Lull 944E-42 Service Manual User Manual download pdf (Page 462)

100

101

Hydraulic System

8.210

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

b. Checking Accumulator Recharge Pressure and

Nitrogen Pre-Charge

1. Park the vehicle on a firm, level surface, fully retract

all hydraulic cylinders, ground the attachment (if

any), place the travel select lever in the [N]

NEUTRAL DETENT position, engage the park brake

switch and shut the engine OFF.

2. With the engine OFF, pump the brake pedal

repeatedly until the accumulators are completely

discharged. ALL stored pressure should now be

removed from the brake accumulator system.

3. Remove the access plate (3) from the cab floor.

4. Locate the diagnostic test nipple (1) on the

accumulator charge/secondary function valve (2) in

the “SW” port. Attach a 3000 psi (207 bar) pressure

gauge to the test nipple.

5. Start the engine and allow the accumulators to fully

charge. Slowly pump the service brake pedal, while

closely watching the test gauge.

6. Record the lowest pressure observed before the

accumulator recharges. The pressure should be

950 - 1200 psi (65 - 83 bar). This reading is the

accumulator recharge pressure.

7. Record the highest pressure observed when the

accumulator charge valve shifts and unloads the

pump. This pressure should be 1900 - 2100 psi

(131 - 145 bar) and is the high limit. If the

accumulator charge valve does not reach the high

limit and continues to load the pump, refer to Section

8.13.4, “Accumulator Charge Troubleshooting,”

step 2.

8. If either of these readings are outside the

recommended ranges, the accumulator charge/

secondary function valve may need repair or

replacement. Section 8.12.13, “Accumulator Charge/

Secondary Function Valve.”

9. Shut the engine OFF.

10. Slowly pump the service brake pedal while closely

watching the pressure gauge.

11. Record the lowest pressure observed before the

pressure drops to nearly zero. This reading is the

nitrogen pre-charge of the accumulators. This

pressure should be approximately 450 psi (31 bar). If

there is any doubt about the pressure reading,

proceed to next step.

12. If the nitrogen charge pressure is not correct, follow

procedures in Section 8.13.2, “Pre-Charging

Accumulator.”

13. Remove the pressure gauge from the test nipple and

reinstall the protective rubber cap.

14. Reinstall the access plate (1) to the cab floor. Secure

in place with the capscrews. Torque the capscrews

to 18 lb-ft (25 Nm).

MU5950

MU3770

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