Backhoe backhoe movements

jinmafriend · Feb 16, 2007

before i ask my first question in this forum, i will thank you for all the great information and effort true all the threads in this forum. here i´d got a lot of advice before i bougt my new jm254. i hope i can to my best to return a little bit with my experiences in future.

i have a new lw-6 backhoe with done oil-change to AW32, PTO driven pump selectet 1000 rpms and run the engine while operating ~ 1600 rpms.

it is normal that i cant operate two movements together? in example when i boom up the arm with the left joystic the arm will lower in the moment i uncurl bucket (to unload) with right joystick.

same problem with ZL20 based FEL when i rise FEL the arm will lower in the moment i uncurl bucket at same time. it seems that the hydropump deliver not enough pressure? Do you have any idea?

thank you Peter.

dirtworksequip · Feb 16, 2007

Yes, most small hoes loose certain funtions when you try and use another. They just don't have the hyds set up and complexity of a larger industial machine. Some of the larger machines will even prioritise(sp) certain functions over others. And others have multiple pumps to keep up with hyd flow demand. I would say it was normal for your hoe.

dirtworksequip · Feb 16, 2007

Sorry, after rereading your post. There shouldn't be any downward movement of the boom on either the hoe or the FEL just because you are using another function. There must be something going on with the hyd flow. What to check for............I'm not sure. Hopefully someone else will chime in and give you some help.

SPIKER · Feb 17, 2007

the hoe and fel are both open center valves, if you are pushing the boom to go UP and the curl to CURL both will work but what some times happens is the fluid form the BOOM up will cause the CURL to move twice as fast because the BOOM CYLINDER fluid is actually pressurize to raise the boom, when the fluid sees that the curl is open then it lets the pressurized fluid escape into the curl cylinder back through the OPEN boom up valve and OPEN curl valve and into the CURL CYLINDERS. this is NORMAL for these types of systems.

THEY WILL both move at same time if done right, the FLUID FLOW pressure and the SPOOL VALVES are all tied together, that is the main problem. lots of practice will let you move them together with lots of patience. some functions can't seem to work too well. lots of it depends on what position the boom, arm curl are all at. if the boom is straight out and you try to move the arm & boom at same time the much higher force on the boom cylinder will simply push the fluid back into the arm and the boom will drop... I still mess up doing it but usually I'm pretty prepared for it to happen.

As far as the FEL I haven't experienced that as much but my CURL is up stream of the BOOM far as plumbing goes so maybe that is why? LIFT spool shelters the curl spool then maybe?

MarkM

jinmafriend · Feb 19, 2007

thank you for your answers.

today i checked my problem with backhoe again. i think i must have a lot of air in the hydraulic-cylinders of boom and arm because when the digger-arm is in i can push it out by hand. same with boom, when boom is down i can lift it by hand. but this dont work in the other side, for example when digger is out i can not pull it in by hand.

in both cases the hydraulic-cylinder is out and i can push the cylinder in by hand. anyone have a idea?

i think normaly the air should leave by self when operate all functions serval times, but it doesnt.

also can see some air-bubbles and foam in hydraulicfluid. is it normal that i can hear a hum by running the Jinma-PTO-shaft-hydraulicpump? ask because i can´t hear this sound on tractors hydropump.

thank you peter.

JohnS · Feb 19, 2007

I suspect your joystick control ZL-20 is causing some movement on the lift valve when you are only trying to do the curl operation. I have never seen the fel drop on mine, when doing a curl. I have the older 2-lever control. The joystick design is known to be a little sloppy.

As far as hoe, I don't recall any specific humming noise and if memory serves me, it takes a bit of working to get the initial air out. With the foaming, I suspect you have a suction side air leak and that is probably causing the problem. Make sure all connections from the pump back to the tank are tight. A bad pump could be sucking air, too. If the LW is like the JM hoe, all cylinders are 2-way, except for the sway cylinders.

BTW, did the dealer tell you to run the pto at 1000rpm vs 540? Not saying it is wrong or causing this, just haven't heard that before.

SPIKER · Feb 19, 2007

I believe he is running the PTO in the 540 selection but running the engine slower than rated pto rpm. I run my JW03 hoe at ENGINE SPEED 1000~1200 rpm, not the 2200 for rated 540 rpms out at the PTO..

I agree that there may be a suction leak letting air into his system? not for sure/ though. Mine is silent other than standard tractor noise, (perhaps HE should try the PTO on without any attachment or pump to see if the noise he is hearing is form PTO or from PUMP.

My HOE also has some of the same displayed faults that you can PICK UP the bucket curl some and or the boom though it is too heavy to really pick it up much. possibly running slower does not remove as much air from the cylinders. I've had mine all apart due to breaking one cylinder shaft/pin off from the boom lift cylinder when I was smacking dragging a big rock down in the creek bed.

hope this helps.
Mark M

JohnS · Feb 20, 2007

Mark,

The way I read his post was, he has the pto selector set at 1000, and running the tractor at 1600rpms. Maybe I mis-understood though.

Assuming the pump drive shaft speed is the same as pto speed, my calculations (could be wrong) are 727rpms. Calculation is based on full pto rpm at 2200 engine rpms. While that is high, don't believe it is causing the observed issue. It is just clouding it.

While I haven't used my JW hoe in a while, I don't remember having to run it at full 540 pto engine speed to get adiquite performance. I have never run it on 1000rpm pto selected. Now the LW might be slightly different. I was more interested in finding out if he was told to run at 1000 or it was done just to get it to perform at all. ie the higher rpm running is partially masking the real problem.

SPIKER · Feb 20, 2007

JohnS said:
Mark,

The way I read his post was, he has the pto selector set at 1000, and running the tractor at 1600rpms. Maybe I mis-understood though.

Assuming the pump drive shaft speed is the same as pto speed, my calculations (could be wrong) are 727rpms. Calculation is based on full pto rpm at 2200 engine rpms. While that is high, don't believe it is causing the observed issue. It is just clouding it.

While I haven't used my JW hoe in a while, I don't remember having to run it at full 540 pto engine speed to get adiquite performance. I have never run it on 1000rpm pto selected. Now the LW might be slightly different. I was more interested in finding out if he was told to run at 1000 or it was done just to get it to perform at all. ie the higher rpm running is partially masking the real problem.

John I believe YOU are right, I miss understood: i thought he said he ran ENGINE at 1000 rpms which is near to where I run mine but I'm in 540 PTO, I have not even USED my 1000 rpm pto speed yet

I think he may be over running his hyd pump at that speed if it is anything like mine he is.!
but I have the Jw03 hoe.
Mark M

tat2z1969 · Feb 22, 2007

The pump shaft turns at engine rpm not at PTO rpm speed. Jinma brand Backhoe pumps are made to be turned at 1200 to 1400 rpm.

"Jinma-PTO-shaft-hydraulicpump? ask because i can´t hear this sound on tractors hydropump." ??????????????????????????????????????????????
Jinma does not make a PTO pump.
if it bolts to the plate on the back of the tractor it is a direct drive pump requiring 1200 to 1400 rpm of engine speed.

if it is a pump on the PTO shaft that implements hooks to then it requires the engine speed to maintain 540 rpm to that shaft.

The shaft behind the 4 bolt plate on the back of Jinma tractors is engine rpm speed and does not change speed with the PTO speed lever, one can be in 1000 or 540 rpm on the PTO but the shaft where Jinma pumps bolts up is at ENGINE RPM and only changes with engine rpm.

If you hear a hum or buzz noise from the hydraulic's you are propably pumping air with the oil or you are just cracking the valve open just enough to cause a high pressure stream at the valve, but probably air, Check all fittings.