JUKI MOL-254 Engineer's Manual page 209

Trouble
4.Vibration is large.
5. Abnormal noise
6. Deformation in sewing shape
7. Cloth presser foot fails to go up or come
down.
Cause (1)
Grounding of the sewing machine is improper
Backlash between the oscillator and the hook
driving shaft is large.
Adjustment of the backlash of the X feed gear
is improper.
Adjustment of the backlash of the Y feed gear
is improper.
Moving torque in X direction is large.
Moving torque in Y direction is large.
Presser pressure is low.
There is looseness in the cloth feed base
ball.
Supplying air pressure is low.
Adjustment of the regulator is improper.
Presser lifting cylinder fails to properly
operate.
Solenoid valve fails to properly operate.
Lifting and lowering operation of the presser
is slow.
Cause (2)
Adjustment of the backlash between the
stepping motor gear and the X feed arm is
improper.
Adjustment of the backlash between the
stepping motor gear and the Y feed arm is
improper..
Adjustment of the regulator is improper.
Supplying air pressure is low.
The presser foot is bent.
Checking order and adjusting procedure
Securely fix the sewing machine with the level adjuster.
Adjust the oscillator.
Adjust the backlash of the X feed gear.
Adjust the backlash of the Y feed gear.
Adjust the backlash of the X feed gear.
Adjust the backlash of the Y feed gear.
Adjust the regulator.
Adjust the supplying air pressure.
Adjust the looseness.
Adjust the supplying air pressure.
Adjust the regulator.
Check the connector connection.
Replace the cylinder.
Replace the solenoid valve.
Replace the presser foot.