Hydraulic Help

Scott Y · Nov 29, 2021

Need some guidance here if possible, I installed a totally independent hydraulic system on a tractor, I installed a 12 gallon reservoir on the back of the tractor, I installed a gear pump on the very front of the tractor, front pulley has a hub to install a splined drive shaft, the pump is rated at 12.6 gallons at 1800 rpm, there is a 1" ID line going from reservoir to the pump, there is a 3/4" ID line from the pump to the valve, valve is a 4 position, open center valve, I have no pressure what so ever, cannot even hear the typical hydraulic noise , I tried adjusting the relieve valve on hydraulic valve, made no difference, I unhooked pressure line from pump to valve bank , with tractor running, oil came out but not much for flow, I guess I need to actually measure if getting 12 GPM out of pump , does not appear that reservoir is getting any return flow, can not visually see turbulence when looking thru fill cap, needless to say I am a bit stressed out, have a lot of time and money in this project, and trying to get loader on before winter, any pointers will be very much appreciated, I will look into it some more, I am assuming something wrong with the new pump, (complete system is new) it is suppose to be a CCW rotation, maybe they sent the wrong rotation pump? Thanks

ptsg · Nov 29, 2021

Sure looks like the pump is not rotating the right way. Definitely look into that. Looking from the front, what direction does the engine spin? CW or CCW? I would expect it to turn CW looking from the front.

Either way, that's a nice clean setup you built there. Great job!

Scott Y · Nov 29, 2021

I did check rotation, but I better verify this tonight, I am pretty positive the output shaft is turning CW, so ordered a CCW pump, at this point I am hoping that is the issue, could be they sent me the wrong pump, will look into that further, Thanks for your reply, I appreciate it.

mrmikey · Nov 29, 2021

Are both ports on the pump the same size, 1" and you bushed the pressure down to 3/4". If so could you have the lines reversed? Is the tank vented? Couplings are not slipping on the shafts?
Looking at the pic, (near as I can tell), if the engine is turning CW, the suction should be on the right, (passenger) side, left side as viewed in the pic. If not, I think PTSG has the answer..........Mike

Scott Y · Nov 29, 2021

Suction is SAE 16 , (RH) I am using 1" ID hose from reservoir to the pump, Pump outlet is SAE 12 , (LH) using 3/4 hose from pump outlet to valve inlet, both coupling halves are keyed and key is in place, not sure about reservoir venting, assume cap must be, but can check, yes shaft from crank is CW and pump is CCW, tonight going to hook pressure gauge up to one of the valve outlets to verify any pressure, then will make sure reservoir is getting return flow, then will check output of pump , and post my findings, Thank You Very Much for the replies.

Seven Gables · Nov 29, 2021

Could it be the pump mfg/seller intends for that pump to go on a tractor with CCW rotation as viewed from the front of tractor ? If this is the case you need one that is CW to work. All I can think of , everything else looks right.

LD1 · Nov 29, 2021

Did you hook everything up and then add oil?

That is a LONG suction line for the pump. Might just be having a hard time taking a prime.

Id unhook the suction hose (with a clean bucket handy) and make sure the suction hose has good oil flowing TO the pump and get all the air out. Hook it back up and try again.

mrmikey · Nov 29, 2021

I just thought of something else, something that happened to me years ago.
I had made up an 1-1/2" suction line with crimped on fittings. As you make up a line obviously you have to push the barbed ends of the fittings into the hose. Unbeknownst to me, I had a piece of bad hose or else I did something wrong...somehow, and the inner liner of the hose had separated and I ended up shoving the barbed fitting in between the inner and next layer of hose. Took a few hours to figure that one out...........Mike

PILOON · Nov 29, 2021

Hydraulic pumps are great to push, but with a long suction line full of air and no oil to seal the very minor vane gaps they'd be a poor suction pump.
B4 chasing for faults I'd first off prime that suction line using a funnel.

oldnslo · Nov 29, 2021

Agree on making sure the pump is primed especially with that length of suction line.

Might be a silly question but.. is the inlet hose suction rated?

1" ID is approx 5 feet per second flow rate at 12 GPM. Typical recommended max is 4 Feet per second for suction lines. approx 9.8 GPM is 4 FPS on 1" hose. Doubt this is your problem but might be an issue if running in cold weather at full throttle.

mrmikey · Nov 29, 2021

I may have been looking at that pic wrong? If the bottom gear, driver, is turning CW then the suction should be on the left, driver side.

https://learnchannel-tv.com/wp-content/uploads/2019/03/Hydraulics-External-Gear-Pump-how-it-works.gif

LD1 · Nov 29, 2021

Looking at his pic....if the suction is the right in the pic, and the driver is bottom, it is plumbed correct. He has a suction/prime problem

mrmikey · Nov 30, 2021

Looking at his pic....if the suction is the right in the pic, and the driver is bottom, it is plumbed correct. He has a suction/prime problem

Agree, once I relooked at the pic I realized the driver was the bottom where I first thought it was the top, or at least looks like it...........Mike

ptsg · Nov 30, 2021

I really doubt it's a suction or prime issue, unless the suction line is pinched somewhere around the route from the tank to the pump or something inside is blocking the line. Specially with the tank clearly sitting above the pump, that will prime itself just by pouring fluid on the tank.

Heck, I'm running the two pumps on my backhoe 6" above the tank and surely 10 to 12" above the fluid level, using an undersized suction line with a bunch of tight 90 degrees fittings and it works just fine, no problems at all with the flow.

LouNY · Nov 30, 2021

Do you have a suction filter on the system,
or a screen in the suction line.
Filters are hard to pull through.

mrmikey · Nov 30, 2021

What kind of flow do you get if you remove the suction line from the pump? The tank being above the pump, the oil should run freely out of the line.
While you have the line off, have a look inside the pump, you should be able to see the gears to check for actual rotation and correct direction of rotation. If you can, get a small hardwood stick to make contact with the gears, see if you can rotate them (engine off obviously) to check that there is actually a keyed connection from the input shaft to the driving gear. It's not unheard of to be missing parts from even new equipment, crap happens when humans are involved.
It's an extremely simple setup, I can't really see what the problem would be, it's got to be something extremely simple that we'll all kick ourselves in the butt for not seeing it

.............Mike

Scott Y · Nov 30, 2021

Thanks For all the Great replies, I did hook everything up and then fill with oil, the suction line is suction rated , good point on filling the suction line with oil, but I believe I am past that now, last night , hooked a pressure gauge up to a remote, 0 psi, so I unhooked the inlet to the valve (outlet from the pump) put thumb over end of hose and started tractor, it did build pressure , not sure if enough, but made a mess of sprayed oil on tractor, so then unhooked return line going to the reservoir, nothing coming out, a very light dribble, so this leads me to say the pump, if the pump was working but the valve wrong or closed position, the pump would build so much pressure a line would blow or stall the tractor, tonight I am going to hook up a flow meter between pump and valve (borrow from work), and see what I get, I assume zero to very very low gpm. I am (after the fact) concerned about the length of the suction line as well, but system should still work, when I get this working, I will probably bump up the ID size of the suction hose , but later on. Facing the front of the tractor the shaft/coupler rotates CW , so I ordered a CCW pump, that has to be correct? but sure seems like it must be the pump rotation is backwards, plumbing is correct, inlet is 1" outlet is 3/4. Thanks Guys. more to come yet.

Scott Y · Nov 30, 2021

no section strainer or filter, just a return line filter. Thanks

Scott Y · Nov 30, 2021

Mike, Good points, tonight In addition to measuring flow, I will remove the suction line and see what I have for flow coming out of it, yes who knows, could be an obstruction or similar, I will also check the pump out like you stated, Good to have guys to throw some options at me, yes it is a very simple system , that should be working. Thanks Guys!