45 hydraulic pump help needed

The hydraulic pump is located in the right side of the tractor just behind the side PTO.

The pump can be set for all sorts of jobs so be sure that it is set up correctly for the job you need to do. There should be a decal on the battery box just above the pump that shows you how to set the pump up. The pump has four manual adjustment knobs. The most commonly used set up for me is the hold position setting. The lowest knob on the side of the pump is the drawbar adjustment. Its use is for pulling plows and the like and gives traction control. Turn this knob all the way into the body locking the plate into position. The second knob is on top of the pump on the side linkages. This is the hold position adjustment. Turn it so that it locks the two plates together, allowing them to move as one. The third knob is also on top but on the front of the pump. This controls the delay lift. Turn it all the way out until it hits its stop. The last knob is on the front of the pump about half way down. It controls the rate of lift. Turning it all the way out gives you fast lift. All the way in is slow lift.

If you are having the same problems I had, the pump isn't developing the pressure it should before the unloading valve pops off (also called a pressure relief valve). It worked fine without a load but could not lift anything heavy.

I first bought a pressure gauge (0-5000 psi) and installed it at the small port on the top front of the pump where the 'booster gauge' was normally attached. My pump was only developing about 1000 psi, less than a third of its 3500 psi rating and that wasn't enough to pickup even a 4x4 round bale of hay.

You'll have to pull the pump off the tractor (three nuts and two bolts) to access the front cover plate. Four bolts takes the plate off. The plate covers two cylinders, the first one has a the last manual adjustment knob I mentioned above, the rate of lift control. The cylinder without the adjustment contains the unloading valve. Pull the piston out of the cylinder. This is the valve seat assembly which has two o-rings outside and contains the valve seat internally. Watch out for the valve ball as it may pop or fall out unexpectedly. Next pull out the upper spring retainer. Watch out for shims falling off the underside of this retainer. Last out is the spring itself. The spring may be broken or may have weakened over the years, or the o-rings around the valve seat assembly may be leaking.

Adjustments are made by adding more shims on top of the spring to increase the working pressure. (if you put shims under the spring, be sure they don't block the off-center hole in the lower spring retainer.) Its trial and error here. I doubled the number of shims (a little over a sixteenth of an inch) and still need to reinstall the pump to see where this brings me. If it isn't enough, I'll have to pull the pump off the tractor again and add more shims. If its over 3500 psi by my gauge, I'll either have to pull some shims out or be very careful not to hit the end of travel on the rams and blow hoses (at best).

Of course your problem may be something else entirely, so get that pressure gauge installed as a first step. Mine was fairly cheap at $20.

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Sounds like you have at least two different problems going. First off, I have to assume you have checked the oil level. Low oil could cause the lifting problems (more on that later).

The fact that the lift would not drop, yet you were able to push it down suggests that the ram cylinders are sticking rather than a pump problem. Cleaning the rams should correct that problem.

A common problem with these older pumps is in the unloading valve. The system is designed to have 3300-3700 psi. The unloading valve spring can weaken with age and/or other parts can wear or break causing the valve to unload at much lower pressure.

There is no way to get to the unloading valve with the pump on the tractor. Drain the oil and disconnect the linkages to the pump. The easiest way I've found for removing the pump is the remove the remote ram steel line from the hold position valve and then remove the two bolts holding that valve to the top of the pump body. There should be enough play in the rubber lines to move the valve out of your way. The pump itself is attached to the tractor by three nuts and two bolts. Removing the pump from the tractor is a little tricky as it is a tight fit but by twisting it this way and that you can get the oil pickup tube and cam followers clear of the transmission and frame.

Now with the pump on your clean workbench (I always lay down a couple of layers of newspaper to soak up any oil) look at the front of the pump. There is a small access plate with a manual control knob through it held on by four 7/16 bolts. Remove the plate carefully as there are springs under it. The plate covers two cylinders. The first outer cylinder contains the control valves (this is the cylinder under the manual knob). The inner cylinder contains the unloading valve assembly.

The unloading valve assembly should pull right out (but if it is stuck you can tap it down lightly with a hammer and it should pop right up) be careful as there is a small check valve ball that may fall out the bottom of the assembly. Under that will be the upper spring retainer, a upside down bell shaped deal with a small rod (called a plunger) down inside the bell. (The plunger has a small hole drilled off-center on the upper end, the end that comes in contact with the check ball. Its gotta go back in that way.) Pull this out carefully as well since there are probably some shims on the backside that may fall off. Next is the actual spring (plus any shims that may have fallen off before you got the upper retainer out) and possibly some more shims under the spring. Inspect all the pieces for cracks or breakage. (I've got a tractor junkyard close at hand so spare parts are relatively easy for me to get.)

If everything looks OK, you probably just need to add more shims. I found a couple of M12 washers under the spring work very nicely. You do have to be aware not to block the off-center hole in the lower spring retainer. Reassemble everything.

A nice little trick for getting the access cover back on is to have two longer bolts (2 1/2 to 3 inch threaded all the way up the shank) with nuts turned all the way up to the head. Place the access cover over the cylinders and insert the long bolts. Now you can push down on one side and then the other, tightening the nuts as you go and work the cover down to where the original bolts will start.

Its trail and error getting the right number of shims to bring the pressure up to specs (3300-3700 psi) so be prepared to repeat this process as needed. (In your case you may want to start with three washers.) I'd also suggest putting on a 5000 psi gauge in the small port on the top front of the pump (where the traction booster gauge would go) so you can monitor your progress.

Of course you could have other problems, leaking check valves, etc. All of the check valves can be reseated with "a solid hit with a one pound hammer using a soft punch". The only exception to that is the unloading valve check ball. It can be reseated by pressing the ball into the seat with 5000 psi and then reaming the seat opening back to 3/32.

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Mine had the same "problem" when I got it. The previous owner had wire tied the control down. Turned out that that the pump wasn't setup for the right job.

The pump can be set for all sorts of jobs so be sure that it is set up correctly for the job you need to do. There should be a decal on the battery box just above the pump that shows you how to set the pump up. The pump has four manual adjustment knobs. The most commonly used set up for me is the hold position setting. The lowest knob on the side of the pump is the drawbar adjustment ("A"). It is used for pulling plows and the like and gives traction control. Turn this knob all the way into the body detent locking the plate into position. The second knob is on top of the pump on the side linkages. This is the hold position adjustment ("B"). Turn it so that it locks the two plates together, allowing them to move as one. The third knob is also on top but on the front of the pump's hold position valve. This controls the delay lift ("C"). Turn it all the way out until it hits its stop. The last knob is on the front of the pump about half way down. It controls the rate of lift ("D"). Turning it all the way out gives you fast lift. All the way in is slow lift. (I have mine set about halfway.)

Once you have the pump setup for the job you want to do, you need to adjust the linkages. (I'm going on memory here so hopefully someone will check me on this.) First with the tractor off move the lift control to the full up position. There is an adjustment just under the gas tank on the large linkage to the hydraulic pump. Loosen this and push the linkage down to take all the play out of the pump and retighten. Move the control back to the down position. Turn the second knob I mentioned above (the hold position knob "B") into the detent in the body of the pump separating the two plates and locking the inner plate to the pump. Now loosen the smaller linkage adjust which is on the outer plate so the rod moves easily but be careful the rod doesn't slide all the way out. Now start the tractor and raise the lift to max height and shut the tractor off with the control still in max lift. Stand on the lift arms and slowly lower the lift control until the pump releases completely. (This should be about halfway down the quadrant.) Now, being careful to not move the position of the control, go back to the outer plate and rotate it so that you can turn control "B" back out of the pump so that the inner and outer plates are again locked together. Being careful to not move the control linkages, rotate the plates counter-clockwise until you feel it click into a detent and tighten the small linkage adjustment.

You may have to tweak it here and there depending on how worn your linkages are and I don't recall the adjustments for the traction boost linkages down to the drawbar (and don't use them anyway as mine doesn't have the linkages) but that should cure your creep problem. The control may still creep up from full down to the detent but the lift will stay down. (I normally keep the control at the detent anyway.)

Hope this helps.