4-150, Vickers PVB-15 pump

First thing to check was to bleed the air out.
Didn't help.

Second thing was to pull the plug and clean-and-check the poppet valve in the valve assembly directly below the pump. No dice.

Local mechanic said if that's not it, the problem is in the pump. But according to another website, this is a variable displacement pressure-regulated pump. Something about a regulator, a remote-control of some sort, and a start-up valve.

But I'm not sure this pump is factory. The pump's blue, the rest of the tractor's chassis is painted black!

So--what's on your 4-150? Does the pump have a Vickers tag on it?

1. Pump worked great, but a hose leaked a little. I replaced the hose, and the hydraulics quit. I still get great volume on the lines going to the oil cooler on the front of the tractor, but nothing else seems to function as it should--except the PTO, which on this tractor I believe is hydraulically controlled (though there is another pump for some other systems.) But on the oil-cooler lines, it pumps nice volume and pressure--that's how I've drained the 7 gallons out to service the tractor. 7 gallons out in about a minute or two, and it sprays like we have pressure, it doesn't 'glug' out like it's falling by gravity.

2. Oil is full. Checked that several times. Bled the system for air too, though I notice the oil itself looks kinda light brown like peanut oil.

3. Numbers on the pump label are arranged thusly (though nothing is well labeled, so it's hard to guess what means what):

      Vicker
432148       A/91/0
M   PVB15  LSGW 21  C 10 219

4. Since the paint doesn't match, I also suspect it's not the original pump. I'm not sure what sort of pump really should be on there.

My best guess is that the regulator on the pump isn't doing quite what it should.

At this point, I have an impressive lawn ornament. Without proper hydraulics, it's very difficult to steer. I wouldn't dream of taking it to the field in this condition, even if the remotes did work (they don't.)

The PTO is hydraulically controled by the main pump and is turning because the brake is not applied.

It sounds like your pump is not "going into stroke". You either have air in the system or the compensator valve is stuck and not letting the pump stroke. The compensator valve is the cast piece on the outer end of the pump with the large screwdriver slot facing to the front. With the tractor running, note the location of the screwdriver slot, then turn the valve in or out a half turn, this may cause the pump to start working.

You could also loosen the pressure line coming from the back of the pump and bleed the air out there. Have someone else there to shut the tractor down when it starts pumping. If it was working OK before, then you shouldn't have a big problem now.

The replacement pumps are blue, I wouldn't worry about it not being the right one. WB.

I see a little blue thing hanging off this 'compensator valve' you mention, looks something like a tag. Not sure what it is exactly, but the family mechanic suggested that it might be a changing-this-setting-may-void-your-warranty kind of seal.

Not that it would have any warranty anymore, but nevertheless I'm a little cautious working with something I know next to nothing about and have no documentation for. After all, as far as I know this should be a simple air-evacuation problem! I just don't want to make matters any worse than they are--I'm really not terribly familiar with servicing White equipment.

(But this does make some sense to me. Air in the pump would cause the compensator to register a lower pressure because the air would compress, while the oil wouldn't.) Do I need some sort of pressure gauge arrangement to determine where to set the compensator back to? Because I don't have any such tool.

The PTO does appear to stop and start within a couple seconds as I move the lever inside the cab. I think that may be a noteworthy detail, since you said it's hydraulically controlled.

So...if I turned this valve and it caused the pump to start working, would that help to evacuate any air I couldn't bleed out? Or is this something I'll have to get used to doing everytime I use the tractor for the foreseeable future? Maybe alternately adjusting the compensator and bleed the air, and repeat?

Thanks

Just look at where the slot is positioned before you move it, ie 12&6 o'clock, 1&7, 2&8, etc and put it back to that same position. You will probably only need to move it a half turn or less to get some results. If you don't feel comfortable moving it, don't! You won't need to fool with the valve again just this one time to get the pump working.

There is also a smaller line above the comp. that is a drip line. It lets oil that leaks by go back to sump, you can loosen it and bleed air out also. I feel you just have an air lock in the pump and once you get it out you'll be OK.

Hyds can be intimidating so I understand your concern. If you don't have any mechanics that can work on this system, then you'll have to do it yourself. Sounds like you might need to buy a service manual. Where are you located? WB.

Cranking the tractor (or a slow idle) causes intermittent spurts of pressure in between dribbles from the pump at this fitting.

Local mechanic still insists that I didn't get the poppet valve pulled out far enough to verify proper functioning. He suggests replacing the valve. (The whole valve assembly directly below the pump.)

With the engine off you will get oil flowing from the resevior when the drip line is loosened.

I will get my shop manual and try to scan the valve assembly diagram so you can point out what you are calling a poppet. WB.