Automatic Lubrication System - Section 42 OM4202 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. 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. 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.
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. 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.
Vent Valve 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. 24 VDC Solid State System Timer 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 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). 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. 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.