Item
Description
Action
Charge pump
The charge pump is damaged or has been installed
with the incorrect rotational orientation.
Verify that the charge pump is in good working
order and that it is correctly installed. Repair or
replace it as necessary.
SCR (system check / relief) valves
The SCR valves are malfunctioning or improperly
set.
Verify that the SCR valves are operating and
properly set. Repair or replace them as necessary.
Neutral difficult or impossible to find
Item
Description
Action
Input control signal (linkage, current, or
pressure)
A faulty control signal is being received at the
pump. (MDC - binding or broken linkage, EDC -
faulty or inadequate electrical signal, HDC -
blocked or incorrectly orificed control lines)
Verify that the input signal being received is
correct and identical in both directions. Adjust,
clean, repair, or replace control module as
necessary.
System pressure
With no input signal to the control, a pressure delta
may exist between the two sides of the working
loop.
Readjust pump neutral setting. Refer to
Swashplate
neutral adjustment
on page 22.
Servo pressure
With no input signal to the control, a pressure delta
may exist across the servo piston.
Readjust the control neutral setting. Refer to
Manual Displacement Control Neutral-Return Bracket
Adjustment
on page 23 and
Electric Displacement
Control/Hydraulic Displacement Control Neutral
Adjustment
on page 24
PCP pressure (EDCs only)
With no input signal to the control, a pressure
difference may exist across the control spool.
Replace the EDC.
System response is sluggish
Item
Description
Action
Reservoir oil level
There is an insufficient amount of hydraulic fluid,
resulting in an inadequate supply for the system
loop.
Fill the reservoir to the proper level with clean
hydraulic fluid.
Input control signal
(linkage, current, or pressure)
A faulty control signal is being received at the
pump. (MDC - binding or broken linkage; EDC -
faulty or inadequate electrical signal; HDC -
blocked or incorrectly orificed control lines)
Verify that the input signal being received is correct
and identical in both directions.
Pump control
A damaged pump control or control spool will not
correctly transmit the control input signal to the
pump.
Verify that the pump’s control is operating properly
and that the control spool is not damaged or worn
and moves freely within its bore. Clean, repair, or
replace it as necessary.
Bypass valve
A partially activated bypass valve causes cross port
leakage.
Verify that the bypass valve is closed and that the
valve is seating properly. Clean, repair, or replace it as
necessary.
SCR (system check / relief) valves
One or both of the SCR valves may be binding
within their bores.
Verify that the SCR valves operate freely. Repair or
replace them as necessary.
Charge pressure (in neutral)
There is low charge pressure resulting from a
damaged charge pump or low charge pressure
relief valve setting.
Inspect the charge pump for damage and verify the
charge pressure relief valve setting. Repair or replace
as necessary.
Charge pressure (in stroke)
There is low charge pressure resulting from internal
leakage within the system.
Repair or replace the component or components
within the system causing the internal leakage.
Service Manual
Series 40 M46 Variable Pumps
Troubleshooting
16 |
©
Danfoss | September 2017
11026743 | AX00000027en-US0202