1990 JLG 40ha hydraulic ??

[harveje]

Good morning,
My 40ha will not raise the boom as it should very slow to nothing at all. I can increase the rpm's and get some movement or activate the 12V emergency motor and it works pretty good.
1. how / where do I check for hyd pressure and at what rpm?
2. what valve stack handles the boom up / down? I can't see the dang schematic print
3. the boom down seems to work ok it's just the up and now the tower up is moving slow too.
I've set the rpm for the ground, platform and high speed per the manual (sometimes she wants to surge tho)
rotate, tele, platform rotate and tilt, steering seem ok.
And I have a bad or jacked up PQ controller one direction it's good the other there's a very small sweet spot or nothing.

Thanks

 

[harveje]

Does anyone have a clear diagram of 2792002 3120805 and where the hydraulic test ports are and the type of adapter or fitting I need?
Thanks,

 

[Delmer]

Sorry, I can't help you with the diagram.

If you have an emergency electric motor that works, and they both work through the same valve bank, what more evidence do you need? If you start it up and try to raise the boom at low RPM so that the hydraulics are stalled then shut it off, you should be able to find the heat, and the pump is the first place to look.

 

[harveje]

agreed but the swing, wheel turn, tele in /out, basket tilt and swing all work as they should. The hyd pump does not sound like it's stalling or dragging the engine down. IF I can figure out where the test ports are I'll start at the pump and work forwards. I'm thinking the lift and tower maybe on the 3 bank valve right under the oil filter area. Thanks for the help

 

[Delmer]

If it was just one function causing issues, I'd agree. You have the two hardest functions slowing down, coincidence? Unless I misunderstood "now the tower up is moving slow too"?

Don't assume there IS a test port, you might have to add a tee to test the pressure. The stalling I mentioned was the hydraulics stalling, no movement when the function is activated, so no oil flow so no cooling.

 

[harveje]

Thanks,
I don't fully understand the hydraulic circuits, do these system free flow or bypass fluid until a valve or solenoid is triggered? If so could fluid be bypassing the valve? I can feel the valve actuate when the toggle is activated I just don't know what the fluid is doing. And it seems to work better (not perfect) when the fluid is cold. I did find some type of quick connect close to the pump but unsure of the fitting type or size

 

[Delmer]

https://www.manualslib.com/manual/836859/Jlg-40h.html?page=10

Here's a manual. It's a three section main pump according to that page 10 that comes up, each section powers certain functions. Has to be a basic open center pump system, meaning the valve is open until a function is operated, then the flow is closed off and the "work port" is opened forcing the pressure to rise high enough to move the function, open the relief valve, cause internal leakage in a worn pump (what I called stalling), blow a hose etc.

Get a free download to identify threads, maybe quick couplers? here:
http://www.discounthydraulichose.com/category_s/55.htm

Since it works with the electric backup pump, the control valve should be fine. That doesn't mean there aren't other valves associated with that pump section that could do it, like a relief valve on that section of the main pump that wouldn't affect the electric pump.

 

[harveje]

Thanks,
Is the H hydraulics and wiring the same as the HA?

 

[OFF]

I've got some good 40HA diagrams (better than what's in the manual) but they are with a Ford gas engine, and only drive has a PQ controller. Everything else is toggle switches. I'll have a look at them tomorrow.
If you have all joy sticks though, these drawings won't do you much good.

 

[harveje]

That is GREAT mine has 1 pg (that is messing up too) for drive and the rest toggle with a ford vsg engine.. Thank you

 

[harveje]

Can you send me these diagrams? Please. Also checked a few pressures this morning. Unit cold, gauge on pump exit quick diss. low to mid rpm 2400psi, high idle 3000psi, switch to platform idle 1600psi. So the pump out goes to the 3 stack, tees and goes into the 4 stack valves. Are these valves feed thru? If I wanted to try to adjust pressure would I do that on the 4 stack bang bang dump valve? After unit is warm it takes allot of rpm's to get above 2500 psi. I just don't know if that's the pump or a valve letting fluid flow thru and not building up pressure. I guess I could dead head the pump with the gauge and see.
Thanks,

I've got some good 40HA diagrams (better than what's in the manual) but they are with a Ford gas engine, and only drive has a PQ controller. Everything else is toggle switches. I'll have a look at them tomorrow.
If you have all joy sticks though, these drawings won't do you much good.

 

[OFF]

harveje, turns out I only have electrical drawings on a 40HA, no hydraulic drawings at all. I don't even have a 40HA manual anymore. I'll get those drawings I do have scanned in on a big scanner (17 x 22 paper) and post them up. Each pump section and valve section should have its own relief valve. Drive has no valve section, all the drive control is built into the pump section.