SERV1852-02
August 2008
TECHNICAL PRESENTATION
320D-336D HYDRAULIC EXCAVATORS -
TIER III ENGINES
MAIN HYDRAULIC PUMPS AND PUMP CONTROL
VALVE GROUPS
Service Training Meeting Guide
(STMG)
GLOBAL SERVICE LEARNING
320D-336D HYDRAULIC EXCAVATORS -
TIER III ENGINES
MAIN HYDRAULIC PUMPS AND PUMP CONTROL
VALVE GROUPS
AUDIENCE
Level II - Service personnel who understand the principles of machine systems operation,
diagnostic equipment, and procedures for testing and adjusting.
CONTENT
This presentation provides an introduction and describes the components and systems operation
of the 320D-336D main hydraulic pumps and pump control valve groups. Additional
presentations will cover the machine walkaround, engines, pilot system, main control valve
group, implements swing system, travel system, and tool control systems in more detail. This
presentation may be used for self-paced and self-directed training.
OBJECTIVES
After learning the information in this presentation, the technician will be able to:
1. identify the components and explain the operation of the 320D-336D hydraulic
excavators main hydraulic pumps and controls, and
2. diagnose problems in the main hydraulic pumps and controls.
REFERENCES
320D Hydraulic Excavator Specalog AEHQ5856
323D L and 323D LN Hydraulic Excavators HEHH3327

Nomenclature Change: During the fourth quarter of 2008, the 325D and 330D
nomenclature changed. The 325D became the 329D and the 330D became the 336D for
most arrangements.
The exceptions are as follows:
- The nomenclature for the 325D MH and 330D MH did not change.
- The nomenclature for the 325D FM and 330D FM did not change.
- The 325D HD HW did not change into 329D HD HW. This model is being discontinued.
However, the 330D HD HW changed to the 336D HD HW.
SERV1852-02 - 4 - Text Reference
08/08 Main Pumps
1
INTRODUCTION
This section of the presentation will cover the main hydraulic pumps and pump controls for the
300D Hydraulic Excavators.
The main pump group consists of a variable displacement piston drive pump and a variable
displacement piston idler pump. The drive pump and the idler pump are part of an integral
housing. The drive pump and the idler pump are identical in construction and operation.
The pumps are sometimes referred to as S.B.S. (side by side) pumps. The main difference
between all of the pumps is the maximum pump flow for each model.
Both the drive pump and the idler pump have individual pump control valve groups to control
the pump flow.
The 320D through the 329D use the same type of pump control valve group. The 330D/336D
pump control valve group is the same as the pump control valve group used on the 345C pump.
SERV1852-02 - 5 - Text Reference
08/08 Main Pumps
Stick Cylinder
Bucket Cylinder Boom Cylinders
Swing Motor Travel Motors
Pilot
Control

with constant horsepower control.
SERV1852-02 - 6 - Text Reference
08/08 Main Pumps
Engine Speed
Sensor
Engine
ECM
Machine
ECM
Pilot
Pump
Drive
Pump
Monitor
Engine
Speed Dial
POWER SHIFT PRESSURE
SYSTEM
Output
Pressure
Sensor
Idler
Pump
Pump Control
Valve
Power Shift
PRV Solenoid
OK
When the engine speed dial is on position 10 and a hydraulic load is placed on the engine, this
condition causes the engine speed to decrease below the engine's target rpm.

The PWM signal sent from the Machine ECM causes the proportional reducing solenoid valve
to regulate the pilot pressure to the pump control valve groups to a reduced pressure.
This reduced pressure is called power shift pressure (PS).
The output flow of the drive pump and the idler pump is controlled in accordance with the
power shift pressure. The power shift pressure is used to control the maximum hydraulic pump
output in relation to the engine rpm.
A decrease in engine speed causes an increase in power shift pressure and a decrease in pump
flow.
Solenoid
Spring
PROPORTIONAL REDUCING
SOLENOID VALVE

PWM SIGNAL INCREASE
Pilot Pressure
Power Shift Pressure
Tank
Plunger
When the speed dial is at dial position 10, if the Machine ECM senses a decrease in engine
speed below target rpm, the Machine ECM increases the PWM signal sent to the solenoid.
The magnetic force of the solenoid increases. As the magnetic force of the solenoid becomes
greater than the force of the spring, the spool moves down against the force of the spring.
The downward movement of the spool blocks the flow of oil to the tank.
More power shift pressure oil is now directed to the pump control valve group.
The increased power shift pressure acts on the drive pump control valve group and the idler
pump control valve group.
If both pumps are upstroked, then both pumps will destroke as a result of the increase in power
shift pressure. If only one pump is upstroked, only the upstroked pump will destroke.
SERV1852-02 - 9 - Text Reference
08/08 Main Pumps

The drive pump supplies oil to the right half of the main control valve group and the following
valves:
- stick 2 control valve
- boom 1 control valve
- bucket control valve
- attachment control valve
- right travel control valve
SERV1852-02 - 11 - Text Reference
08/08 Main Pumps
5
1
3
6
4
2
The idler pump supplies oil to the left half of the main control valve group and the following
valves:
- left travel control valve
- swing control valve
- stick 1 control valve
- boom 2 control valve
- auxiliary valve for tool control (if equipped)
The output of the variable-displacement piston pumps is controlled by the pump control valve
groups (5 and 6) mounted on the main hydraulic pumps.
SERV1852-02 - 12 - Text Reference
08/08 Main Pumps
6
This illustration shows the pump control valve group for the drive pump. Except for the power
shift solenoid, the components for the idler pump are identical.
The power shift PRV solenoid valve (1) provides a common power shift pressure for both

NFC: NFC pressure is the most significant controlling signal in a negative flow controlled
hydraulic system. Each pump control valve group receives a specific NFC signal that is based
upon the hydraulic demand for that specific pump.
SERV1852-02 - 14 - Text Reference
08/08 Main Pumps
U
U
M
Actuator
Idler
Pump
Drive
Pump
Pilot
Pump
Med Press
Pump
Main Control Valve
Group (Right Side)
Pilot Filter and
Manifold
Pilot Pump
Medium Pressure
Circuit
Main Control Valve
Group (Left Side)
Left NFC
Control
Orifice
Right NFC