L3902 hydraulic pressure test?
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Russell King
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Equipment
L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
It appears correctly plumbed into the system. It looks like the pressure may be just the system flow pressure (but I wouldn’t have expected it to be that high unless the three point valve (or some other valve) is lifting something).
Did you actuate the valve to move the cylinder (normally attached to that port) in the proper direction to get pressure to build up on the gauge?
Did you actuate the valve to move the cylinder (normally attached to that port) in the proper direction to get pressure to build up on the gauge?
Assuming you are holding the valve full open yes.
Move the gauge to the boom spool and try agsin.
If that yields the same result disconnect the pump supply hose coming to the valve and connect the gauge to the end of the hose. You will need to replace the coupler on your gauge with a JIC-08 male fitting.
Once the gauge is connected start the tractor, read and record pressure, and shut the engine off. Do not run the engine any longer than it takes to read and recorx pressure. Remove gauge and reconnect the hose.
Dan
North Idaho Wolfman
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L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Try it on the other spool.
The curl port can lie to you on pressure because of regen.
The curl port can lie to you on pressure because of regen.
I am sure the gauge is fine. Are you holding the valve open while reading pressure?
"Most people" dont understand pressure testing. Connect the gauge to the pump supply hose and see what you get there. Theres a reason why the two tests are not equivalent and they tell us different things.
What prompted you to test pressure?
Dan
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Oh I'm just piddling. Was trying to see if I could get a more lift capacity. I'm still trying to wrap my head around why this reading is so low. It's the 526 loader. Seems like the gauge is bad or I'm getting pressure relief way early. Spec on this machine is and around 2700 or something. It appears the machine is only sending 1200 to the cylinders what am I missing?
Yes to holding valve open. Rpms are wot and I'm trying to bump it and do when you get it to read more including tapping gauge.
Russell King
Well-known member
Lifetime Member
Equipment
L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
So that is the pressure while you are holding the valve open and the engine is full throttle = 1200 PSI?
If thats the actual pressure your loader would be a 90# weakling. I am trying to help you get a reliable reading if you will just follow the steps I have outlined.
Here is a video of a pressure test on a L3901. The gauge is connected to a valve port just like in your test. When the valve is operated the gauge spikes to 2400 PSI. That is the pump pressure at that port. But as soon as the valve is returned to neutral pressure starts to drop like a rock because the pump has been disconnected and the circuit cannot HOLD the residual pressure.
Your test point only works if you keep the pump connected by holding the vakve open. And even then there are two reluef vakves in the circuit and you dont know which one is controlling the pressure.
To measure the pump setting you need to test at the outlet block. Ditch that coupler and connect the gauge to the pump hose. Start the engine and that will give you a steady state unambiquous measurement of pump delivery pressure. I will bet dollars to donuts the pressure is way higher than your measurement.
Connecting at the backhoe outlet would be close to the same thing but your coupler may not fit and you still have two reliefs in the circuit.
Now do you understand?
Dan
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