910K and 914K Compact Wheel Loaders Caterpillar

Piston Pump (Implement) Margin Pressure - Test and Adjust

Usage:

914K CD2

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Personal injury can result from hydraulic oil pressure and hot oil.
Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.

Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine.
To prevent personal injury or death, perform the following:
Park the machine on a smooth, level surface.
Lower the work tool to the ground and engage the parking brake.
Stop the engine and remove the key.

Block the wheels and install the steering frame lock.

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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, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products. Dispose of all fluids according to local regulations and mandates.

Specifications

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Table 1
Implement Margin Pressure
1700 ± 100 kPa (247 ± 15 psi) at 50 % Displacement

Introduction

This information includes the following test:

Piston Pump (Implement) Margin Pressure -Test and Adjust

Required Tools

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Illustration 1	g02571852
Tooling (A) 198-4240 Digital Pressure Indicator Gp

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Table 2
Required Tools
Tool	Item	Qty	Part No	Description
A			198-4240	Digital Pressure Indicator Gp
	A1	1	198-4234	Digital Indicator
	A2	2	198-4239	Pressure Sensor Gp (0 to 41,368 kPa (0 to 6,000 psi))
	A3	2	198-4236	Adapter Cable As

Test Preparation

Refer to Testing and Adjusting, "Machine Preparation for Testing and Adjusting".

For more information about relieving the hydraulic pressure, refer to the Service Manual module Testing and Adjusting, "System Pressure - Release"

Move the machine to a smooth, horizontal location that is away from operating machines and away from personnel.

Place the transmission direction in the NEUTRAL position.

Engage the parking brake. Place wheel blocks in front of the wheels and behind the wheels.

Lower the bucket or the work tool to the ground.

Stop the engine.

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Illustration 2	g03604065
View of left-hand side of hitch area.

Install the steering frame lock.

Piston Pump (Implement) Margin Pressure -Test and Adjust

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NOTICE

Permit only one operator on the machine. Keep all other personnel away from the machine or in sight of the operator.

Relieve the pressure in the hydraulic system.

Ensure that the engine start switch is in the OFF position.

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Illustration 3	g03603737
View of main implement valve pressure test tap location inside front frame from right side of hitch area.

Install tooling (A) on test tap of the main implement valve.

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Illustration 4	g03603917
View of implement load sense tap on the main implement valve through the hitch area in the front frame.

Install a second tooling (A) on the implement load sense test tap located in the front frame on the left side of the main implement valve.

Start the engine and warm the hydraulic oil to a normal operating temperature of approximately 49 to 65°C (120 to 150°F).

Run the engine at high idle.

Raise the lift arms slowly. While raising the lift arms slowly, record the differential pressure indicated on tooling (A). Refer to table 1 for the correct margin pressure specification. Margin pressure is the difference in pressure between the implement pump discharge pressure and the implement pump load sensing pressure.

Reduce the engine speed to low idle.

Lower the lift arms to the ground.

Turn the key switch to the OFF position.

Release the hydraulic pressure. Refer to the Service Manual module Testing and Adjusting, "System Pressure - Release".

Do not adjust the implement piston pump because of the result of this test. If the results are not acceptable, perform the testing for the piston pump implement low pressure standby and high-pressure stall. Also, perform the relief valve load sensing signal test before making any adjustments. Refer to the Service Manual modules Testing and Adjusting, "Piston Pump (Implement) Low Pressure Standby - Test and Adjust", Testing and Adjusting, "Piston Pump (Implement) High Pressure Stall - Test and Adjust", and Testing and Adjusting, "Relief Valve (Load Sensing Signal) - Test and Adjust".

If the pressure is correct, proceed to Step 14. If the implement pump margin setting must be adjusted and all other testing has been performed, perform the following steps:
1. Remove panel (1) which is below the cab entry door on the right side of the machine. Gain access to the implement pump (4) and implement pump pressure compensator valve (3) .
1. Loosen the locknut (5) .
1. As needed, adjust the pressure. Turn the adjustment screw (6) clockwise in order to increase the pressure. Turn the adjustment screw (6) counterclockwise in order to decrease the pressure.
  Note: When decreasing the pressure setting, turn the adjustment screw (6) counterclockwise below the needed pressure. Then, turn adjusting screw (6) clockwise to the correct pressure setting. This method of adjusting the pressure setting eliminates any free play in the adjusting screw threads.
1. Tighten locknut (5) .
1. In order to make sure that the pressure is correct, perform steps 5 through 11 again.