Maintenance - Section 42 10/06 0M4206 Page 42-6 Automatic Lubrication System SYSTEM OPERATION 6. When 20685 kPa (3000 psi) grease pressure reaches pressure switch (4, Figure 42-6) set- ting, the switch contacts will close and energize relay K1 (12), removing power from grease pump solenoid valve (5) and the pump will stop. The relay will remain energized until grease pressure drops and the pressure switch opens again or until the timer turns off. Normal Operation Refer to Figure 42-5 and 42-6: 1. During truck operation, lubrication cycle timer (1, Figure 42-6) will energize the system at a preset time interval. 2.
The lubrication cycle timer provides a 24VDC signal through normally closed relay board (12) used to energize pump solenoid valve (3, Fig- ure 42-5), allowing hydraulic oil provided by the truck steering pump circuit to flow to the pump motor and initiate a pumping cycle. 7. After the pump solenoid valve is de-energized, hydraulic pressure in the manifold drops and vent valve (11, Figure 42-5) will open, releasing grease pressure in the lines to the injector banks. When this occurs, the injectors are then able to recharge for the next lubrication cycle. 3.
The hydraulic oil pressure from the steering cir- cuit is reduced to 2240 to 2413 kPa (325 to 350 psi) by pressure reducing valve (4, Figure 42-5) before entering the motor. In addition, the amount of oil supplied to the pump is limited by flow control valve (6). Pump pressure can be read using pressure gauge (5) mounted on the manifold. 8. Unloader valve (10) prevents excessive grease pressure if the pressure switch fails to close and shut off the hydraulic supply to the pump. The unloader will open at approximately 27.6 MPa (4000 psi). 9. The system will remain at rest until the lubrica- tion cycle timer turns on and initiates a new grease cycle. 4.
With oil flowing into the hydraulic motor, the grease pump will operate, pumping grease from the reservoir to vent valve (11) and then to injectors (13). Pressure switch (9) prevents over pressurization. 10. During the normal lubrication cycle, if grease pressure fails to reach 13790 kPa (2000 psi) at the pressure switch located on the rear axle housing, an amber indicator light will illuminate on the overhead panel. 5. During this period, the injectors will meter the appropriate amount of grease to each lubrica- tion point. FIGURE 42-5. HYDRAULIC SCHEMATIC 1. Hydraulic Oil Return 2. Hydraulic Oil Supply 3. Pump Solenoid Valve 4. Pressure Reducing Valve 5. Pressure Gauge 6.
Flow Control Valve 7. Hydraulic Motor 8. Grease Pump 9. Pressure Switch (NO) 10. Unloader Valve 11. Vent Valve 12. Orifice 13. Injector Bank