MOTOR GP-ELEC HYD PUMP 3547543 - Caterpillar

Low nitrogen charge can cause early pump failure because of short cycle times between the cut-in and cutout operations of the accumulator charging valve.
1. Use the same equipment as used to check the nitrogen charge in the accumulator.2. Valve (7) on chuck (8) must be turned in completely (clockwise). Open valve (4).3. Start the engine and allow it to run until it is warm. As oil flows into the bottom of the accumulator, the air, and then the oil, will be pushed out of the top through the test equipment. When the oil flow stops, the top of the accumulator will be free of air.4. Close valve (4) completely.5. Stop the engine and push the brake pedal several times. This will permit the oil pressure in the brake system to be removed. The piston in the accumulator will be at the top of the accumulator.6. Put a charge of nitrogen in the accumulator. Follow the procedure in Steps 7 through 12 in the Accumulator Charge Procedure. The charging cycle will take longer because the piston will have to be moved to the bottom and the oil will have to be moved out of the accumulator.Transmission Neutralizer Pressure And Limit Switch
Transmission Neutralizer Switch Location
The parking brake limit switch assembly is not shown in this illustration.
Make reference to the S on the first page of the Testing And Adjusting section.
This section describes only the troubleshooting method to determine if the transmission neutralizer pressure switch or the neutralizer limit switch is operational.The transmission neutralizer pressure switch is normally closed. The switch is wired in parallel with a normally closed limit switch located above the left brake pedal assembly. Both switches must be open before the transmission will neutralize. Use the following procedure to check the operation of the transmission neutralizer pressure switch and neutralizer limit switch.1. Start the engine and allow the hydraulic system to reach normal operating temperature.2. Engage the transmission in first speed forward, and while the machine is slowly moving, depress the left brake pedal. When the left brake pedal is depressed, the transmission will disengage and switch to neutral, while at the same time, apply the service brakes.Also at this time, the engine rpm will increase due to a no-load condition from the transmission. This will allow full hydraulic power for bucket or attachment operation. If the transmission does not switch to neutral, proceed with the next step.3. Install a 0 to 2000 kPa (290 psi) pressure gauge at location (B) on the brake system hydraulic schematic. Apply the service brakes. The gauge must indicate at least 790 kPa (115 psi) of hydraulic pressure for the transmission neutralizer pressure switch to open and switch the transmission to neutral.If there is not at least 790 kPa (115 psi) shown on the gauge, the transmission will remain engaged. If there is at least 790 kPa (115 psi) shown on the gauge, but the transmission fails to switch to neutral, proceed to Step 4.4. Check the neutralizer limit switch located