jcb 1CX, Service Manual

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12 - 12
Hydrostatic Pump
from machine no. 751012
Pump Neutral Adjustment
Adjustment procedure
! !
WARNING
The following procedure requires the machine to be
disabled (wheels raised off the ground, work function
disconnected etc.) while the work is carried out.
HYD 8-1/1
Place the machine safely onto blocks, so that all four wheels
are clear of the ground. Ensure that the machine is stable.
Position the operator’s seat facing forwards so that the
brakes are released.
1 Identify which pump section requires adjustment.
If the machine veers to the left this could be caused by
either the right hand wheels moving forward or the left
hand wheels moving in reverse. Remember that pump
P1 drives the left hand motor and pump P2 drives the
right hand motor.
If the machine moves either straight ahead or behind
then both pump servos must be adjusted equally.
2 Stop the engine.
3 Remove the floor plates.
4 Loosen locknut A and turn the ‘neutral’ adjusting screw
B 1/10 of a turn in the required direction then re-tighten
the locknut.
If the wheels are creeping forward, turn the adjusting
screw in a clockwise direction (looking underneath the
pump). If the wheels are creeping in reverse, turn the
screw anti-clockwise.
Note: This adjustment is very sensitive. Turn the adjusting
screw 1/10 of a turn at a time and re-check. A slight
movement when the wheels are raised is acceptable
provided that no movement occurs when the machine is
resting on the ground.
5 Start the engine and check that the wheels are
stationary.
6 Finally tighten locknut A to 23 Nm (17 lbf ft), taking care
to retain the set position of adjusting screw B.
7 Re-check for wheel movement.
Section E Hydraulics
9803/8550
Section E
12 - 12
Issue 2
Pumps
S244940
A
B
P1
P2
This procedure may be carried out if the machine creeps when the drive joystick is in the neutral position. This fault may be due
to an incorrect neutral setting of the servo piston. Before attempting any adjustment, carry out the following preliminary checks.
Check tyre pressures The pressure of one tyre may be low or one or both tyres on one side of the machine may be new
and condition and the other tyres worn. In both these cases the rolling circumference of the tyres will be unequal
causing the machine to veer to one side.
Check chain tension Chains which are tensioned unequally will cause the machine to veer to one side. Always adjust the
tension on all four chains, never just one.
Check brake release Low pressure or faulty seals may cause the brake to drag on one side. Check the pressure at the
pressure, seal failure anti-stall valve. Check the seal by using a hand pump to release the brake and see if the pressure
holds.
Check the drive joystick Check that the joystick spools are not sticking and are correctly operated by the lever.
Note: If the fault cannot be rectified by any of the above checks or adjustment, then either the pump or motor could be faulty. To
identify which, swop the motor feed hoses at the pump. If the machine now veers in the opposite direction then the pump is
faulty. If the machine continues to veer in the same direction the the motor is faulty.
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