No cylindder pressure....

mrcaptainbob · Nov 9, 2013

The log splitter was working great until the cylinder wouldn't split the wood. It seems there's enough pressure to move the ram fore and aft and to cause the detent to work. Holding the lever at either direction to force a load does not change the engine rpm's or loading. The detent spring is not broken. It happened rather instantly. Was splitting oak and all was well until it got to a nasty. usually this 'nasty' part would not be an issue. Also, it sounds like there's a sort of vibration in the valve body. Is this a sign of:
* valve needing an 'O' ring kit?
* detent spring shims? (does not appear to be an adjustment. Just a cap over the spring with it's seal.)
* cylinder seals leaking?
* Pump issue? (Heaven forbid!!!)

I have no gauges to check pressures. It was recommended to squeeze one of the cylinder hoses and operate the cylinder to verify a bad cylinder seal. Also to slowly squeeze the pump output hose to see if it bogged the engine. Caution was given so as to not over squeeze and blow the pump. I did one of the cylinder hoses, but was reluctant to force it. Was concerned about lousing up the metal jacket and rubber and having to replace that, too. Didn't even try the pump output hose.

oldnslo · Nov 9, 2013

Do NOT squeeze any of the pressure lines to restrict flow. This will damage the hoses.

Splitting force is the result of pressure. Typically pressure loss is caused by relief valve stuck open, seals blown in cylinder or pump not turning under load.
Did the shaft key shear in one of the coupling halves? I.e. are you able to confirm the pump shaft is turning under load?

Cylinder seal test: fully extend the cylinder, remove the hose from the rod end of the cylinder. Plug the connection to the valve. Point the hose into a bucket and move the control valve to try and extend the cylinder little to no fluid should come out this hose. If you get significant oil flow the cylinder needs repair.

Relief valve: depending on the style you have it may be adjustable or shimmed. If adjustable you will need a gauge to reset the pressure. Most relief valves in directional spools are a simple spring on top of a poppet or ball. If a piece of debris gets stuck under this poppet or ball it will hold the valve open. Or the spring could also have broken.

good luck

mrcaptainbob · Nov 9, 2013

I like that idea, Oldnslo. I'll do that tomorrow. I checked the relief and it appeared clean. The spring is not broken. The pump shaft does turn. I'll verify that both sides are spinning the same. Thanks for the help.

mrcaptainbob · Nov 10, 2013

It took a while, but I extended the shaft fully. Disconnected the hose at the shaft end of the cylinder. Left all hoses connected to control valve. Did not plug cylinder end of hose. Started the motor and applied pressure as if to extend cylinder. No oil came from cylinder port. It also did not bog the engine. Reconnected h0ose to cylinder. l will verify again that the pump shaft is spinning in synch with motor shaft when under load. After this....do I try shimming the relief valve? Incidentally, Just before this all took place, it was difficult for the lever to stay in the detent position. Sometimes it did, sometimes it didn't. Until then, all was well. I fiddled with the detent control and got it to hold position. All was clean in there, too.

J_J · Nov 10, 2013

I am not even sure you can squeeze a hyd hose. Most times you feel the hose for pulses or vibrations.

If your valve is spring center to neutral, do you have equal spool movement when you push or pull the lever for flow, and you did say that the spool is complete and tight.

The relief valves purpose is to relieve pressure but there has to be some flow. If the work port has no flow, how can the relief valve relieve anything.

Where is the flow to make relief pressure.

If the pump is pumping there will be flow and it has to go somewhere, and if it is not flowing out through the work ports .

You might look at the load check valve for debris and or broke spring.

Did you switch hoses or QD's lately.

Lastly, check the coupling between the engine and pump. You may just have sheared the shaft key on one of the couplers.

To see if the pump is pumping the correct GPM's, remove the In hose on the log splitter valve and place in a bucket and time the flow.

If that looks good, reconnect the hose and remove the OUT hose to the filter and place in a bucket and opearate the log splitter and max out the cyl and see if the pump is still pumping the correct GPM flow.

mrcaptainbob · Nov 10, 2013

Thanks for the suggestion on checking pump flow, J-J. I just may do that. So far you all hit the mark. I managed to extricate the pump from the splitter. (This is a 'borrowed' unit. Breaks on my time, it's my dime...that's how I see it.) Had to use a puller to remove the Lovejoy type coupler from the pump shaft. It's aluminum and the set screw would not budge. The pump shaft is buggered up. Not sure what went on with it in the past, but it appears the coupler was sleeved. Removed the remains of the key from that and cleaned it up. The plan is to drill/tap for a new set screw. (One with plenty of Never-Seize!) Next is to Dremel a new key way in the pump shaft. The fit between the coupler and shaft is still pretty sound.
Thank you all so much for helping me and prompting me to investigate that pump shaft area. It was very well hidden behind some castings.

mrcaptainbob · Nov 14, 2013

Rats. That was not it! Although the key was split and the shaft ws in poor shape, I did manage to recover the situation. New key way, new key and two set screws later and...well, it's all the same. I guess I will be investing in a high pressure gauge to verify output of pump and cylinder pressures. As an aside....the unit was low on fluid. I replenished using hitrans, the stuff for hydraulics/transmissions. Would that cause issues? Should I drain it out and use straight hydraulic fluid?

J_J · Nov 14, 2013

Whatever the pump flow is, if you direct the flow into a bucket, do you have the advertise pump flow .

If the return filter new or clean?

If you have no flow, you can't check relief pressure.

The detent part of the log splitter is for the return stroke. Do you have cyl extension and can it go into relief?

oldnslo · Nov 14, 2013

J_J said:
Whatever the pump flow is, if you direct the flow into a bucket, do you have the advertise pump flow .

A word of caution on measuring pump flow in this manner on log splitters. Typically the reservoir on a log splitter is equal to or less than the rated no load pump flow so that in less than one minute the reservoir is empty.

J_J · Nov 14, 2013

That is true, however,

One gallon pumped in 6 sec = 10 GPM

mrcaptainbob · Nov 14, 2013

There is no return filter. The first thing that happened to this unit was when the hose from the ram end to the valve blew. The wire wrap was exposed in places and was rusted. I replaced that. The splitter worked fine after I cycled the air out of it. Did about a truck load of easy-to-split oak. Then it quit working. No pressure to split anything. It enters a six by six and presses the wood about an 1/8" onto a really sharp blade. The return will hold the detent position, but will not kick off when the travel is complete. The rpm's drop by maybe 25 or 50. Hardly noticeable. The cylinder does move slow, but, even though there'd be a restriction someplace, would not pressure still build? Since it was seemingly instant when it happened, could that be from a pump not pumping? I believe it is a van pump. Is it possible the vanes are stuck in position? Maybe I should pull that and check it out? I look in the tank and can see oil movement at three positions. Fore/aft/centered. The detent and relief springs are not broken.

wdchyd · Nov 14, 2013

Just pulling stuff apart is not a good idea.....you'll end up with multiple problems

You need someone with a flow load/meter to rule out pump flow and pressure before disassembling any components....otherwise you will just be spinning your wheels and digging in deeper

Egon · Nov 15, 2013

As mentioned disconnect the discharge hose before the control valve and check for flow. After you get flow start looking at the splitter control valve.

oldnslo · Nov 15, 2013

wdchyd said:
Just pulling stuff apart is not a good idea.....you'll end up with multiple problems

You need someone with a flow load/meter to rule out pump flow and pressure before disassembling any components....otherwise you will just be spinning your wheels and digging in deeper

Very good advice given here. The flow load/meter will give you the best information. A damaged pump will produce flow at no load so just looking at flow from a hose under no load doesn't tell you much.

mrcaptainbob · Nov 15, 2013

YIKES! I looked into 'acquiring' a flow/load meter, but I'd be better off just getting a new splitter for the price of some of these!! I'll do two things. One is to check the flow rate as J-J suggested. The next is to get a pressure gauge and find what the pump is producing....or can produce. There is a tag on the pump that says how many gallons per revolution is produced. I bet I can manually give it twenty or so revs and multiply it out for a close-enough flow. Frankly, it appears more of a pressure issue than flow, but I'm trying my best to follow the suggestions of my expert friends here (relative to the finances....).

J_J · Nov 15, 2013

mrcaptainbob ,

With out having to spend a lot of money, to check a hyd pump, you can put a relief valve in the pump circuit and use a needle valve and a hyd gage to put some resistance on the pump. Put the hose in the reservoir for the expended fluid..

Set the relief valve about 2000 psi, start engine and slowly turn down the needle valve. If the pump is working good, it will build up pressure as you turn in the needle valve, and if it starts relieving at 2000 psi, then you can assume the pump is working up to that pressure.

If you can not build up the relief pressure, then the pump is bypassing and needs some work or replacing.

A good hyd shop can also test your pump for shop labor, about $45 to $75.

mrcaptainbob · Nov 15, 2013

Two great suggestions. Thanks, J-J.

oldnslo · Nov 18, 2013

captain bob,
Do you have a brand name or model or both for this pump. You stated that you think it is a vane pump.

Does the oil movement in the reservoir continue when the cylinder has stopped moving and the directional valve is held in the shifted position?

mrcaptainbob · Nov 18, 2013

It's a Republic pump. Not sure of the first character, I think the info is:
Model: 0212 3S2 AB
RPM: 2000
PSI: 2200
cu "/rev: .364
It appears there is oil movement in all positions. I presume I could verify by removing the line to the tank in port.
Frankly, I was VERY surprised to see the pump shaft had been damaged at least twice before. I'm sure that shaft originally had but one key way. It got buggered up, then a new one was cut. And that was buggered up too! And...the key was sheared. So I cut yet a new key way and made up a new 'key' for it. And since the old set screw could not be removed, I drilled/tapped for two 1/4-20's at the 120* positions from the key slot on the coupler. It's nice and snug now. I am astonished that the pump would meet such a load so as to rip that key through the shaft! I would have thought something else in that pump or hydraulic line would have gone first.