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Cat 322bl sn 8nr20091. Left track slower than the right, will…

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Cat 322bl sn 8nr20091. Left...
Cat 322bl sn 8nr20091. Left track slower than the right, will walk straight when activating another function eg swing, arm etc, I've been told one side of the main pump could be getting tired, hence the machine will walk straight when only one side of the pump drives both tracks. It does have 15000 hrs on it so a worn pump would be reasonable, could it be a drive motor?
Submitted: 8 years ago.Category: Construction and Road Equipment
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Answered in 1 hour by:
2/22/2014
Mechanic: catmastertech, Technician replied 8 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,969
Experience: Field service technician for CAT 19 years.
Verified

Hello,

If the drive motor was the problem, it would never walk straight.

The pump is in two parts and the main control valve is in to parts. If one pump is slow/weak, it would also impact the implement functions.

A the easiest way to find performance problems is to perform cycle time testing.

 

 

 

Cylinder Operating Speed (seconds)
ItemNewRebuildService Limit
BoomExtension3.3 ± 0.34.3 max.5.0 max.
Retraction2.6 ± 0.33.4 max.3.9 max.
StickExtension4.0 ± 0.35.2 max.6.0 max.
Retraction2.9 ± 0.33.8 max.4.4 max.
BucketExtension4.2 ± 0.35.5 max.6.3 max.
Retraction2.3 ± 0.33.1 max.3.6 max.

 

Let me know how these test come out and we can get deeper into this problem.

 

Just so you know, all the right side controls work the right side of the valve and the left works the left.

The left hand control is in SAE settings are swing and stick with left travel.

Right side SAE pattern is boom and bucket with right travel.

Also the valves share sides with boom and stick flows combined. So, if one pump is weak, boom and stick will loose the most speed.

 

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Customer reply replied 8 years ago

Hi Donnie,


 


I have done the cylinder op speed test as accurately a s I can, results are as follows.


 


Boom ex 6.08


Boom re 6.72


Stick ex 4.12


Stick re 3.33


Bucket ex 4.61


Bucket re 2.78


 


Serial number is XXXXX not 20091


 


Kind regards


Adrian Zorzo

Mechanic: catmastertech, Technician replied 8 years ago

I would think you have a problem with the straight travel spool. This spool is how the flow changes from two pump flow to one pump flow an implement is used during travel.

This spool is located directly behind the main relief valve. A plug is on top and the spool can be removed from the top. If you have a problem installing the spool after inspecting it, you will need to remove the cap on the bottom due to the centering spring must fit into the bottom of the spool.

 

Check this spool for debris in the ports. Loose plug on the end or damage that may cause sticking or binding.

I would recommend removing it from the bottom to check the spring as well. I have seen one break.

Have you checked the pump pressures?

What are they if you have them?

 

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Customer reply replied 8 years ago

I haven't checked pump pressures, I will check the straight travel spool and get back to you .


 


thankyou


 


Adrian

Mechanic: catmastertech, Technician replied 8 years ago
Ok, if you need anything else, just let me know what you have found and we can work from there.
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Customer reply replied 8 years ago

Cat 322bl sn 8NR00291:


 


Hi Donnie, sorry for the late reply, I've been a bit ill.


 


I've removed straight spool and it seems fine, both springs look as per diagram in my manual.


 


I've noticed on the proportional reducing solenoid on the pilot manifold some damaged wiring, could this have a negative effect?


 


Could cleaning the spool with some emery paper help?


 


Kind regards


 


Adrian Zorzo

Mechanic: catmastertech, Technician replied 8 years ago

I hope you are feeling better. I have been fighting a cold myself. That time of year again.

 

If the spool felt rough or was hard to remove from the body, then polishing would help.

Any scar you can hang a fingernail on when sliding over it, is a concern. It may not stop it from moving but, it would be a sign metal is in the system.

 

The proportional reducing valve (PRV) controls the output of both pumps. Not just one side. This PRV solenoid is used to reduce the load on the engine by reducing the angle of the swash plates inside the pump.

 

You may have a sticking valve in the pump control head and this is causing the weak pump action.

Testing the pump pressures is the next step. You will see the two port near the outlet hoses of the pump that feed to the main control valve. You need two gauges to see the output of both pumps when a two pump flow demand is made.

 

The boom up, stick out and stick in are two pump flow demands. Swing, bucket and each travel control is a single pump demand.

 

The other port next to the two pump output taps is for the power shift pressure the PRV solenoid controls.

 

Pump output can be as high as 5500 psi in travel and 4900 psi for implement functions.

 

The power shift pressure will shift from 70 to 400 psi for pump regulation.

 

 

Test these pressures and post the results for each function and we can see if something shows up as a problem.

Use a large metal bar or pin to lock the track sprocket next to the frame to see the travel pressure max reading.

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