257d turns to right on startup

[Stavi01]

Hi everyone, we have a 257d skid loader. As soon as the machine is started, it will begin turning itself to the right. The only way to make it stop, is to release the parking brake and wiggle the left joystick. Wondering if anyone has come across this before. Problem seems worse when machine is first started for the day. Otherwise it runs and operates like normal. I suspected a solenoid on top of the pump, but after swapping them the problem didn’t change. I also started machine with all solenoids unplugged, it still moved, but would stop once parking brake was released and joystick was moved. I appreciate anyone could give.

 

[Nige]

Based on your described symptoms the signal from the LH joystick is a possible culprit.
I'm not sure this will work but try disconnecting the 8-pin wiring harness connector right at the bottom of the LH joystick, then start the engine and see what happens.
Does the machine have any Diagnostic Codes showing.?
A Serial Number would be a good idea. There are 8 models of 257D, it would be nice to know which one you have.

EDIT: It would also be a good idea to check for any electrical system "modifications" that have resulted in safety systems being bypassed.

 

[Stavi01]

Hi, Thanks for your response!
Ser. No. Cat0257daezw01823

active codes
3700-3 bucket inclinometer sensor voltage above normal

logged codes
70-3 parking brake switch voltage above normal
2685-8 left drive motor speed sensor #1 abnormal pulse
2686-8 left drive motor speed sensor #2 abnormal pulse.

I unplugged the joystick and with the machine on jack stands the left track moves forward. Plugged joystick back in, same thing, until park brake is pressed and joystick is moved just a touch. Then it sounds like pressure is released quickly and the track will bounce then stop. As machine idles you can hear the pump start to sound like it is laboring a little and if left joystick is touched, left track will bounce a little and pump noise goes away briefly.

 

[Nige]

active codes - 3700-3 bucket inclinometer sensor voltage above normal

Pretty normal. "They all do that sir."

70-3 parking brake switch voltage above normal
2685-8 left drive motor speed sensor #1 abnormal pulse
2686-8 left drive motor speed sensor #2 abnormal pulse.

Those three get me twitchy even though they are Logged not Active. It might be well worth your time to go through all the electrical connections for the parking brake switch and the speed sensors in the machine harness right the way from the ECM to the switch/sensor as appropriate. I can send you an Electrical Schematic if you don't have one.

I unplugged the joystick and with the machine on jack stands the left track moves forward. Plugged joystick back in, same thing, until park brake is pressed and joystick is moved just a touch. Then it sounds like pressure is released quickly and the track will bounce then stop.

Not the joystick if those are the symptoms then. It almost sounds as though a "counter-signal" in reverse from the joystick is enough to negate whatever is causing the LH track drive system to turn in a forward direction.

 

[Stavi01]

Hey thanks again!!!
I would love the schematic. If you could send it that would be wonderful.

The part that makes zero sense to me, is if I unplug the four drive motor solenoids on top of the pump, it does the exact same thing, the motor will move by itself, and release when joystick is touched. However you have no drive controls with the joystick. Is there another solenoid I should be looking for? Possible issue in valve housing? Thanks again!

 

[Nige]

Having had a bit more time to think about it the symptoms could point to either a broken centring spring or a sticking swashplate inside the rear section of the pump that drives the LH track. The directional control solenoid on top of the pump has no "neutralising" function (e.g. spring, etc.) inside it. Therefore when the solenoid receives a neutral signal from the joystick it is the centring springs inside the pump that move the swashplate back to the neutral position.

The PWM position sensor on the joystick should output around 50% duty cycle in the centre (neutral) position, 5% duty cycle when fully stroked in one directio, and 95% when fully stroked in the opposite direction. If you have a DMM capable of measuring duty cycle you can check those numbers to prove that the joystick position sensor is functioning correctly.

I sent you some stuff. Check your PMs.