had a chance to dig into them yet.
Thanks Curtis, I'll try those things. 😀
Expert:  Curtis B. replied 2 years ago.
Ok thanks. Please rate to close the question!