TM-5-2350-378-24-P
HYDRAULIC DIAGNOSTIC CENTER (HDC) SUPPORTING ARMORED COMBAT EARTHMOVER (ACE), M9
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL INCLUDING REPAIR PARTS AND SPECIAL TOOLS LIST
TM-5-2350-378-24-P - Page 49 of 790
TM 5--2350--378--24&P
0004 00--24
INTRODUCTION TO TROUBLESHOOTING AND REPAIR OF THE M9 ACE HYDRAULIC
SYSTEM -- Continued
0004 00
GENERAL SUSPENSION TROUBLESHOOTING INFORMATION
1.
PRESSURE CHECKS: The 2,800--2,900 psi (19,306 -- 19,996 kPa) maximum suspension system
pressure is controlled by an adjustment on the compensating pump. This adjustment should always be
checked prior to performing suspension system pressure checks. The suspension system pressure checks
can then be performed as specified in the troubleshooting procedures.
2.
SUSPENSION SYSTEM RELIEF VALVE: The sole function of this valve is to protect the suspension
hydraulic circuit in the event the pressure control device on the pump should fail. This valve is set to open at
3,700--3,800 psi (25,512--26,201 kPa).
3.
DESCRIPTION OF THE SPRUNG SUSPENSION CIRCUIT: When the SPRUNG/UNSPRUNG control
lever is in the SPRUNG position, the operator has no control over the suspension. The height of the vehicle
is automatically controlled by leveling valves in the No.1 and 4 actuators. Each No.1 and 4 actuator and its
paired No. 2 or 3 actuator is independent of the other three corners (fully independent suspension).
Therefore, the SPRUNG suspension system can be considered as consisting of five major areas as follows:
a. The right rear pair of actuators.
b. The left rear pair of actuators.
c.
The right front pair of actuators, with the right front bump stop cylinder.
d. The left front pair of actuators, with the left front bump stop cylinder.
e. The power system: pump, suspension relief valve, SPRUNG/UNSPRUNG valve, and the main accumu-
lator.
When the suspension will not raise, the most probable cause is excessive internal leakage in one or more
components. The troubleshooting procedures eliminate these major areas from the circuit one by one to locate
the fault.
4.
DESCRIPTION OF THE UNSPRUNG SUSPENSION CIRCUIT: When the SPRUNG/UNSPRUNG
control lever is placed in the UNSPRUNG position, the operator assumes control of the four front actuators.
However, the four rear actuators remain in an automatic mode. Hydraulic valves in the No.1 and 4 actuators
shift position to cause all four rear actuators to share a common pressure line (the two rear No. 4’s are no
longer independent). This is necessary so the front of the vehicle can be tilted (one front side of the vehicle
lowered more than the other side). Therefore, problems can develop in either the front or rear areas of the
suspension hydraulic system that could affect performance in the SPRUNG mode only, the UNSPRUNG
mode only, or both modes.
5.
OPERATIONAL VEHICLE: The vehicle should be considered operational if it will rise within 2 minutes of
engine start and will stay up long enough to perform its mission.
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