Backhoe Pressure check on JW03 backhoe

Johnny P · Mar 16, 2009

Ron j

Engaged pump, dismounted from tractor and stood at the side of the rear wheel. cheched flow across reservoir. Checked operation for stabilizer leg and it responded, operated lever for leg with pressure gauge and got reading of 500psi. Checked oil level and it was disappearing. In all no more than two minutes elapsed I would think.
My thoughts at the moment are, when I return from the U.K with my supply of oil I will do the following tests after rebuilding pump with new shaft seal.

1. Remove spring from check valve and see if I get any movement in a cylinder. I don't think I will as I did not before with the old/original spring in place. It was only when I replaced spring that I got any movement. The spring is not an identical replacement, so I am wondering if it is too strong for the check valve and this affects the pressure when a spool valve is moved or something like that. Unfortunately I have lost the original!

2. Insert a spring. I am hoping to get a selection to try as I do not know the specification for that spring. Check flow and try a cylinder.

3. Remove PRV and try as Ron Mar suggets. What I don't understand, the piece I cannot remove at present, if I get it out, how do you know where abouts in the valve it fits? How far up/down the valve do you insert it? Is there as "seat" for it to come up against. That would determine if it comes out through the top or the bottom of the valve. If it is a moving part and is stuck, what does it move/stop against as there are moving parts above and below it. I just can't visualise this being a moving part and how it fits/works in the valve.

I have just invested in another pressure gauge, this time for my blood pressure!!!

Thanks JOhnny P

J_J · Mar 16, 2009

When you are blowing a pump seals, that would mean that you are trying to push fluid in a deadhead situation, nowhere for the fluid to go. You either blow the seal or burst the pump. . Maybe a relief valve is not working. You should not see high pressures on cylinders not doing heavy work. Until you find the cause, you can put a relief across the pump to at least protect it.

RonMar · Mar 17, 2009

You could completely remove the check ball, and it should work just fine. It's only purpose is to keep a heavilly loaded cylinder from forcing fluid back thru the pump. You would have to put a VERY heavy spring on top of that check ball before it had any real effect on the flow thru the system.

Regardless of if the safety relief is working or not, if you are not working any of the spools, there should be NO real restriction on the flow thru the system. You may have a blockage in one of the lines to or from the control valve. IF you take the outlet line off of the pump that goes to the control valve, you should be able to blow compressed air thru the hose to the valve block, thru the valve block to the outlet hose and on into the resovoir. This flow should be relatively unrestricted. If not, you could have a hose with a collapsed liner that is restricting the flow and killing your pump.

Another indication of a restriction on the system would come when you engage the BH pump. As you let out the clutch, a restricted system would cause a decrease in the engine RPM. A free flowing system will have almost no effect on the engine RPM. I think if you had a collapsed hose liner or some other restriction bad enough to kill a pump, you would note a definite decrease in RPM when you engaged the BH pump.

When you get the pump rebuilt, I would reccomend running some fluid thru it without the valve block in circuit. The easiest way to do this is to disconnect the hose between pump and control valve where it enters the control valve. Take this hose end and put it into the reservoir filler nozzle and engage the pump. Just make sure the hose dosn't pop out of the filler hole(very messy

). Run it like this for a while till you are confident that it is not blowing fluid out a seal. This will eliminate the possibility that something else is killing the pump seal, such as a bent pump shaft.

glenndehaven · May 28, 2009

Johnny P, did you figure out your backhoe problem.Mine does the same thing and I have cleaned and adjusted the prv, filter,replaced pump,checked engagement lever,fluids. cylinders etc, still very poor hydraulic movement.I am out of ideas.

erj · May 28, 2009

glenndehaven said:
Johnny P, did you figure out your backhoe problem.Mine does the same thing and I have cleaned and adjusted the prv, filter,replaced pump,checked engagement lever,fluids. cylinders etc, still very poor hydraulic movement.I am out of ideas.

Have you checked the hydraulic pressure with a gauge? What was the reading?
RonJ

glenndehaven · May 29, 2009

I am working on getting a gage set up and will post when I get the info.

Johnny P · Jun 3, 2009

Glenndhaven,

Hello, Yes, I have just managed to get my backhoe working. I dismantled the valve box and cleaned it, including the PRV, several times. Stripped the pump down and rebuilt it. Put in new suction filter and new oil. All this to no avail. The only other part I replaced was the spring in the check valve assembly, which is above the PRV. I did this after reading about someone else who had been having the same problem as us and thi is what he did to fix his problem. I have been told that it could work without the spring, but it's there for a reason. I had bought an inline PRV to bypass mine if that was the problem which I thought it must be, but before going to the trouble of getting connections etc., I replaced the aforemention spring, I set my PRV as low as possible and with the help of a pressure gauge I kept adjusting it until I reached the desired psi. Thankfully it worked.
One problem encountered when doing all this is when I rebuilt the pump. I got the inner workings the wrong way round, easy to do if you don't make special note of how they came out, and after rebuilding and testing on the tractor I blew the shaft seal on the pump.

Good luck with it.

Johnny P.