hydraulic power / loader

[mickd]

I recently bought a ford 1700 with a770 loader. I'm still changing oils, re packing cyllinders etc. before I haul it to our camp .
I notice that the loader will not pick front tires off the ground ----- ? should it be able to ? If so where should I start looking for the problem . Thanks Mick

 

[jinman]

Mick, how did you go about trying to lift the front? If you had the bucket flat and tried to use the lift arms only, you might not get the front into the air. You either have to put the bucket flat on the ground and then curl it to the dump position or put it in the dump position and the lower the lift arms. If that is what you did, then you might have weak hydraulics and you probably need to invest in a 3000 psi gage hooked to a quick-connect adapter so you can put it into the loader hydraulics and measure the pressure. If your loader won't lift, you need to identify whether the problem is the pressure or maybe an internal cylinder leak. The pressure gage will really help with that. Also, if you lift your loader with the bucket flat and then turn off the engine, does the bucket sag? Arms drop? Either of these could mean you still have an internally leaking cylinder or your joystick valve is bypassing. When you center your joystick, you remove the pressure relief valve from the circuit, so any leak-down is probably internal cylinder leakage.

 

[mickd]

I was working the lift and bucket cyllinders full in and full out after replacing the packing in the bucket cyllinders, then turned the
bucket (cutting edge down ) and tried to raise the front end by the loader arms- not enough down force to pick it up. Before trying to raise the tires off the ground, I did cycle all functions numerous times in hopes of getting any trapped air out of the system

 

[mickd]

Jim , when I get home ,I'll try lifting the machine by dumping the bucket,(those cylls just re packed ) . If that picks up the tires , should that mean the hyd. pressure is ok ? I will also shut it down with the loader off the ground and see if it holds or settles, as you suggest. I would hope not to have to get into a hydraulic pump, the cyllinder re packing was'nt so bad. I'll let you know tomorrow how it went Thanks.

 

[jinman]

Mick, picking up the front really is only a quick way to verify that your loader can do some real work. It doesn't guarantee anything about maximum loader efficiency or power/pressure. On an older tractor, I'd suspect you might not have full pressure from your pump, but if you force the loader arms down as far as they go, you should be able to hear the system relief valve lift if you have good hearing. If the system relief valve is lifting, most likely you have normal pressure unless the relief valve spring is fatigued from old age or somebody has removed shims. On your 1700 model tractor, you may have a separate relief valve in the 3PH circuit and one in the supply for the FEL. The one for the FEL should be in a block on the right side of your tractor just in front of the foot rest. On later model 1700 series, this is the location of the relief valve.

 

[mickd]

Jim, the pic you sent does,nt look familiar, mine is an 80, and fluid is fed to the controls from 2 hoses originating under the right side of the seat, I'll look for the relief valve and listen though. I just got the tractor ,seems to have been pretty well taken care of, previous owner passed 10 or 11 years ago and it sat in a garage til now. Only shows 550 hrs on the meter so I hope its a minor fix. I'll let you know

 

[J_J]

What Jinman said plus.

Yep, get your self a 3000 psi hyd gage with a QD on it to allow you to plug it in wherever. Your best position for the gage is up by the control levers where you can see it to monitor and trouble shoot the hyd system. Add a tee with a QD at the IN port of the loader valve . Plug your gage in the QD.

What it can tell you is this. With no hyd lever engaged, you should see no or very little pressure as the fluid is just flowing through all the hyd valves.

You will see relief pressure if you max out the cyl, in retract or extend.

If you raise the 3pt to max, you will see relief pressure for the 3pt.

As you raise a load, you will see what pressure the lift cyl's are developing.

You can also check and set your relief pressure for any relief valve.

Just lifting the wheels off the ground might only take about 1000 psi, and might not reflect the max pressure or load the tractor is capable of.

If your pump and cyl can develop the factory stated relief pressure then you have a base line to work from.

 

[mickd]

JJ, I was hoping for the easy fix, for me that would be re packing the lift cyllinders ,then all 4 would be gone over. Is the test gage a specialty tool I'm going to have a hard time finding ? Is it expensive ?

 

[J_J]

No, the test set would cost no more than $30.

Can find at any TSC

Surplus Center

A tee that will fit your hose and screw into the IN port of the loader valve, and a QD

 

[wdchyd]

Mickd,

Correct me if I'm wrong but those lift and bucket curl cyls have each a single set of v-packings for the piston seals....Yes/no..??.... Hercules Sealing Products-Hydraulic cylinder repair seals and seal kits, replacement cylinders and cylinder components for construction and many other heavy equipment industries.

the lift cylinder v-packing set is positioned so the main function will be doing lifting (push out).....and the bucket curl v-pkg set is positioned so the main function will be doing pulling.....(to hold the full bucket of dirt)

Did you happen to notice how these were different when you took them apart, they should be

770-SERIES FORD LOADER (1/79-12/83)

Even though all four cyls are ported for double-acting usage, their main function was intended for one way under full pressure......not the other

To sum it up, trying to lift the front end is not a good way to test cuz the lift cylinders will slightly by-pass while using them for pull (lifting off the ground) and are not pressure tight in that direction

Also the v-pkgs sets are very sensitive to having the right "tension" when they go back together (not too tight and not too loose).....You should feel a healthy snug fit with a light plastic hammer