Grove Published 11-10-2014, Control # 524-00 2-69
RT880E SERVICE MANUAL HYDRAULIC SYSTEM
LOAD SENSE DUMP VALVE
Description
The Load Sense Dump Valve prevents Pump No. 1 from
coming on stroke during engine start. It is activated by the
Ignition Key Switch during the starting mode. This ensures
the engine does not attempt to start against a load in the
event the accumulators are charging or the fan motor is
activated.
The Load Sense Dump Valve consists of a solenoid actuated
two position two-way valve that is normally open and
deenergized during normal crane operation (Figure 2-37). In
this valve position the load sense circuit to the pump is
complete, allowing any load sense signal (pressure) from an
actuated function to stroke the pump to its full compensating
pressure of 4000 psi (27.6 MPa). Only during engine
cranking (ignition switch in the START position) does the
solenoid become energized, shifting the valve to a closed
position and directing any load sense signal (pressure) to the
reservoir, thereby preventing the pump from stroking and
building pressure over its standby pressure of 350 psi
(2.41 MPa).
Maintenance
Removal
1. Tag and disconnect the electrical connectors to the
valve.
2. Tag and disconnect the hydraulic hoses from the valve.
Cap or plug all openings.
3. Remove the capscrews, spring washers, and washers
securing the valve to the frame rail. Remove the valve.
Installation
1. Secure the valve to the frame rail with the washers,
spring washers and capscrews. Torque capscrews; refer
to Fasteners and Torque Values, page 1-15 for proper
torque value.
2. Connect the hydraulic hoses to the ports on the valve as
tagged during removal.
3. Connect the electrical connectors to the valve as tagged
during removal.
Functional Tests
1. Remove the electrical connector from the solenoid on
the Load Sense Dump Valve. Using a multimeter set to
measure voltage, probe the connector.
2. Turn the Ignition Switch to START and crank the engine;
verify 12 V is measured only when engine is cranking
(Ignition Switch in the START position).
3. Turn off engine.
4. Install the electrical connector onto the solenoid.
5. Install a pressure check diagnostic quick disconnect with
gauge onto the test port at the inlet tube of the Boom Lift/
Telescope/Hoist Valve Bank (see Figure 2-11).
6. With the engine off, discharge all of the pressurized oil
stored in the accumulators by depressing the Service
Brake Pedal on the cab floor 4-6 times or until the pedal
has no back pressure.
7. Turn the Ignition Switch to START and crank the engine
while observing the pressure gauge; during engine
cranking (ignition switch in the START position), a
pressure reading of 350 psi (2.41 MPa) should be
observed.
8. Turn off engine. Remove the diagnostic coupler.
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