# How do I get my hydraulic pump to prime?



## DanielWilson

My 960's pump started spraying fluid out the side. So I rebuilt it. Then it didn't pump so I rebuilt it again ... then I took it to the shop and got it professionally rebuilt.

And it still doesn't pump fluid.

Even with the top plug out, I pour oil in there and turn the engine over. No oil comes out besides what dribbles because I slopped / overfilled it.

Between rebuilds, I drained and refilled the reservoir so it has lots of nice clean oil in it.

A few minutes ago, I started the engine, then put air pressure to the hydraulic dipstick area for several minutes. Still no pumping.

How do I get this pump full of nice new parts to get its prime?

Thanks!


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## jhngardner367

Have you checked the intake ,and exit lines,to make sure they're not plugged?


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## DanielWilson

No. How would I check those lines? They are not accessible from the outside.


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## jhngardner367

Can you post a pic of the pump?
If this is the hydro pump,Crack open one of the cylinder lines(loosen,only),and start it up,then actuate the cylinder,to see if fluid comes out.
If it still doesn't prime,then there's still a problem,either with the pump,or the pump drive.


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## DanielWilson

It bolts to a solid aluminum manifold that handles both pressure and suction lines. If I unbolt from there, I likely won't align the gear right with the camshaft gear that drives it.


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## jhngardner367

In that case,there has to be an internal problem in the system.
Chances are,there's a restriction or a valve that has failed.
That may be what caused the pump to leak,in the first place. With no place to go,and the high pressure,,,,, boom !
What about the line to the control valve,from the pump?Can you check it there ?
Never mind. Just saw what you're talking about. Enclosed system.
the only thing I can think of is a filter failure,or a restriction in the intake.


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## DanielWilson

Well, I'm checking at the pump that it's not pumping anything.

See, it has a port on top ... kind of for bleeding the system, I think. Some suggest putting a pressure gauge on their and it should register 2000+ PSI when running. Just cranking the engine it should squirt some oil out.

On mine, just cranking, NOTHING happens out that port.

Maybe I'll pull the pump off and try some air pressure back down the suction side to see if I can clear a blockage.

Thanks for helping me brainstorm.


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## sixbales

Howdy Daniel,

Good to see you back on the forum!

Quote: "Maybe I'll pull the pump off and try some air pressure back down the suction side to see if I can clear a blockage."

I think that this is a good idea. There is a suction screen in the bottom of the reservoir that may be plugged.  There are also O-rings on both ends of the manifold that may be allowing air entry into the suction tube. Remove the filler cap on the hydraulic reservoir so you don't damage any internal seals with air pressure. 

When you had the test plug out of the pump did you see any evidence that the pump was moving internally with engine rotation? The reason I ask, maybe the drive gear on the camshaft has come loose? When you pull the pump, check the drive gear on the camshaft for looseness. I attached parts diagrams of the engine for you to see the drive gear.


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## DanielWilson

Thanks for the suggestions, Sixbales. Also for the diagrams.

That piston-type pump is definitely mine.

I've removed the proof-meter cable and watched as I cranked to verify the pump is being turned my the camshaft gear. But with the plug out, the oil I added to the plug area was barely agitated when I cranked. I wondered if somehow the pistons weren't actually being pushed ... but I don't think that's what that means. (Also, if that shaft is turning, the wobbler will push the pistons. Replacing the wobbler shaft was part of the most recent rebuild.) I think that the valves aren't opening b/c the pump isn't grabbing any fluid. Going back to ... the pump is likely OK, but not getting a prime.

Am I thinking straight?

I'll try the air pressure this evening.


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## sixbales

Is your tractor sitting out in the cold where there may be ice in the suction??

Here's another thing to try: Get a hose barb/nipple that will screw into the test port of your pump. Then run a clear plastic tube (1/2") back to the filler port of your hydraulic reservoir. This presents minimal backpressure to the pump whilst you are trying to prime it. And with clear plastic tubing, you can see what's happening


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## DanielWilson

I tried it with the port open. That's no back-pressure.

And it's garaged above freezing.

I ran air pressure into the suction side from where the pump mounts. Air came out the filler port as fluid audibly bubbled. I added oil to the manifold, then to the pump and put it all back together. I started up and put air pressure to the dipstick hole.

Still no lift ... and no oil out the pump port when I removed the plug. But the air pressure was enough that fluid started leaking out the transmission cover.

I'm so confused ...


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## sixbales

QUOTE: "Still no lift ... and no oil out the pump port when I removed the plug. But the air pressure was enough that fluid started leaking out the transmission cover."

The suction and pressure tubes both run through the bottom of the transmission, and have been known to develop leaks. One method to fix this problem is to install/epoxy new tubes inside the old ones. 

Is the transmission full of oil?? Gear oil or UTF? 

I'm going to the hunting lease, and will be out of touch for a couple of days.


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## sixbales

Besides the possibility of a leaking suction tube in the transmission, it could also be a leaking shaft seal between the hydraulic reservoir and transmission. 

Leakage of the pressure/suction tubes in the transmission is fairly common, particularly the pressure tube due to high pressure applied. Remember this tractor is nearly 60 years old. 

I have a plastic brake bleeding hand suction pump that might be useful to suck fluid up into the hydraulic pump. You would have to make a tight fitting connection in the pump test port to establish vacuum. You will see fluid enter the small clear plastic reservoir on the hand pump.

A ported rubber plug might work, or drill a hole thru a pipe plug that fits into the test port.


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