FLHayman
Bronze Member
I have an old JLG boom lift, 40F, that had one bank of propo controls, one bank of regular directional solenoids. The Racine proportional controls had many issues when I bought it, couldn't get anyone to fix it, so I replaced the 4 valve bank with a generic set of Hyvair 12v D5 4 way valves. They are not proportional, so I put an adjustable dual direction restrictor valve on one side of the boom swing motor, to prevent big movements. The valve going to the drive motors has port A and B normally tied together,type F, in case the motor tried to freewheel to a stop (hydraulicly released brakes normally stop it instantly).
The hydraulic filter is now a generic return line filter sized for 25gpm, I think, returning to the tank. Originally, it had a high pressure filter going to the propo valves, but no element in it! I put a new relief valve on the new bank of valves turned up slightly from 1500 psi. Anyway, this set up was working fine, and I noticed over a few hours of use that I would have to blip a function from the OTHER bank in order to get the main boom holding valves to allow the boom to go up or down. When this happens, you can hear the valve for the boom shift, the relief goes into bypass, and nothing further will happen until I momentarily blip something like the platform level or the telescope function.......then the boom moves with absolutely no problem, up or down, no strain on the motor, even at idling speed. I thought it must be the holding valves, which are hard to get to, and require lifting up the boom to access, with associated peril.......then the boom swing function started doing the same thing.
I haven't got a gauge mounted, but used one to test it, and all was well, initially. The rat's nest of hoses that I've put everywhere precludes easy access to the return filter, but changing that is on my list of things to try. After reading a lot of info here on the forum, I'm wondering if my choice of valve manifold or valves may be causing this problem. I used a parallel bored aluminum D5 block to hold the 4 valves. The 2 functions that are getting the cylinder holding valves stuck are Hyvair type B 4way valves. I'm sure the valves are working right and are happy with the current. I am finding it hard to believe that all the holding valves are bad, then suddenly work when I momentarily hit the controls on the other bank of controls. The kicker is that the other bank of controls is plumbed to a separate section of the 3 section pump, and has it's own dump valve. It returns through a Y to the tank.
OK, I don't know the plumbing of the old Racine valves, nobody else around here could help me with that, but I do know that it seems to be a closed center design, with the flow from the pump/bank in question going straight to a dump valve, normally dumping back to tank. All the dump valves have more than one thing Y'd to them on the way to the tank, such as case drains.
Some specific questions: Would it matter if my valves were normally connected pressure to tank, since the dump valve only pressurizes the block when energized along with a valve command?
If I energized the dump valve slightly before, or slightly behind the valve command, would it solve this problem of the holding valves not letting up easily? (at the moment, they are on double pole switches and theoritically actuate at the same time).
I am trying to get ideas for troubleshooting when I get home from this long business trip, and hope that someone with experience at holding valve anomolies could help. Thanks!
The hydraulic filter is now a generic return line filter sized for 25gpm, I think, returning to the tank. Originally, it had a high pressure filter going to the propo valves, but no element in it! I put a new relief valve on the new bank of valves turned up slightly from 1500 psi. Anyway, this set up was working fine, and I noticed over a few hours of use that I would have to blip a function from the OTHER bank in order to get the main boom holding valves to allow the boom to go up or down. When this happens, you can hear the valve for the boom shift, the relief goes into bypass, and nothing further will happen until I momentarily blip something like the platform level or the telescope function.......then the boom moves with absolutely no problem, up or down, no strain on the motor, even at idling speed. I thought it must be the holding valves, which are hard to get to, and require lifting up the boom to access, with associated peril.......then the boom swing function started doing the same thing.
I haven't got a gauge mounted, but used one to test it, and all was well, initially. The rat's nest of hoses that I've put everywhere precludes easy access to the return filter, but changing that is on my list of things to try. After reading a lot of info here on the forum, I'm wondering if my choice of valve manifold or valves may be causing this problem. I used a parallel bored aluminum D5 block to hold the 4 valves. The 2 functions that are getting the cylinder holding valves stuck are Hyvair type B 4way valves. I'm sure the valves are working right and are happy with the current. I am finding it hard to believe that all the holding valves are bad, then suddenly work when I momentarily hit the controls on the other bank of controls. The kicker is that the other bank of controls is plumbed to a separate section of the 3 section pump, and has it's own dump valve. It returns through a Y to the tank.
OK, I don't know the plumbing of the old Racine valves, nobody else around here could help me with that, but I do know that it seems to be a closed center design, with the flow from the pump/bank in question going straight to a dump valve, normally dumping back to tank. All the dump valves have more than one thing Y'd to them on the way to the tank, such as case drains.
Some specific questions: Would it matter if my valves were normally connected pressure to tank, since the dump valve only pressurizes the block when energized along with a valve command?
If I energized the dump valve slightly before, or slightly behind the valve command, would it solve this problem of the holding valves not letting up easily? (at the moment, they are on double pole switches and theoritically actuate at the same time).
I am trying to get ideas for troubleshooting when I get home from this long business trip, and hope that someone with experience at holding valve anomolies could help. Thanks!
