Old 753 hydraulic issues

[.50ae]

Hello guys, so I have an old project 753 I've been fixing up and I'm now working on the hydraulic portion of the many issues. I went through and rebuilt all the cylinders on the machine so no more leaks. Problem im having now is the machine seems to have a parasitic draw. Narrowed it down to one of the auxiliary hydraulic solenoids staying on all the time even with key off. Guessing a wiring issue. Also, the hydraulics are acting weird. Boom up and down controls are backwards and not very powerful and the tilt cylinder only moves down. My question is, would a stuck auxiliary hydraulic valve cause these issues? The two LED lights work fine on the switch in the cab. Haven't been able to test the hand controls since I can't get any attachments on with the hydraulics acting all funky.

 

[KyMadMan]

Stuck Aux valve could cause this issue. Did you rebuild the control unit? If so, did you replace any parts other than seals? You can disconnect the Aux controls to check if the valve issue is caused by a bad switch in the hand controls. Disconnecting that "system" will not cause problems with your other hydraulic functions. Does the up and down on the boom work ok other than being reversed?

 

[.50ae]

Stuck Aux valve could cause this issue. Did you rebuild the control unit? If so, did you replace any parts other than seals? You can disconnect the Aux controls to check if the valve issue is caused by a bad switch in the hand controls. Disconnecting that "system" will not cause problems with your other hydraulic functions. Does the up and down on the boom work ok other than being reversed?

Figured out the parasitic draw. It was just me not knowing the key had a third position. Goes "acc-off-on-start". I was just turning the key too far.
Switched the hoses so the boom controls work the right way now but they still only move in one direction like the tilt. Boom only goes down and tilt only tilts forward. Pretty much pedals only work going forward. Rocking the pedals back, you can definitely hear load on the motor but nothing happens. I haven't rebuild the control unit. I pulled the aux spool out last night and nothing looked to be wrong with it. Moves freely. So I tried disconnecting the solenoids and it didn't really do too much. The hydraulics acted a little different but pretty much the same. Seem like they have power.

 

[KyMadMan]

Figured out the parasitic draw. It was just me not knowing the key had a third position. Goes "acc-off-on-start". I was just turning the key too far.
Switched the hoses so the boom controls work the right way now but they still only move in one direction like the tilt. Boom only goes down and tilt only tilts forward. Pretty much pedals only work going forward. Rocking the pedals back, you can definitely hear load on the motor but nothing happens. I haven't rebuild the control unit. I pulled the aux spool out last night and nothing looked to be wrong with it. Moves freely. So I tried disconnecting the solenoids and it didn't really do too much. The hydraulics acted a little different but pretty much the same. Seem like they have power.

Not sure what all you've done so far, so don't take offense. Have you checked the adjustments on the pedals? It could be that you are only opening part way and not enough to allow full flow. Also, not sure of the hydraulic filter, that could cause a flow issue. I have some info I can send you that might help. I'll see if I can send it in a message to you.

Also, I know it sounds dumb, but check your fluid level in the reservoir. I'm sure you did after your rebuild, but just to be sure.

 

[Dave the Ozzie]

I have a 763 which I'm guessing is very similar in the Hydroulics department. As KyMadMan said take no offence at any of our suggestions; when you've reinstalled the lift rams are they plumbed correctly and you've not crossed up/down hoses over where the rams are fighting each other? I'd track each line from each ram to see that they're in parallel with each other and then make sure that the lift circuit lines go to each side of the same spool valve, do the same with the tilt cylinder, that way you can eliminate the obvious first before you can move on.

 

[Markle]

You said you had a wiring issue and a stuck aux hyd magnet/solenoid. Resolve that issue first. Validate you have proper aux hydr function, both directions. stuck aux hydr solenoid could affect this problem, depending on which way the solenoid valve was stuck. Then you have the load checks and pop off valves, one for each in lift and tilt valve sections. Clean those out if suspect.

 

[Dave the Ozzie]

I have a 763 which I'm guessing is very similar in the Hydroulics department. As KyMadMan said take no offence at any of our suggestions; when you've reinstalled the lift rams are they plumbed correctly and you've not crossed up/down hoses over where the rams are fighting each other? I'd track each line from each ram to see that they're in parallel with each other and then make sure that the lift circuit lines go to each side of the same spool valve, do the same with the tilt cylinder, that way you can eliminate the obvious first before you can move on.

I just had a wild thought on top what I suggested; you do know that the system has an electric lock out circuit don't you?
Mine is a 1999 model and the safety bar needs to be down and then the traction lock override needs to be pressed before hydraulic can be activated. Mine doesn't have a pressure switch in the seat.
After going through this procedure all of the green lights should be activated on the BICS module near your right elbow against the firewall. If one is not green you'll be able see which one it is, I suspect the seat pressure switch (if equipped) or the seatbar switch, if this is the case then you can hear the hydraulics load up but will not function.

 

[.50ae]

Hey guys sorry I don't have a whole lot of time to work on this thing just an hour or two when I get it. I drove it out to an auger I have and I hooked up the aux hydraulics to it. They're definitely stuck on. Auger spins without aux being engaged. If I engage them, actuating the thumb switch will stop the auger until I let go of it then it'll start spinning again. One or both of the aux solenoids always have power when the machine is on. Guessing that's not normal. If I disconnect the aux power at the key switch it doesn't make a big difference with the operation of the hydraulics. I'll physically track the lines because the guy before me definitely had a couple switched. I think I got them right but I could be wrong. I will probably pull the hydraulic control valve out and rebuild it. It sounds to me like something is wrong/stuck inside of it.

 

[Dave the Ozzie]

Hey guys sorry I don't have a whole lot of time to work on this thing just an hour or two when I get it. I drove it out to an auger I have and I hooked up the aux hydraulics to it. They're definitely stuck on. Auger spins without aux being engaged. If I engage them, actuating the thumb switch will stop the auger until I let go of it then it'll start spinning again. One or both of the aux solenoids always have power when the machine is on. Guessing that's not normal. If I disconnect the aux power at the key switch it doesn't make a big difference with the operation of the hydraulics. I'll physically track the lines because the guy before me definitely had a couple switched. I think I got them right but I could be wrong. I will probably pull the hydraulic control valve out and rebuild it. It sounds to me like something is wrong/stuck inside of it.

There's an electrical connector on tails of all spool solenoids, figure out which is the auxiliary spool and unplug it. If the auxiliary keeps going then the issue is within the spool valve, if it stops its electrical. From memory I think it's the solenoid at the rear of the spool valve housing.

 

[.50ae]

There's an electrical connector on tails of all spool solenoids, figure out which is the auxiliary spool and unplug it. If the auxiliary keeps going then the issue is within the spool valve, if it stops its electrical. From memory I think it's the solenoid at the rear of the spool valve housing.

Oops I forgot to check that. Already pulled the machine back in the garage and started draining hydraulics to pull the valve. Machine operation doesn't change while plugged into the auger. Guessing the aux stuck on and the weird hydraulic operation are 2 separate problems. If I pull aux power from the key switch the operation of the hydraulics doesn't change too much and machine seems to run a little smoother. I'll pull the valve and reseal. Once I get it back in I'll try.

 

[fortworth-cowboy]

So you resealed your cylinder? Did you had them out? Could it be that you swapped the hoses?