Lull 944E-42 Service Manual - Manual (Page 462)

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).
B
A
1
2
MU5950
MU3770
3