DOWEL-REACTION 1M3150 - Caterpillar

All Caterpillar Machines And Engines Equipped With PrelubIntroduction
Prelub uses the starter motor to run an oil pump which primes the engine oil system before starting. This information applies to machines using the Caterpillar Prelub system that is equipped with the 125-6935, 139-1585, and 140-3108 Timer Assemblies. There are other prelubrication systems that are installed on machines made by Caterpillar, but this Special Instruction is not applicable to these other systems.
Normal Operation
1. Turn the key switch to the CRANK position and hold the switch in the CRANK position.2. The starter motor runs in Prelub Mode. The motor spins but the flywheel is not engaged. The starter motor runs for 3 to 45 seconds until oil pressure reaches between 27 kPa (4 psi) and 48 kPa (7 psi). The oil pressure is measured at the Prelub oil pressure switch.3. The key switch is still held in the CRANK position. The starter is delayed for 3 seconds and spinning stops.4. The starter then engages the flywheel and the engine is cranked normally.Basic Operation Of The Prelub Timer
Basic Prelub Electrical Schematic
Circuitry Of The Timer (1) Relay Control.(2) 3 Second Delay Control.Power from the keyswitch is supplied to contact 1 of the timer when the keyswitch is in the CRANK and RUN positions. Contact 1 supplies power to the electronic circuits that are inside the timer. Contact 2 connects through the wiring harness to the ground terminal on the starter solenoid. When the Prelub oil pressure switch detects pressure less than 4 psi, contact 4 is connected to ground. Power from contact 3 (CRANK) then passes through the normally closed internal relay. The Prelub mag switch is then energized. When the Prelub mag switch closes, current flows to the motor terminal on the starter solenoid. The starter motor is allowed to run without engaging the starter drive.
When the Prelub starter motor runs, the Prelub pump will pressurize the oil system. The Prelub pump draws oil from the engine oil pan. The oil is then pumped into the engine oil system through the oil hoses of the Prelub system. The oil pressure is measured at the Prelub oil pressure switch. When the oil pressure exceeds 27 kPa (4 psi) to 48 kPa (7 psi), the timer turns off the Prelub mag switch. The starter motor will stop turning. The timer will wait for 3 seconds. Then, an internal relay in the timer will allow power from the key switch (contact 3) to pass through contact 5 on the timer. Now, the starter will crank normally. If the key switch is turned OFF for less than 2 minutes before another crank attempt, Prelub will not activate. The starter will crank normally. The timer is located on the electric circuit between the key switch and the transmission ECM. The timer is also located on any electric circuits that might exist between the key switch and other controls or devices that prevents cranking.
Initial Troubleshooting Procedure
During Prelub Mode, the starter motor runs but the drive is