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Automatic Lubrication System - Section 42
Page 42-4
Pump Cycle Timer
[Also called a "flasher" timer, because it contains an
LED that illuminates when there is power going to
SV2]: Pump cycle timer (7, Figure 42-1) mounts on
SV2 solenoid and generates a timed pulse signal
which causes the solenoid valve to move, alternately.
The alternating movement of the valve, changes the
direction of hydraulic fluid flow from the top of the
pump cylinder to the bottom, and vice versa, causing
the grease pump piston to reciprocate, or pump.
Grease Reservoir:
Grease reservoir (6, Figure 42-1) is mounted on the
right deck structure to the right of the hydraulic cabi-
net just above the right front suspension.The reser-
voir has an approximate capacity of 29 l (7.7 gal) or
27 kg (60 lb) of grease.
Vent Valve
When SV1 solenoid is energized, hydraulic pressure
closes vent valve (11, Figure 42-1), and also causes
the pump to cycle. The pump cycles until SV1 sole-
noid is de-energized. When this occurs, hydraulic
pressure is removed, causing the vent valve to open.
The grease pressure drops to 0, and the injectors
recharge for their next output cycle.
24 VDC Solid State System Timer
The solid state system timer (not shown) sends out a
24 VDC timed-interval signal to energize the solenoid
valves, causing the grease pump to operate. This
timer is mounted in the cab (in the housing under the
passenger seat) to insure temperature stability. Its
operating temperature range is -29°C to 55°C (-20°F
to 131°F).
Lube Injectors
Each injector (10, Figure 42-2) delivers a controlled
amount of pressurized lubricant to a designated lube
point. Refer to Figure 42-2 for locations.
Safety Unloader Relief Valve
Safety unloader relief valve (not shown) is located on
the back of vent valve (11, Figure 42-1). The safety
unloader is designed to open if the pressure in the
grease line rises to approximately 27.5 MPa (4000
psi)*. If this valve opens, the grease is expelled to the
atmosphere.
*NOTE: This setting is not adjustable.
WARNING: Exceeding 24.1 MPa (3500 psi) will
damage components and/or cause components
to rupture, resulting in possible serious injury to
any nearby personnel.
System Operation
During truck operation, with the pump and timer sys-
tems in a rest state, a preset time interval (2.5 to 80
minutes) occurs.
The solid state system timer sends out a 24 VDC sig-
nal to energize SV1, and the flasher timer on SV2.
As SVI opens, the hydraulic fluid pressure flows
through the pressure reducing valve and on to SV2.
The pressure reducing valve lowers hydraulic fluid
pressure to the operating range of the hydraulic
pump [maximum pressure 2069 kPa (300 psi)]. This
pressure also signals the vent valve, causing it to
close.
After the system pressure has been reduced, it
passes on to SV2. Each operation of SV2 moves the
hydraulic cylinder which operates the grease pump.
As SV2 turns on and off (refer to cycle timer/flasher
below), it changes the direction of the hydraulic cylin-
der movement back and forth, thus causing a pump-
ing action.
The cycle timer/flasher sends a pulsing signal, 1 sec-
ond ON and 1 second OFF (adjustable), to SV2.
Solenoid valve SV2 directs the hydraulic fluid to the
pump at 30 cycles/minute.
OM4202
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