Have 54 NAA with piston pump. Having trouble with the hydraulics.
The main problem is that the lift suddenly stopped working. Here's a historical account, which stretches back about 2 years.
(Was posted on N Board. Re-posting here in hopes of getting more insights.)
Several years ago, I plowed my garden with a 2-bottom Oliver 3241 plow. Exciting times. Had no trouble lifting the plow but there were some odd things. I had always had some bobbing, even with just the blade---but only a few times a minute. But back to plowing. I wanted to use draft mode so I put the selector into the horizontal position, moved the control lever down, and started plowing. When I moved the selector, it would jerk the plow all the way up, briefly. Later that day, I was running a bush hog and 15-30 min later I noticed that the mower was lowering. Corrected several times with position control lever but eventually it was just dragging on the ground. I unhooked the mower and drove back to the garage.
I eventually was advised to do the usual maintenance---the cam follower pin, the pin that bears on the piston skirt (very bent), gaskets, etc. When I took off the lift cover, I found that the turnbuckle was not turned vertical. This could cause the linkage to jam. Fixed that and all of the other stuff. Also got distracted learning how to spray implement paint on various parts, built a bead blasting cabinet, etc. Then the wife signed up the kids for soccer, the basketball. Next thing I know, I'm coaching instead of tinkering. A year goes by. I eventually get the lift cover back on, find the bolts, re-wire the tractor, replace the starter, weld a lug back onto the block. You get the point.... trying to do too many thing at once.
Recently, I got it all together and found that the lift arms don't move at all. Tested for prime in the pump by running a hose from the pump to the filler hole on the sump. Pump seems fine. Checked for oil splashing down from the ram cylinder. None. Even checked for a spray against the front wall.
Verified that the back-pressure valve stud is seated against the o-ring on the ram cylinder. Safety valve down in the sump was not tripping.
Eventually, I blocked the back-pressure valve tube with my finger. Immediately, the lift arms move up, with no load, not even the rear links.
Now I suspect that the back-pressure valve is stuck open. I take it out and notice that there is a clear path between the ram-cylinder-o-ring contact and the tube. Did some light percussive maintenance and get the spool free.
https://drive.google.com/file/d/0B3wfQHEAycNcczFtdWExVkVTb1E/view?usp=sharing
After getting it free, I re-installed the back-pressure valve. It didn't seems to make any difference. Still can use my finger on the outlet and the lift works right away. So I guessed that the valve was breaking open below the FO-19 spec of 45 psi. I'd estimate that about 45 psi of finger pressure was sufficient to get the lift to go up, judging from the tube diameter and how hard I had to press. But when I press on the spool, when I was cleaning it, much less than 45 psi was required to depress the spool.
Now I decided to try putting a spring under the acorn nut. After trying several lengths, the lift appear to mostly work. However, it DRIFTS UP without any load. At first, I thought this indicated too strong a spring so I cut off half a turn until the spring pressure was very weak. Even with the weak spring, it still drifted up. If I removed the spring, the upward drift stops and the lift arms were inoperative---the original problem.
With the weak spring installed under the acorn nut, I noticed that if I stand on the lift arm (200 lb) and the control lever is down, it will drift down as fluid is released from the ram cylinder. If I raise the control lever, the lift will stop going down, corresponding to the position of the control lever. But it cannot lift me.
I started over with a much longer spring. The lift drifts up but if I stand on it, it acts normally. When the lever is down, the lift sinks. When I pull up on the control lever (still in position mode) the lift goes up. If I turn up the idle, the response is a little more snappy but the difference isn't huge.
Then, I figured, I can at least move the plow to the neighbors yard. Closing on this house is Friday and the Buyer is walking through on Thursday. No pressure. Hook up the plow with the tractor off. Start... pull back on the control lever and it lifts the plow, about half way. I put it down and try again and it doesn't lift as far. I get a pressure gauge and put it on the jack tapping port (on the lift cover). Try to lift again and get 200 psi. Subsequent attempts get even less pressure and almost no motion of the lift. I look into the filler hole and see fluid gushing when I move control lever up. I think I saw something like a 1/2" diameter stream toward the back of the tractor. Seemed like it was coming from near the control valve. JMOR suggested looking at the check-valve and after looking at this assembly, but after examining it, I do not think it would produce the type of spray pattern I observed. Also, I found a blown gasket between the ram cylinder and the lift cover. Could this be a result of excessive back pressure?
https://drive.google.com/file/d/0B3wfQHEAycNcTWZBd0dvU1YtUDA/view?usp=sharing
I got another back-pressure valve from ebay. Was 20 $ and I didn't have high hopes. It also looks stuck open... can blow through it without resistance. Nothing moves. It's rusty and smells bad. Oh well, it was worth a try.
Here's JMOR's drawing of the back-pressure valve:
http://i192.photobucket.com/albums/z232/JMOR_photo/NAA%20HYD/hyd_NAA_backpress_relief_flow.jpg
Can anyone make sense of this?
The main problem is that the lift suddenly stopped working. Here's a historical account, which stretches back about 2 years.
(Was posted on N Board. Re-posting here in hopes of getting more insights.)
Several years ago, I plowed my garden with a 2-bottom Oliver 3241 plow. Exciting times. Had no trouble lifting the plow but there were some odd things. I had always had some bobbing, even with just the blade---but only a few times a minute. But back to plowing. I wanted to use draft mode so I put the selector into the horizontal position, moved the control lever down, and started plowing. When I moved the selector, it would jerk the plow all the way up, briefly. Later that day, I was running a bush hog and 15-30 min later I noticed that the mower was lowering. Corrected several times with position control lever but eventually it was just dragging on the ground. I unhooked the mower and drove back to the garage.
I eventually was advised to do the usual maintenance---the cam follower pin, the pin that bears on the piston skirt (very bent), gaskets, etc. When I took off the lift cover, I found that the turnbuckle was not turned vertical. This could cause the linkage to jam. Fixed that and all of the other stuff. Also got distracted learning how to spray implement paint on various parts, built a bead blasting cabinet, etc. Then the wife signed up the kids for soccer, the basketball. Next thing I know, I'm coaching instead of tinkering. A year goes by. I eventually get the lift cover back on, find the bolts, re-wire the tractor, replace the starter, weld a lug back onto the block. You get the point.... trying to do too many thing at once.
Recently, I got it all together and found that the lift arms don't move at all. Tested for prime in the pump by running a hose from the pump to the filler hole on the sump. Pump seems fine. Checked for oil splashing down from the ram cylinder. None. Even checked for a spray against the front wall.
Verified that the back-pressure valve stud is seated against the o-ring on the ram cylinder. Safety valve down in the sump was not tripping.
Eventually, I blocked the back-pressure valve tube with my finger. Immediately, the lift arms move up, with no load, not even the rear links.
Now I suspect that the back-pressure valve is stuck open. I take it out and notice that there is a clear path between the ram-cylinder-o-ring contact and the tube. Did some light percussive maintenance and get the spool free.
https://drive.google.com/file/d/0B3wfQHEAycNcczFtdWExVkVTb1E/view?usp=sharing
After getting it free, I re-installed the back-pressure valve. It didn't seems to make any difference. Still can use my finger on the outlet and the lift works right away. So I guessed that the valve was breaking open below the FO-19 spec of 45 psi. I'd estimate that about 45 psi of finger pressure was sufficient to get the lift to go up, judging from the tube diameter and how hard I had to press. But when I press on the spool, when I was cleaning it, much less than 45 psi was required to depress the spool.
Now I decided to try putting a spring under the acorn nut. After trying several lengths, the lift appear to mostly work. However, it DRIFTS UP without any load. At first, I thought this indicated too strong a spring so I cut off half a turn until the spring pressure was very weak. Even with the weak spring, it still drifted up. If I removed the spring, the upward drift stops and the lift arms were inoperative---the original problem.
With the weak spring installed under the acorn nut, I noticed that if I stand on the lift arm (200 lb) and the control lever is down, it will drift down as fluid is released from the ram cylinder. If I raise the control lever, the lift will stop going down, corresponding to the position of the control lever. But it cannot lift me.
I started over with a much longer spring. The lift drifts up but if I stand on it, it acts normally. When the lever is down, the lift sinks. When I pull up on the control lever (still in position mode) the lift goes up. If I turn up the idle, the response is a little more snappy but the difference isn't huge.
Then, I figured, I can at least move the plow to the neighbors yard. Closing on this house is Friday and the Buyer is walking through on Thursday. No pressure. Hook up the plow with the tractor off. Start... pull back on the control lever and it lifts the plow, about half way. I put it down and try again and it doesn't lift as far. I get a pressure gauge and put it on the jack tapping port (on the lift cover). Try to lift again and get 200 psi. Subsequent attempts get even less pressure and almost no motion of the lift. I look into the filler hole and see fluid gushing when I move control lever up. I think I saw something like a 1/2" diameter stream toward the back of the tractor. Seemed like it was coming from near the control valve. JMOR suggested looking at the check-valve and after looking at this assembly, but after examining it, I do not think it would produce the type of spray pattern I observed. Also, I found a blown gasket between the ram cylinder and the lift cover. Could this be a result of excessive back pressure?
https://drive.google.com/file/d/0B3wfQHEAycNcTWZBd0dvU1YtUDA/view?usp=sharing
I got another back-pressure valve from ebay. Was 20 $ and I didn't have high hopes. It also looks stuck open... can blow through it without resistance. Nothing moves. It's rusty and smells bad. Oh well, it was worth a try.
Here's JMOR's drawing of the back-pressure valve:
http://i192.photobucket.com/albums/z232/JMOR_photo/NAA%20HYD/hyd_NAA_backpress_relief_flow.jpg
Can anyone make sense of this?