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 | d. brooks
Join Date: Posts: 1 
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2003-08-10 61424
I need help with the 3 point lift on a SD2203 with electric solenoids. The lift works up and down just fine until you try to pick something up with it. It will not pick up more than about 100 lbs. I have had the hydraulic system almost completely apart and cannot find what is wrong. It is not the main lift cylinder or the hyd pump. It has to be in the electric solenoids or one of the valves located in the same housing as the solenoids. Does anyone know what to look for or check next. Thanks for any help.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2003-08-10 61466
I can't help specifically with the solenoids but might be able to say something useful if the hitch is a conventional position control 3ph where the lift spool and poppet valves are operated by solenoid rather than mechanically. I might be more shaky on other type hitches. Well, lift spool and poppet valve clearances to the linkage generally are adjustable and the solenoid throws probably are too. If you know that it's a conventional position control 3ph or another type, you might say.
I'm curious whether the light load that the 3ph does lift stays up when the engine is off or if it rapidly leaks down? I'm also curious if the performance starts off stronger and then deteriorates? If it does leak down, I'm curious if turning off the flow control valve stops the leak down?
I know this isn't much help yet but more info would help. You might check the oil after the tractor has run awhile to see if it's frothy. A clogged filter or broken suction line can create similar problems. There probably is a safety relief valve in the 3ph that also could create the problem as could several of the valves in the 3ph. ....
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| d. brooks
Join Date: Posts: 1
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2003-08-12 61607
I will describe the lift assembly as best as I can. The lift lever activates 2 micro switches that one or close the electric solenoid valves. One valve seems to let fluid go to the top of the lift piston, the other seems to hold the lift in place. These solenoids are sitting on top of a valve body that has at least 3 valves in it maybe more. I was told that I could replace this valve body with a mechanical one if I could find one. The lift will stay up only if you close the flow control valve all the way. If you open it with the engine off it will leak down very slowly ( 30-45 minutes)if you leave the key turned on. If you turn the key off the lift drops all the way down very quickly. I guess the electricity to the solenoids is shut off. The lift will not work at all without the key turned on even if the engine is running. AS for as performance, the condition does seem to get worse the longer the tractor runs. The oil is not frothy while it is hot and this tractor has no filter, only a wire screen that I have cleaned. While the lift is trying to lift the load it seems like part of the oil is going to the piston and part of it is going back into the pan. It even sounds like oil gushing back into the pan while it is trying to lift. I thought a line inside had come loose. How can I test these valves to make sure they are working properly? Thanks for any help. ....
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| EFC Construction
Join Date: Feb 2002 Posts: 11 Pasco, Washington
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2003-08-12 61657
The solenoids are not the problem; from what you described they are working correctly. It is most likely a bad o ring on the 3 point piston. Not a hard fix, pull the cylinder head of and push down on the upper arms. The piston will pop out into your hand. The seal is usually yellowish white in color and they get brittle with age. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-08-13 61716
It doesn't sound like it has position control or the lift would activate to raise the lift back to it's position when the engine is running. I'll assume that it has valving similar to position control but without the position feedback. The poppet valve controls lowering of the 3ph.
I'll guess a variation on EFC's comment, which may well identify the problem and it does sound like the solenoids likely are working OK. From the description, it depends on which side of the flow control valve the poppet valve is plumbed. I think it's more common for the flow control valve to be between the lift cylinder and poppet valve. If that's the case then closing the flow control valve would keep the lift up if the poppet valve were faulty. With bad cylinder seals, it should still leak down when the flow control valve is closed. Could be some of each I guess, especially because I don't think a bad poppet valve that takes 30-minutes to leak down should affect lift power that much. On some tractors the end of the lift cylinder is fairly easy to see so leaking cylinder seals can be identified is oil is coming out the cylinder end or if it collects on a plate. I think with some tractors it just goes on ground.
Could be that the seals or safety valve don't hold much pressure, so they bypass oil during lift but the leak down is another problem. The seals should be pretty easy and that be a good thing to do on general principal. The safety valve also should be pretty easy it can be found.
I'm curious if the 3ph also leaks down fast when the key is off and the flow control valve is closed? It's probably a safety feature to prevent people from leaving their 3ph's up. If it still leaks down fast there's likely a separate passage for a bypass and a valve that is normally held shut by a key switch activated solenoid. There could be a third solenoid and valve that's not located on the control valve assembly and that could be the problem.
Sure is tough speculating about the existence of something and then trying to find what may not exist though. If a closed flow control valve doesn't stop fast leak down when the key is off, a safety feature may be part of the poppet valve, in which case there'd likely be several leads going to the popper valve solenoid.
....
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| EFC Construction
Join Date: Feb 2002 Posts: 11 Pasco, Washington
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2003-08-13 61735
The SD2203 does not have a safety valve for leak down, position control is done with amplifiers that receive feedback from the tiller,. It is a very simple two spool solenoid with pressure bypass and that is it. One spool for lifting the other for lowering. Flow control valve is on the output side of the cylinder between the piston and the spool. We work on Shibaura's everyday in the shop and this is a common problem with common symptoms. I wasn’t shooting in the dark or speculating. It is one of two things and the piston seal (not the seal on the cylinder head, the piston seal that keeps the pressure in the cylinder) is the easiest to check first and will most likely need replacing anyway. If the oil can blowby the piston in 30 min with no load then the idea that it cant lift real weight makes more sense… If that is not bad then we can move to the other culprit. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-08-14 61805
It's good to hear some specifics about the hitch. No, I didn't think you were shooting in the dark, but without knowing the hitch I could only theorize. We did arrive at about the same main solution. I thought the leak down tests were done loaded (with whatever weight the 3ph could lift) but maybe not. I don't know if 100 lbs. is a significant load for this hitch or if the presence of a load would change the thinking any.
I keep mentioning a safety pressure valve, which provides load shock protection on many hitches when oil is trapped in the cylinder, because that turned out the be the solution the last time I heard this particular problem. I don't know if this hitch has one in addition to a system pressure relief valve. If it does it'd be a strong candidate after the piston seals.
I'm guessing the rapid leak down when the key is off is normal, and understanding why probably isn't important to finding the problem. I'm still curious why the leak down rate changes when the flow control valve is closed if the entire problem is the seals or pressure relief valve but I may not entirely understand the valving. ....
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