OM4012.2 Maintenance - Section 4 Automatic Lube System Reciprocating Pump Page 4-15 4. Grease Reservoir: For the 930E, the Cannister or Reservoir (6, Figure 4-2) is mounted on the right side front bumper in front of the upright frame support (View A-A, Figure 4-3). The reservoir has an approximate capacity of 50 lbs. (23 kg) of grease. System Operation: 1. During truck operation, with the pump and timer systems in a rest state, a preset time interval occurs. 2. The solid state system timer sends out a 24 VDC signal to energize SV1, causing it to open. 5. Vent Valve (11, Figure 4-2 or 10, Figure 4-3): With the vent valve closed, the pump continues to cycle until maximum pressure is achieved.
As this occurs, the vent valve opens and allows the grease pressure to drop to 0, so the injectors can recharge for their next output cycle. 3. As SVI opens, the resulting hydraulic fluid pressure flows through the pressure reducing valve closing the vent valve and also flows on to SV2. 4. The pressure reducing valve lowers hydraulic fluid pressure to the operating range of the hydraulic pump [maximum pressure 300 p.s.i. (2069 kPa)]. 5. 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 cylinder movement back and forth, thus causing a “pumping” action. 6. 24 VDC Solid State System Timer (Not Shown): The Solid State System Timer 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 stabil- ity. Its operating temperature range is -20°F to 131°F (-29°C to 55°C). 6. The cycle timer/flasher sends a pulsing signal, 1 second “On” and 1 second “Off” (adjustable), to SV2.
Solenoid valve SV2 directs the hydraulic fluid to the pump at 30 cycles/minute. 7. Pressure Switch (N/C 2000 psi [13 790 kPa]): (9, Figure 4-3) opens the 24 volt supply to the pump cycle timer, when the grease line pressure exceeds this limit. 7. With the vent valve closed, the pump continues to cycle until lubricant pressure rises to 2,000 psi (13 790 kPa) and the injectors have metered grease to the points of lubrication. NOTE: Depending on truck model, the specific pressure at which this switch opens, may vary. Therefore, all references in this coverage to the specific N/C 2000 psi [13 790 kPa] pres- sure switch would also change .
Refer to the truck Parts catalog for a specific switch installation . 8. If system pressure rises above 2000 psi (13 790 kPa), the N/C pressure switch will open until the timed cycle is complete and the solid state system timer terminates the 24VDC signals to SV1 and SV2. (See NOTE: below step 11.) 10. As SV1 is de-energized, the hydraulic fluid stops flowing to the pressure reducing valve and the vent valve allowing it to open. 9. As SV2 is de-energized the pump stops cycling. 8. Injectors (11 & 12, Figure 4-3): each injector deliv- ers a controlled amount of pressurized lubricant to a designated lube point. Refer to Figure 4-3 for locations. 11.
As the vent valve opens, the grease pressure drops to zero (0), so the injectors can recharge for their next output cycle. NOTE: When the N/C pressure switch opens, SV2 is de-energized causing the pump to stop; however, until the timed cycle is complete, SV1 remains energized, keeping the vent valve closed and holding pressure in the grease line. If the grease line pressure now drops to where the switch closes again, the pump will restart to hold grease line pressure, but the injectors will not recharge . 12. The system is now at rest, ready for another lube cycle and the sequence repeats itself.