CB-334D and CB-335D Paving Compactors Propel System Caterpillar

Piston Pump Neutral - Test and Adjust

Usage:

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Personal injury or death can result from sudden machine movement.
Sudden movement of the machine can cause injury to persons on or near the machine.

To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

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NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates.

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Illustration 1	g00954396
Brake Interlock Valve (1) Wiring harness for the brake solenoid

Set the brakes by disconnecting the wiring harness for brake solenoid (1). The wiring harness is identified by wire number 777-PU.

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Illustration 2	g00868862
Brake Interlock valve (2) Interlock Line (INT2) (3) Interlock Line (INT1)

Disconnect the lines for interlock line (2) and (3). Cap the fittings for the interlock line immediately. Connect the ends of interlock lines (2) and (3) together with a union. This will equalize the oil pressure on each side of the servo piston.

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Illustration 3	g00868865
Propel Pump (4) Forward Relief Valve Test Port (5) Reverse Relief Valve Test Port

Note: The pump is removed for photographic purposes.

Connect two 60000 kPa (8702 psi) pressure gauges into the ends of the test ports (4) and (5) .

Put the propel control lever in the LOW SPEED range. Start the engine. Run the engine at 1500 rpm.

Look at the pressure gauges. The difference in the pressure reading is the offset pressure.

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Illustration 4	g01042567
(6) Neutral Adjustment Screw (7) Locknut

Note: Replace the gauges with two 4000 kPa (580 psi) gauges in order to achieve finer resolution.

If the offset pressure is not zero, it is necessary to adjust the neutral position of the piston. In order to adjust the neutral position of the piston, loosen locknut (7) of the servo valve neutral adjustment screw (6) .

Turn the neutral adjustment screw (6) clockwise until the pressure gauge shows an increase in pressure. Mark the position of the screw.

Turn the neutral adjustment screw (6) counterclockwise until the other pressure gauge shows an increase in pressure. Mark the position of the screw.

Turn the screw clockwise to a position that is halfway between the positions that are marked.

Once the neutral has been found, hold the adjustment screw (6). Tighten locknut (7) to a torque between 28 N·m (21 lb ft) and 51 N·m (38 lb ft).

Stop the engine. Remove the pressure gauges. Remove the union from interlock line (2) and (3). Reconnect interlock lines (2) and (3) to the brake interlock valve. Reconnect the wiring harness (1) for the brake solenoid.