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Cat 930h 2007 lift won’t stop when engaged

Dieselham1

Member
Joined
Apr 25, 2023
Messages
8
Location
Texas
It’s like the devil takes over when engaging the lift. I begin to raise the boom and then it just keeps lifting no matter what wiggling of the joystick I do. I thought trash got in the lift valve spool so I cleaned and polished some minor scratches but this seems to be electrical…. I took the small pressure lines off at the lift valve that goes from the joystick to the valve to make sure oil was not going to the lift side of the spool when it malfunctioned and that seems right…. No oil to the valve to actuate it from the joystick when it malfunctions. It’s Like the ride control takes over and hangs wide open. Tried turning off the auto for ride control and maybe that worked a few times it malfunctioned, but now it’s constantly going straight up…. Sad to say it hasn’t had the filters changed in 3 years according to the date on the filter. I’m starting there then refilling with new hydraulic fluid
 

Dieselham1

Member
Joined
Apr 25, 2023
Messages
8
Location
Texas
Hello Nige. I do not know how to access the diagnostic codes, so Pls help me do that..

I will definitely post on my results of the service of the filters and hydraulic oil change.

Serial number is 093OHJDHC02233
 

Dieselham1

Member
Joined
Apr 25, 2023
Messages
8
Location
Texas
These are the only A codes I have…. But There are several others though. I suspect these are circuit codes that came up when I unplugged some solenoids…
 

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Nige

Senior Member
Joined
Jun 22, 2011
Messages
28,984
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G..G..G..Granville.........!! Fetch your cloth.
If those are the only ones prefixed with an "A" then they are all that is active at this time.

81-740-5. Differential lock solenoid, open circuit.
81-491-5. 3rd function extend solenoid, open circuit.
91-492-5. 3rd function retract solenoid, open circuit.

I suggest that you should at least check into the last two Codes because that could potentially affect the electro-hydraulic hoist control. I see your machine is equipped with a 3rd valve attachment.

I hope you have a multimeter because you'll need one. I'll send you a copy of the electrical schematic.
 

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Dieselham1

Member
Joined
Apr 25, 2023
Messages
8
Location
Texas
The third valve open circuit I can scratch of the list as I cut this wire to replace the pig tail then actuated it, so naturally this code would set. These solenoids are pretty fried at the wire receptacle and I could not get the pigtail to come out. I initially thought this was my lift solenoid.

Can you point me in the direction of a lift solenoid on this schematic. My eyes are not to strong. I see section 42 but that looks more like the joystick location.

The machine now is consistently lifting as soon as the motor starts. It’s strange because it raises normally them hits it’s stride then goes all the way up. When you turn off the key then sometimes it will come straight down at a medium rate. If I actuate the joystick in the down position I can ever so slightly get the lift cylinders to momentarily bump but not take over the downward drop in any way. So when it starts, the lift will go all the way up and never let up. It just keeps applying upward pressure and yiu can hear the pump straining. It’s like it has another circuit taking over. That’s why I was wondering if there was a solenoid somewhere for the lift circuit that could be afoul
 

Vetech63

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Joined
Aug 10, 2016
Messages
6,362
Location
Oklahoma
You will need to determine if this is an electrical or mechanical problem. I am not familiar with this particular machine but I have dealt with electro-hydraulic controls on others. This sounds like a mechanical problem at the moment. My guess would be that either the boom up operational solenoid has seized in the up position for some reason (possibly electrical).......or the main boom spool has locked to the upside of its stroke.

Nige is the Cat expert. Definitely follow his lead!
 

Nige

Senior Member
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Jun 22, 2011
Messages
28,984
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G..G..G..Granville.........!! Fetch your cloth.
am not familiar with this particular machine but I have dealt with electro-hydraulic controls on others. This sounds like a mechanical problem at the moment. My guess would be that either the boom up operational solenoid has seized in the up position for some reason (possibly electrical).......or the main boom spool has locked to the upside of its stroke.
That's exactly where I was headed. I just wanted to eliminate the possibility that an electronic fault was causing the solenoid to be engaged.

Now after reading the SysOp I discovered that the pilot system is 100% hydraulic. My bad, I thought it was more modern. So the first thing to do would be to disconnect and plug the lift pilot line as it comes out of the pilot valve. Can you confirm that the pilot control on your machine looks like the illustration below.

1682520153733.png
 

Dieselham1

Member
Joined
Apr 25, 2023
Messages
8
Location
Texas
I was thinking about this last night and determined to try and rule out of this system was hydraulic only for the lift and a few practical tests this morning led me to believe with some certainty it was mainly hydraulic.

Previously I had removed the lift valve out of the valve body (it’s about 8 inches long) and noticed right away it was difficulty to get it to slide in and out. I noticed some visible wear on the valve and tried to polish it so it would slide better. I used fine Emory cloth and spun the valve on a drill and got the valve looking pretty good. I tried this three times and I could get it to work then the lift would stick. Right now it worked for ten minutes by removing one spring. The goal trying to get that valve in a different spot. After that failed I put the spring back in I took out and put a shim ( a quarter) in one of the cups on the opposite side of the where I took the spring out and it works. Thinking of trying to get that valve in a different spot. I’ve got this valve body assembly on order but ot is $3000. Good heavens

Machine has 14000 hours
 

Nige

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Jun 22, 2011
Messages
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G..G..G..Granville.........!! Fetch your cloth.
Based on what you say above it's quite probable that the valve body is scored as well as the spool.
The spool should slide in and out with no more than finger pressure.
Do you have any way of looking into the bore to check the condition of the tunnel.?
 

Dieselham1

Member
Joined
Apr 25, 2023
Messages
8
Location
Texas
Ordered and installed the new valve and drained the hydraulic system. When separating the valve body from the valve body pack a huge amount of metal shaving came out. Pls see the pictures for details. After assembly the lift boom will stop about halfway up in the raised position and will only go up if you accelerate the motor. Wondering what the next best step is? The shavings and debris came from somewhere. Wondering if the lift cylinders internally are scored and beginning to lock down from a seal leaking, pump failure, etc.
 

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Nige

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Thinking a bit more about it you are probably in for some major disassembly work (the tilt & steering circuits in addition to the lift) because all the hoses and valves will have contamination in them. The tank will also be full of particles. Each hose on the machine will probably need the sponge gun and every valve disassembled & cleaned.
 

Dieselham1

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Joined
Apr 25, 2023
Messages
8
Location
Texas
Nige, does this machine have a screen that can be cleaned for the hydraulic system and where would it be?
 

Nige

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Jun 22, 2011
Messages
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G..G..G..Granville.........!! Fetch your cloth.
Nige, does this machine have a screen that can be cleaned for the hydraulic system and where would it be?
With the quantity of debris in the photos above even a screen or filter will not remove everything or anywhere close to it. There is a suction screen in the hydraulic tank and also screens in the pilot and main control valves. To remove the screen from the tank will need the oil to be drained (see your O&M for procedure) first, but you're going to be draining it anyway so no problem there. The inspection cover on top of the tank will also need to come off so that the tank can be cleaned internally.

Please be under no illusions, you have major contamination in that system. Unless it is properly cleaned out you are simply setting yourself up for more failure(s), and hydraulic parts tend to be expensive. The finer debris will now be everywhere that is fed with hydraulic oil. The implement system, steering, brakes, and the hydraulic fan circuit will all be contaminated because the same tank is common to all of them
 
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