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Genie RT 2668 - Slow/Barely lifts

Joined
May 14, 2020
Messages
13
Location
Oregon
Hey everyone,

I have a Genie RT 2668 - hours somewhere in the 3500 range. Since owning it, the only issue I had was when a wire frayed between the upper and lower controls. However, between uses (about a week in between), it suddenly no longer lifts, or will lift very, very slowly if the controls from the ground are used.

I threw a gauge on the test ports on the valve block and got readings of 1,000 - 1,600 psi while trying to lift. I did not yet chock the tires and try to test the pressure while driving forward. I then took out the relief valve for the lift circuit and it appears to be fine visually.. I disassembled, cleaned, and reassembled it. No change. I then swapped it with one of the 'system' relief valves, and still no change. After that, I put together a couple gauge setups and hooked them up to the 2 outlets on the hydraulic pump. It would only crank for a couple of seconds since it was fighting the pressure, but both gauges bounced off of the 3,500 psi range.

Any ideas? I'm unsure if maybe one of the other 'system' relief valves could also be affecting the lift circuit somehow? It seems like if the pump was bad, I'd be getting bad readings directly off of it, and the other functions (driving, steering) wouldn't work. It also seems like if it were the cylinder seals on the ram, there would be some fluid release and I'd be getting proper readings off of the test ports. Oh, I also replaced the hydraulic oil filter.

Any help is greatly appreciated.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
there is usually a relief valve for each spool body.

Another is probably open.

You should have around 3000 psi at lift circuit.
 
Joined
May 14, 2020
Messages
13
Location
Oregon
As in the two system relief valves would also affect the lift circuit? I was under the impression that the circuits were isolated in the valve block. I'll pull those and clean them as well.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
I don't know your machine at all.

But with my Lull one spool block controls the boom functions has a Husco relief valve.

The next separate spool valve blocks control the frame and fork tilt and it has a Gresen relief valve.

After replacing my main pump my my hydraulics were very weak and no frame tilt due to that Gresen valve being stuck open so yes they all relief valves work in sync.
 
Joined
May 14, 2020
Messages
13
Location
Oregon
So, I got a new relief valve and swapped a few around... I'm now getting proper pressure on both test ports for driving forward, but no matter which one I have in the relief valve spot, I'm only getting 1100 psi or so instead of the 3,000+ I should be seeing.

Is it possible that the coil/solenoid for the lift circuit isn't functioning correctly?

I did notice that when removing the lift relief valve, oil just pours out. However, for the steering relief valve, only a little came out, as if the circuit is blocked while the machine is off.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
In the Lull procedure for adjusting the Husco and Gresen valves it stated adjust the Husco first check pressure and adjust.

Then proceed to the Gresen adjust that.

What I found was I needed to adjust both at the same time to get everything correct.

And yes after I had all the pressures correct I still had no fork tilt up or down. I verified pilot pressure 500 psi to both so that left the spool sticking in valve which it was cleaned it brake clean now forks work.

You can do the same verify getting 12v dc voltage to spool with a power probe or whatever or apply power if so and nothing works your spool piston in valve may be stuck or bad seals.

Concerning the now flow when u take the relief out idk but that wouldn't be a major concern to me.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
So, I got a new relief valve and swapped a few around... I'm now getting proper pressure on both test ports for driving forward, but no matter which one I have in the relief valve spot, I'm only getting 1100 psi or so instead of the 3,000+ I should be seeing.

Is it possible that the coil/solenoid for the lift circuit isn't functioning correctly?

I did notice that when removing the lift relief valve, oil just pours out. However, for the steering relief valve, only a little came out, as if the circuit is blocked while the machine is off.
One other thing to check is on my lull frame tilt not working I verified the proximity switch sending power to lockout hydraulic valve in system to allow flow to tilt cylinders on frame.


If you have any lockout safety valves on your circuit that's not working check they are allowing flow.
 
Joined
May 14, 2020
Messages
13
Location
Oregon
Hmm, I guess maybe I can get a couple more new relief valves and replace them as well. Just seems weird as it was working a few weeks ago, so I'm thinking something must have 'happened', so to speak.

I'll throw the multimeter on the solenoid coil and see what I get for voltage. I checked resistance for the coil itself and it's all good at the spec'd 5 ohms. Maybe try a jumper wire from the battery or ecu. It's a 10v solenoid coil so I don't want to fry it. It has diode protection so I guess that could have failed but still show 5 ohms.

No lockout valves.. The 'down' valve seems to be working properly. If I do raise the platform very slowly, it has no problem holding. The ram is a 1 way ram, so no issues of flow through it, and connections all look good. The lift circuit is the only circuit in the valve body having issues and not showing proper pressure at the relief valve, so I was just thinking that maybe the oil pouring out was an indicator that the solenoid isn't working properly? It's a 2 position 4 way solenoid - I'm not entirely sure how it functions in the context of this machine. I did pull the solenoid itself and all of the o-rings and everything else looked good visually.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
Hmm, I guess maybe I can get a couple more new relief valves and replace them as well. Just seems weird as it was working a few weeks ago, so I'm thinking something must have 'happened', so to speak.

I'll throw the multimeter on the solenoid coil and see what I get for voltage. I checked resistance for the coil itself and it's all good at the spec'd 5 ohms. Maybe try a jumper wire from the battery or ecu. It's a 10v solenoid coil so I don't want to fry it. It has diode protection so I guess that could have failed but still show 5 ohms.

No lockout valves.. The 'down' valve seems to be working properly. If I do raise the platform very slowly, it has no problem holding. The ram is a 1 way ram, so no issues of flow through it, and connections all look good. The lift circuit is the only circuit in the valve body having issues and not showing proper pressure at the relief valve, so I was just thinking that maybe the oil pouring out was an indicator that the solenoid isn't working properly? It's a 2 position 4 way solenoid - I'm not entirely sure how it functions in the context of this machine. I did pull the solenoid itself and all of the o-rings and everything else looked good visually.
I wouldn't buy any relief valves just check if they are plugged and stuck open.

They usually never go bad.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
Hmm, I guess maybe I can get a couple more new relief valves and replace them as well. Just seems weird as it was working a few weeks ago, so I'm thinking something must have 'happened', so to speak.

I'll throw the multimeter on the solenoid coil and see what I get for voltage. I checked resistance for the coil itself and it's all good at the spec'd 5 ohms. Maybe try a jumper wire from the battery or ecu. It's a 10v solenoid coil so I don't want to fry it. It has diode protection so I guess that could have failed but still show 5 ohms.

No lockout valves.. The 'down' valve seems to be working properly. If I do raise the platform very slowly, it has no problem holding. The ram is a 1 way ram, so no issues of flow through it, and connections all look good. The lift circuit is the only circuit in the valve body having issues and not showing proper pressure at the relief valve, so I was just thinking that maybe the oil pouring out was an indicator that the solenoid isn't working properly? It's a 2 position 4 way solenoid - I'm not entirely sure how it functions in the context of this machine. I did pull the solenoid itself and all of the o-rings and everything else looked good visually.
Ok I would just check to see if the coil is getting power when u activate the function.

if you can get a T test fitting check the hydraulic pressures on the out let of the direction valve.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
Hmm, I guess maybe I can get a couple more new relief valves and replace them as well. Just seems weird as it was working a few weeks ago, so I'm thinking something must have 'happened', so to speak.

I'll throw the multimeter on the solenoid coil and see what I get for voltage. I checked resistance for the coil itself and it's all good at the spec'd 5 ohms. Maybe try a jumper wire from the battery or ecu. It's a 10v solenoid coil so I don't want to fry it. It has diode protection so I guess that could have failed but still show 5 ohms.

No lockout valves.. The 'down' valve seems to be working properly. If I do raise the platform very slowly, it has no problem holding. The ram is a 1 way ram, so no issues of flow through it, and connections all look good. The lift circuit is the only circuit in the valve body having issues and not showing proper pressure at the relief valve, so I was just thinking that maybe the oil pouring out was an indicator that the solenoid isn't working properly? It's a 2 position 4 way solenoid - I'm not entirely sure how it functions in the context of this machine. I did pull the solenoid itself and all of the o-rings and everything else looked good visually.
You pulled the direction valve coils off as well as the spool connectors and checked the piston ? Sometimes a O ring from the spool can get loose and jam it.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
Hmm, I guess maybe I can get a couple more new relief valves and replace them as well. Just seems weird as it was working a few weeks ago, so I'm thinking something must have 'happened', so to speak.

I'll throw the multimeter on the solenoid coil and see what I get for voltage. I checked resistance for the coil itself and it's all good at the spec'd 5 ohms. Maybe try a jumper wire from the battery or ecu. It's a 10v solenoid coil so I don't want to fry it. It has diode protection so I guess that could have failed but still show 5 ohms.

No lockout valves.. The 'down' valve seems to be working properly. If I do raise the platform very slowly, it has no problem holding. The ram is a 1 way ram, so no issues of flow through it, and connections all look good. The lift circuit is the only circuit in the valve body having issues and not showing proper pressure at the relief valve, so I was just thinking that maybe the oil pouring out was an indicator that the solenoid isn't working properly? It's a 2 position 4 way solenoid - I'm not entirely sure how it functions in the context of this machine. I did pull the solenoid itself and all of the o-rings and everything else looked good visually.
If it's a low voltage coil 10v I wouldn't connect any direct power from a battery.

With a Power probe you can apply safe 12VDC to circuits direct and it has a breaker so if they arc shorted etc won't melt wires etc.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
Ok I see this is a scissor lift machine it's probably very simple compared to the Telehandler I have.

Your frayed wire may have damaged shorted the direction valve coil circuit I would focus on that.

I wouldn't be replacing relief valves etc.
 
Joined
May 14, 2020
Messages
13
Location
Oregon
How would I tell if they're stuck open? Here's an example of one (https://www.gciron.com/52376GT_VALVE_RELIEF_3500PSI_Genie_Parts_p/52376gt.htm). It has ports in the end and the internal hex socket adjusts the pressure of the spring against the end piece - not sure what it's called. But the o-rings and the ports all look fine.

The solenoid inserts into the valve block, so the only way I can test the pressure is using the test port while trying the lift function and I'm getting around 1100 psi vs the 3,000+ it should be. Seems like it's not the relief valve so the solenoid seems possible... I did pull the actual solenoid from the block and all of the o rings and ports looked fine.

I'll see if I can test the voltage where the wire exits the ecu and if it's 10v there but not at the solenoid, I'll jump it and see if it functions.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
How would I tell if they're stuck open? Here's an example of one (https://www.gciron.com/52376GT_VALVE_RELIEF_3500PSI_Genie_Parts_p/52376gt.htm). It has ports in the end and the internal hex socket adjusts the pressure of the spring against the end piece - not sure what it's called. But the o-rings and the ports all look fine.

The solenoid inserts into the valve block, so the only way I can test the pressure is using the test port while trying the lift function and I'm getting around 1100 psi vs the 3,000+ it should be. Seems like it's not the relief valve so the solenoid seems possible... I did pull the actual solenoid from the block and all of the o rings and ports looked fine.

I'll see if I can test the voltage where the wire exits the ecu and if it's 10v there but not at the solenoid, I'll jump it and see if it functions.
You can usually take them apart.

On some you can insert a hex wrench or similar in the bottom port and it will compress back and forth.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
Here was mine with pump seal plastic debris in it.
 

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Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
How would I tell if they're stuck open? Here's an example of one (https://www.gciron.com/52376GT_VALVE_RELIEF_3500PSI_Genie_Parts_p/52376gt.htm). It has ports in the end and the internal hex socket adjusts the pressure of the spring against the end piece - not sure what it's called. But the o-rings and the ports all look fine.

The solenoid inserts into the valve block, so the only way I can test the pressure is using the test port while trying the lift function and I'm getting around 1100 psi vs the 3,000+ it should be. Seems like it's not the relief valve so the solenoid seems possible... I did pull the actual solenoid from the block and all of the o rings and ports looked fine.

I'll see if I can test the voltage where the wire exits the ecu and if it's 10v there but not at the solenoid, I'll jump it and see if it functions.
Yeah you gotta trace that circuit determine why it's only getting 1100 psi.

If you have damaged wires etc it may not be getting full 10v to open the valve all the way for example.
 

Roadoil

Well-Known Member
Joined
Sep 6, 2022
Messages
164
Location
Vegas
That hex cap on the relief valve removes so you can adjust pressure

I think you have a wiring issue from short not getting full voltage to direction valve.

You can swap another coil to try it on that one to test also if coil got damaged.
 

skata

Senior Member
Joined
May 10, 2007
Messages
1,541
Location
midwest
In my experience it's usually wiring issue. Did you read the service manuals? Genie had a procedure to reroute one or two of the solenoid ground wires to the battery. Do you currently have any small wires going to ground on battery? Check the condition of those.
 
Joined
May 14, 2020
Messages
13
Location
Oregon
There is the main ground and then two other large-ish gauge grounds on the battery. I did read through the service manual, parts manual, etc.

So, I think I solved it, but haven't had time to fully test.

I actuated the throttle further while lifting and it seemed to work properly. I hadn't tested the idle speeds. Investigating further, the spring connected to the high idle control solenoid has stretched out, and the arm that the spring connects to has slowly worn close to 1/4", with both of these resulting in a lower idle speed than it should be at. I'll drill a new hole and adjust the jamb nut and arm in to compensate for the stretched spring and see what happens.

Thanks for the help everyone.
 
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