No cylindder pressure....

[wdchyd]

Recommend you take the pump to a hyd shop for testing.

They're gonna need the whole splitter, easier to put flow/meter inline than to mount the pump on a test stand (which most repair shops do not have)

 

[J_J]

What is the HP on your log splitter engine?

Is this a factory or home made splitter?

 

[mrcaptainbob]

It's a home made splitter, J-J. And, from what I understand, the neighbor that owns (now deceased...) is/was the third owner and has had it for about six years. A month or so ago it needed a head gasket. I was told it was a ten horse Briggs. Glad I brought the old gasket for a match up, as it turned out to be a Tecumseh! It still may be a ten horse, though!

 

[mrcaptainbob]

Moved the cylinder to center and checked for any internal bypass. It's good. The pump is now on the bench with both ends off. Under the inlet end there were six balls, each covered by a light duty spring. Nothing broken there. No obvious signs of pitting. The ports the balls lay in appear to be screw inserts. The casting is lightly punched two sides at each insert. Each insert has two large slots assume are used for unscrewing. On the mounting end there's a seal in that casting. Removing it and there was a shim on a ball bearing. That's as far as I got before I start damaging stuff. My question is how to remove the shaft and bearing. There is a center hole at the inlet end of the pump where it appears I could punch the shaft. But only if it has a shoulder that the ball bearing at the other end rests on. Looking for guidance on this. Once the bearing comes out, what guts should I expect? Lots of small spring loaded bearings? Fins? Should I lightly tap the far end of that shaft?

 

[mrcaptainbob]

Took the pump apart. It's a piston with swash plate type. The six pistons are very smooth in the cylinders with absolutely no side movement. I mic'd the polished used part with the unused surfaces and there is no difference in diameters. The springs are all equal length. Nothing seems out of sorts. Except....at the port end there are two 'O' rings. One around the input port and the other at the casting perimeter. Both seem to be less than 'supple'. And flat. Could it be that pressure was leaking past a weak seal? I presume it should be an 'O' cross section and fits in a square slot. I'll take the end plate and 'O' rings to a local hydraulics shop and maybe they can match them up. Anxious to see if this solves the problem....

 

[oldnslo]

Captain,
On the six balls, do some of them connect to the suction or inlet port and the others to the pressure port or are they all common to one port? It almost sounds like you are describing a check ball style pump.

If this link works it is an example of a Dynex check ball pump.
High Pressure Pumps for Hydraulic Systems

 

[mrcaptainbob]

That's it, Oldnslo. Except the intake is on center on the end and is sucked in through the sidewalls of the cylinders similar to a two cycle. But it compresses and does eject through the check balls at the end of the cylinder. Since it would allow oil to drain from the tank through the pressure port, I assume it can only mean that either the center seal is allowing bypass or the check ball springs need replacing. Come Monday I will try to scare up new seals and try for new springs, too.

 

[oldnslo]

Captain,
In theory the pressure should seat the check balls. I have limited working knowledge on this style pump so i would only be guessing on what would cause it fail. Possible only one or two of the pistons are pumping properly which would allow pressure buildup with the needle valve but add any leakage from a spool valve and it may all be lost.

Best of luck on the rebuild.

 

[mrcaptainbob]

Eureka!! I purchased the two 'O' rings and found that they should be circular in cross section and not square. But while reassembling it I found two of the six check ball springs to be shorter than the others by two coils! While the 'good' ones were flat and tapered at the spring ends, these two were obviously cracked off, as the wire was flat at it's tip. Easy to see comparing the two ends. It does appear that this would allow for the slow but constant dripping of the reservoir through the pump, and would also point to the low pump pressure. And may also point to the high reading when using that gate valve. High pressure, but low volume. So, I need to get six new ones. Six springs with six coils at .025 wire diameter x .40 high x .30 diameter. Where can I get stuff like that? Would a hydraulic shop sell me something like that?

 

[oldnslo]

A good hard ware store may have some or possibly McMaster Carr. I doubt a hydraulic shop would have them but possible.

 

[mrcaptainbob]

After contacting the company, I was sent to a spring manufacturer. The original springs are .4 tall, .3 diameter, .025 wire diameter and six coils. Ordered new springs. .438 tall, .3 diameter, .024 wire diameter and 4 coils. Don't know the spring rate of the originals. I'd bet they were taller when new. As for the other differences, I'm thinking the smaller wire diameter would make up for the difference in number of coils. I know there's more deflection per coil. I suspect there's not much deflection when in use. Although the new springs are bought and paid for and are on their way, I still would like your opinions.....

 

[oldnslo]

Capt,
You are correct in that these springs should defect very little. The actual amount will vary to some degree with pressure. Low pressure they will deflect a little more than at high pressure.

 

[mrcaptainbob]

Okay, so it's back together and...IT WORKS!! EUREKA!! However....(I sure hate when people say that....) after exercising the cylinder as best as I could, it goes real, real slllloooww.... But it does build pressure. Okay, so it was 19* when I did it. I'm thinkin' the oil won't pump to well at that temp. Saturday is going to 40*, so I'll try it again then. As an aside, I did hold the valve to close the cylinder past detent and it rattled fierce and climbed well past 1,000 psi. Okay, good sign there. And after fully extending it it seemed thqt it finally would climb to higher pressures. When I placed a log in to split, it popped it at around 700- 800 psi. I was surprised at the low pressure to split it! Okay, big cherry log time. Now it climbed to nine hundred and the cherry popped apart. Yeah, it was all frozen. So I shut it down until warmer weather. Anxious to find out how it acts in warmer weather.

 

[oldnslo]

Capt,
I believe that one of the flaws of the check ball style pump is that they have a very poor inlet vacuum capabilities. Running them while cavitating is a death sentence to the pump.

 

[mrcaptainbob]

Ahhh....so you're sayin' that those pistons can't pull the thicker-er oil they need. Never thought of that. It seems the oil would be thin enough, even at gravity feed, to flow through a one inch supply hose. Although the pump has a half inch inlet. And those casting ports for those little, dinko pistons aren't very large. Yeah....I can see that now. The pistons are gulping for stuff that has a hard time flowing. Thanks for opening my eyes some more. It was in the mid-30's today. It did seem to run much better, the cycle time was much improved, and by the time I finished, which was about two hours later, it seemed to build pressure a bit quicker.
I used the same hydraulic oil bucket to top off the tractor transaxle today. I was surprised to hear a 'thunk' while I poured to the funnel. Found there was .... A BLOCK OF ICE IN IT!! What the hey??? I left it outside by the splitter a few weeks back. But it was capped off, and that tub neck was extended. And it was under the same tarp as the splitter. DANG it! So now I'm thinkin' I just may have added some water along with the oil to that splitter and that may be why it takes a while to build pressure. I guess I have to now drain that tank and replace it. But how would I evacuate all the hoses and the cylinder from old compromised stuff? IF that's what it is?

 

[oldnslo]

What was the temperature when you filled the splitter with oil? If it was cold enough for any water to be ice I doubt you added any water to your splitter. The fact that it appears to be running faster when warm would indicate your pump is potentially still cavitating some. Does the pump growl while building pressure?

I would suggest another call to the company and ask them if they have the recommended fluid viscosity / type for this pump.

Swapping fluid: Run the cylinder to end of stroke in either direction. Drain and fill the reservoir with new fluid. Remove the line from the end of the cylinder that is full of old fluid. Place this line in a bucket. Start the splitter and activate the valve to move the cylinder to force the old oil out into the bucket. Connect that line and you should have removed the majority of the old oil. Double check the reservoir level and split some wood.

 

[mrcaptainbob]

Topped off the reservoir. It needed it. Fixed the float bowl leak and no more gas dribbles. Filled the gas tank and topped off the engine oil. Started up fine and it splits quite nicely now.
Thank you all for so much help and giving me the incentive to take that pump apart. I learned a lot from this experience and your guidance.