Jinma 354 3pth will not lift

Tim Berframe · Apr 29, 2015

I am experiencing a problem with 3pth not lifting. This is the second time it has happened and want to focus on what I believe is the common cause. Last summer I drove over a pile of top soil to rip the sod layer off it with a box blade. As I drove down the steep slope, the box blade hung up on the top of the pile and took all the weight of the tractor. I suppose this over extended the normal range of motion by lifting too high.

I immediately noticed the lift wouldn't work. I changed all filters, screens, fluids, etc. In the process, I noticed that I had broken the pin off the lift arm press plate(see second photo). This is part of the draft control feedback linkage. Without the linkage properly connected, the lift has no limit. I am not sure why, but it started working normally again after welding the broken pin.

Fast forward to last weekend: Brand new tiller and quick connect. Spent some time getting quick connect and tiller mated to tractor. Lift working strong and normally. During final arm adjustments, I lifted it and the quick connect frame hit the fenders and cracked one. Lowered to ground and noticed the lift arm press plate pin laying on the ground. My attempt to weld it hadn't held. Re-welded it and reattached. Lift went to normal height. Started tilling my 1 acre. After only a couple lifts, the earlier problem returned.

It has no power to lift. At first, I could get about an inch of lift each time I jiggled the lever at the top 1/2" of travel. This would lift it about 1/3 its normal lift height. I could effectively 'jack' it up by repeatedly jigging the lift handle. Each row I did, the results got worse. Gradually the jiggling lifted less and less. Had to quit as it won't lift at all now.

The pump is fine (FEL strong and normal, steering normal). The lift cylinder is fine (blown seal wouldn't work intermittently and it does not leak down at all once it is up). That leaves the hydraulic lift valve (external with the lever attached) and/or the distributor assembly (inside the lift box). I am imagining a valve stuck in the wrong position that might have returned on its own the first time?

My question: Which of the two suspect parts would be negatively affected by over-extending the range of motion? (It appears that it resolved itself the first time) Has anyone else successfully resolved a similar problem? (Lots of unresolved issues on this and other forums that are similar)

I have attached photos. My parts book does not match what the tractor actually has on it so I can't describe with real parts names or numbers.

hazer36 · Apr 29, 2015

Try lift with lighter implement,tiller may be heavy enough to make your bypass valve kick out,to much pressure,you can add wahers to increase valve

hazer36 · Apr 29, 2015

After looking at pics better,it looks like you may have over extended piston on lift and scarred or torn the seal.maybe it will just be the bypass valve

Tim Berframe · Apr 29, 2015

Would the bypass valve be internal or external? I have no diagram of the external and do not know if my internal diagram is correct (everything else concerning the lift box is incorrect)

hazer36 · Apr 29, 2015

release valve is external,will be a hex head bolt next to lift handle,you can see it in pics,it will have a spring under it and washers and if I remember correctly a pointed pin that fit into valve,be careful adding washers too much pressure will blow pump seal

hazer36 · Apr 29, 2015

I had one stick before,just had to clean it well

Tim Berframe · Apr 29, 2015

Update: I removed the implement. With tractor running, the lift operated like before for 3 lifts then stopped altogether. With engine running and lift lever in raise position I manually lifted the arms. No hydraulic resistance whatsoever and it would not stay up - no oil going to the lift cylinder is my guess.

Opened both the hex head bolts on the lift valve. The forward one has a small spring inside. The aft one is the pressure release. There is one washer in there and nothing else looks amiss to me. Cleaned things and re-assembled. No change.

quicksandfarmer · Apr 29, 2015

I would focus on the feedback linkage before taking anything apart. I had one that was so out of adjustment the lift sometimes wouldn't lift at all.

The control on the 3PH is really very simple. Imagine the valve on the loader -- you push it one way the loader goes up, you push it the other the loader goes down. Imagine you and a friend are on opposite sides of the valve, you each have a hand on it and you're both pushing. If you push harder it goes up, if your friend pushes harder it goes down. That's how the 3PH works. There's the lift handle and the feedback link, each pushing on the valve. The feedback link is connected to the lift arm. You lift on the lift handle, the valve opens one way, the lift rises, and keeps rising until the feedback link is pushing back enough to balance the lift of the lift handle. You lower the lift handle, the valve goes the other way, the lift drops, until again the two pushes are balanced.

If you look on the right side of the tractor, you can see where the feedback link attaches to the right lift arm, and follow it into the valve right beside the lift handle. With an implement off you should be able to lift the lift arms by hand and see the mechanism move. I would start there.

quicksandfarmer · Apr 29, 2015

Tim Berframe said:
I am experiencing a problem with 3pth not lifting. This is the second time it has happened and want to focus on what I believe is the common cause. Last summer I drove over a pile of top soil to rip the sod layer off it with a box blade. As I drove down the steep slope, the box blade hung up on the top of the pile and took all the weight of the tractor. I suppose this over extended the normal range of motion by lifting too high.

I immediately noticed the lift wouldn't work.

Note that the lift arms are not attached to the lift cylinder. The lift cylinder pushes on them but you can't pull the cylinder by lifting the lift arms. So when you did this you couldn't have overextended the cylinder. You could have damaged the feedback mechanism.

With the way the feedback mechanism works, lifting the lift arms makes the feedback mechansim sense that the arms are higher than the setting of the lift handle, and it would try to lower the lift arms to correct. So if anything it would have lowered the cylinder. The cylinder is single-acting so you can't over-lower it.

It's possible that pushing the feedback mechansim outside of its range damaged the valve itself, I don't know a lot about how that works.

Tim Berframe · Apr 30, 2015

Quicksandfarmer,

Thanks so much for taking the time to respond. Your comments confirmed the line of thought I was on and I think I have solved the problem.

I read your comments and agree with you that I have not damaged the cylinder. That also confirms my earlier thought that the cylinder is not getting flow - the valve needs attention. I also thought "What if the broken linkage didn't cause the problem? What if the problem caused the link to break?" I was looking at the sequence of events wrong. Some other posts on here suggest that my lift doesn't work like others do (ie I should be able to hold the implement off the ground in a position part way between down and up - I cannot. All of the lift action happens in the last 1" of lever travel. The turnbuckle adjuster on the linkage has only a tiny amount of adjustment. I took it off and discovered that it is built to have a large adjustment range. I managed to get the lift to jerk up a few times and watched the linkage (I was going to adjust it like you said). Rather than move forward and backward, the linkage just bowed out sideways - no wonder it snapped off the pin.

So, the problem is that the shaft on the valve block that should pivot with the linkage is froze solid. You were right - the problem is in the adjustment of the linkage. I spent two hours trying to free it. I've marred up that stub shaft a lot but have it moving with about 50 ft-lbs of force. I'll work on it some more tonight. I dont want to heat it because I would think there should be a rubber seal on the inside of it. It has to turn with almost no resistance. If I get it turning, I save $200.

I am expecting the overall function of the lift to change once back together - I will confirm once I know.

Thanks again,
Tim