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catmastertech
catmastertech, Technician
Category: Heavy Equipment
Satisfied Customers: 1756
Experience:  19 years Cat, 3 years Case
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Hello, I just purchased a CAT 277B skid-steer w/ 760 hrs, like

Customer Question

Hello, I just purchased a CAT 277B skid-steer w/ 760 hrs, like new condition all around. The drive control has SERIOUS lag; about 1 second fwd, 1.5 second reverse, and terrible left-right control. I would not be able to operate this in tight places as it is all over the place. It's got new hyd filter, new oil, and the pump itself was tested for pressure. All is within specs. I brought it to the CAT dealer yesterday and they are still working on it. At their $95/hr, I am trying to do some of my own research. Do you have any ideas on what it can be??
Submitted: 4 years ago.
Category: Heavy Equipment
Expert:  catmastertech replied 4 years ago.

That is the spec for normal drives to engage.

Model Start to Move Forward. Start to Move Reverse.
267B/ 277B/ 287B 1 second max 1.5 seconds max

 

Steering response is different. Below are some of the guides they will use to check the machine.

 

The machine does not move correctly when the pilot operated hydraulic control ( hydrostatic) is actuated.

Probable Cause


The speed sensing valve may not be set correctly.

The charge pressure is too low.

The pilot operated hydraulic control ( hydrostatic) may not be functioning correctly.

The orifices at the pilot operated hydraulic control ( hydrostatic) may be plugged.

The piston motors may be worn or the pumps may be worn.

 

 

The machine is not modulating correctly.

Probable Cause


The oil temperature is too low.

There is a restriction in one of the pilot lines.

The pilot operated hydraulic control ( hydrostatic) is not functioning properly.

The piston pump is worn or damaged.

The piston motors are worn or damaged.

 

The machine does not track straight.

Probable Cause


The neutral null setting is incorrect.

The pilot operated hydraulic control ( hydrostatic) is not functioning correctly.

One section of the piston pump could be malfunctioning.

A piston motor may be malfunctioning.

The displacement stops on the piston pumps may need adjustment.

The orifices on the pilot operated hydraulic control ( hydrostatic) may be plugged.

 

My guess is they will focus on the joystick control.

catmastertech, Technician
Category: Heavy Equipment
Satisfied Customers: 1756
Experience: 19 years Cat, 3 years Case
catmastertech and 2 other Heavy Equipment Specialists are ready to help you
Customer: replied 4 years ago.
That is what they said- they will replace the joystick control. However, the unit is rather pricey and I do not want to be just swapping parts out. Is this a fairly common problem with these machines? What are the chances that the line off the joystick is blocked somewhere rendering it slow in each direction?
Expert:  catmastertech replied 4 years ago.

Both joysticks have the same source for pressure, both would have problems if it was from the source.

Yes, anything can happen to a line to cause it to block flow. If you have damaged anything or had a fire in the recent history, I would follow up on those repairs first.

Trash from a damaged hose can plug orifices. Sticking servo controls would plague Case units but, I have not seen that on Cat.

Please send me your serial number and I can check for service letters.

Customer: replied 4 years ago.
Hello, I will send you the serial # XXXXX; any additional help you can provide would be great! I will let you know what the issue was when it is resolved in case you come across this in the future. Thanks!
Expert:  catmastertech replied 4 years ago.
That is the best info I can get. I do work on these at the jobsites I go to but, the rental shop does the most repairs when they are off rent. I try to catch them to see what is the latest problems when ever I get into the shop.
Customer: replied 4 years ago.
Hello, I got a call today for the CAT tech & it turns out the ECM is only supplying 10 volts to the controls which is below what it should be. Further, once the joystick is released, the ECM does not quickly stop the power to the control therefore the machine keeps moving for up to a second.
Expert:  catmastertech replied 4 years ago.

I hate to second guess another tech but, this system is pilot hydraulic controlled. The ECM only serves as an interlock safety control. This prevents the machine operating without the safety bar down, an operator that weighs over a hundred pounds and the park brake switch released. Options for auxiliary controls will have a second ECM to switch flows and operate attachments.

I have not seen any speed or steering electronic controls on the B models. The only electric function is the on/off solenoid for each joystick. This simply sends or blocks oil flow to the joystick based on the command from the Interlock ECM.

It can cause the delay in starting to move if you press the park brake switch and try to move at the same time. When you release the joystick and it returns to center, the oil flow in the joystick is dumped to tank and the machine should stop moving.

 

I may be missing something here but, be sure to test run the unit before you pick it up from the dealer.

 

Customer: replied 4 years ago.
Don, could it be that perhaps the ecm was not sending full power to energize/unlock the solenoid that goes to the joystick, therefore blocking some flow? Perhaps I misunderstood over the phone but I will know more when I go to pick it up monday. I will keep you updated. Thanks!
Expert:  catmastertech replied 4 years ago.

Yes, I can see how it would be sluggish to start to move and weak steering input. I don't see how it would cause it to not stop moving. The machine should always stop quickly when the joystick is centered.

Replacing the joystick and the ECM would cover both problems.

Customer: replied 4 years ago.
Donnie, just to give you an update- the service tech at CAT changed the computer with absolutely no difference in machine performance/control. I did not think the ECM would do much for the hydraulics. Anyways, they then changed the joystick valve, about $850 part, and that completely solved the problem. The problem with the ECM change is that once it's in, it cannot be returned according to their policy so I am stuck paying for a part that needed no replacement. Anyways, if you ever run into something like this, I hope this helps you. Thanks for your help.
Expert:  catmastertech replied 4 years ago.

Thanks for the update. I wonder why they would not try the valve first?

I would push the issue a little. They could offer a goodwill policy adjustment or keep the new ECM as a shop tool to use as a test ECM. We have a couple of different models just for that purpose.

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