TM 5-3805-280-24-1
Diagnostic Information
Engine and Pump Controller
Front and Rear Pump Control
Propel Speed Switch
(EPC)
Valve
Operational Function
To change propel speed.
To control engine speed, pump and
To send a regulated pilot
valve operations.
pressure signal to pump
regulators in responds to the flow
rate through neutral passages in
control valve.
Control Problems
No electrical signal sent to engine
Problems may differ depending on
Pressure signal to regulator does
and pump controller.
the malfunction.
not increase when a function is
actuated. Pump stays at
minimum flow.
Machine Symptoms
For open circuit, propel speed stays
Problems listed indicate malfunction
For rear pump control valve: left
at slow speed when switch is turned
in EPC. With key switch on, EC
propel cycle time slow, swing
to fast speed (rabbit).
motor does not go to start position;
also slow; cycle time for bucket,
engine starts and run at slow idle.
boom or arm almost normal. For
Engine speed does not change.
front pump control valve: bucket
Pump stays at minimum, all
cycle time very slow, boom not
functions are slow.
raised when leveling, right propel
cycle time slow; cycle time for
boom, arm, or swing almost
normal.
Laptop Computer with
--
--
--
Excavator Diagnostic
Software Self-Diagnostic
Functions
Laptop Computer with
Monitor No. 26, Propel speed switch.
--
Monitor No. 1, Front pump
Excavator Diagnostic
control pressure and No. 6, Rear
Software Monitoring
pump control pressure.
Function
Harness Check
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--
--
9025
Notes
Check switches and sensors in
Check fuses before replacing EPC.
--
15
propel speed control circuit.
8
Description of Operation
See Propel Motor Speed Change
See Engine and Pump Controller
See Pump Control Valve
Circuit Operation in Group 9025-05.
Circuit Theory of Operation in Group
Operation in Group 9025-05.
9015-15.
Continued on next page
TX,15,GG2238
1913AUG987/10
6-97
