Lull 944E-42 Service Manual User Manual download pdf (Page 385)

100

101

8.133

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

Hydraulic System

Not

Check the flow at the end of the circuit at

the male coupler.

Repair/replace pump

NOTE:

When checking pressures in

circuits, refer to Section 8.7,

“Hydraulic System Testing,” for

correct pressure readings.

NOTE:

Before pressure checking

circuits, refer to Section 9.8.29,

“Dual Joystick - Auxiliary

Hydraulic Circuit &

Troubleshooting,” to ensure the

electrical circuits for the pilot

select valve are functioning

Not

Check port relief at main control valve

Replace the relief valve on

auxiliary hydraulic section of

main control valve.

There are no auxiliary hydraulic

functions.

Not

Check the standby pump pressure at

implement pump pressure tap.

If OK

Replace unloader cartridge

on main control valve.

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.

Not

Inspect pump. Refer to

Hydraulic Testing

pages 8.12 through 8.54.

Check the cycle times for boom LIFT

and boom EXTEND to determine pump

performance. Pump flow directly

controls these cycle times. Refer to

Section 2.5.6, “Hydraulic Cylinder

Performance Specifications,” for correct

cycle times.

If OK

Not

Adjust/replace main relief

cartridge on main control

valve.

If OK

Not

Repair/replace joystick.

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

&auxiliary hydraulic section of main

control valve. Check pilot pressure. With

the button pressed and joystick moved

all the way to the left the pressure

should be 444 ±22 psi (30,6 ±1,5 bar).

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 385

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