Lull 944E-42 Service Manual User Manual download pdf (Page 341)

100

101

8.89

Model 644E-42/944E-42 Rev. 6/04

Hydraulic System

NOTE:

When checking pressures in

circuits, refer to Section 8.7,

“Hydraulic System Testing,” for

correct pressure readings.

Not

Check seals on lift/lower cylinder. Repair/replace lift/lower

cylinder.

If OK

Not

Check counterbalance valve on lift/

lower cylinder.

Replace the counterbalance

valve.

Not

Check pilot operated check valve on

lift/lower cylinder.

Replace the pilot operated

check valve.

If OK

Not

The lift/lower cylinder does not

lower.

Check the standby pump pressure

at implement pump pressure tap.

Replace unloader cartridge

on main control valve.

If OK

Not

Check pilot pressure at “PPG” port

of accumulator charge/secondary

function valve.

Adjust/repair/replace

pressure reducing cartridge

on accumulator charge/

secondary function valve.

If OK

Not

Adjust/replace main relief

cartridge on main control

valve.

If OK

Not

Repair/replace joystick.

Install pressure gauge in the pilot

supply line, between the rear

joystick and the extend/retract

section of main control valve.

Check pilot pressure. With the

joystick moved all the way to the

right, the pressure should be

444 ±22 psi (30,6 ±1,5 bar).

Check the main relief pump

pressure at implement pump

pressure tap. Refer to Section 8.7,

“Hydraulic System Testing,” test

sequence 7.

Install pressure gauge in the pilot

supply line, between the joystick &

pilot select valve and pilot select

valve & lift/lower section of main

control valve. Check pilot pressure.

With the joystick moved all the way

forward, the pressure should be

444 ±22 psi (30,6 ±1,5 bar).

Not

If the lift/lower cylinder

drifts or reacts slowly,

check the seals on the lift/

lower cylinder.

Replace counterbalance and/

or pilot-operated check valves

on the lift/lower cylinder.

Check counterbalance and

pilot-operated check valves.

Repair/replace lift/lower

cylinder.

If OK

Before troubleshooting any

hydraulic circuit, ALWAYS

begin by checking the

following:

1. Hydraulic oil level in the

reservoir

2. All hoses, tubes, fittings

for leaks, kinks,

interference, etc.

3. Air in the lines

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Lull 944E-42 Service Manual User Manual Page 341

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