The pilot pressure of both valves is generated separately within each valve. The combination valve uses the pilot pressure reducing valve to generate the pilot pressure. The implement control valve uses the pilot relief valve to generate the pilot pressure.
Note: The pilot pressure of the combination valve is adjustable. The pilot pressure of the implement control valve is not adjustable.
Before you start the test procedure, perform the following procedure that is listed in the reference.
Reference: Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.
| Required Tools | ||
| Part Number | Description | Quantity |
| 198-4240 | Digital Pressure Indicator | 1 |
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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak. |
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| NOTICE |
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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, "Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on products. Dispose of all fluids according to local regulations and mandates. |
Combination Valve
- Remove the cover from the left side of the machine.
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| Illustration 1 | g00993017 |
- Repeat Step 1 on the right side of the machine.
- Remove two wing nuts (2) and screen assembly (1) .
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| Illustration 2 | g00993020 |
- Repeat Step 3 on the other side of the machine.
- Remove four bolts (4) and cover (3) .
- Connect the 198-4240 Digital Pressure Indicator to pressure tap (5). Pressure tap (5) is located on the combination valve at port location "PS2".
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| Illustration 3 | g00906659 |
(5) Pressure tap (pilot supply pressure) (PS2) . | |
Note: The pressure tap is number four from the top of the combination valve.
- Start the engine. Move the hydraulic lockout control to the UNLOCKED position.
- Warm the hydraulic oil to normal operating temperature. Normal operating temperature is 45 °C (115 °F) to 70 °C (160 °F). Use the following procedure in order to warm the hydraulic oil.
- Operate the engine at 1800 RPM to 2000 RPM.
- Extend the lift arms until the cylinders bottom out.
- Operate the tilt cylinders back and forth until you reach the normal operating temperature.
- When the machine is at rest, pilot pressure and standby pressure will be the same pressure. With the engine at low idle, check the pilot supply pressure at pressure tap (5). The pilot system pressure should be 2590 + 170 kPa - 70 kPa (375 + 25 psi - 10 psi). You must activate an implement circuit in order to raise the standby pressure higher than idle pressure. This must be performed in order to check the pilot pressure.
- If the pilot system pressure is correct, proceed to Step 12. If the pilot system pressure is not correct, proceed to Step 11.
- Loosen locknut (7) and turn adjustment screw (6) until the pilot system pressure is 2590 + 170 kPa - 70 kPa (375 + 25 psi - 10 psi). Then, tighten locknut (7) .
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| Illustration 4 | g00864860 |
Location of Pilot Pressure Reducing Valve on the Combination Valve | |
- Move the work tool to the fully raised position.
- Move the hydraulic lockout control to the LOCKED position.
- With the engine at low idle, attempt to lower the work tool to the ground. Check pilot supply pressure at pressure tap (5). The pilot system pressure should be 0 ± 100 kPa (0 ± 15 psi).
- If the pilot system pressure is correct, perform Step 16. If the pilot system pressure is not correct, replace the solenoid valve for the pilot system that is located on the combination valve.
- Move the hydraulic lockout control to the UNLOCKED position and lower the work tool to the ground. Move the hydraulic lockout control to the LOCKED position. Shut off the engine.
- Install the screens and the covers on the machine.
Reference: For more information, refer to the service manual for Disassembly and Assembly for the machine that is being serviced.
Implement Control Valve
- Remove the access plate on the front frame of the machine.
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| Illustration 5 | g00865160 |
- Connect the 198-4240 Digital Pressure Indicator to pressure tap (8) on the implement control valve.
Note: The pilot pressure at pressure tap (8) is for the collector arms. Pilot pressure for the remaining implements is supplied from the combination valve.
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| Illustration 6 | g00865089 |
- Start the engine. Move the hydraulic lockout control to the UNLOCKED position.
- Ensure that the oil in the hydraulic system is at normal operating temperature.
- With the engine at high idle, fully open or fully close the collector arms on the felling head. At the same time, check the pilot pressure at pressure tap (8). The pilot pressure should be 3500 ± 1000 kPa (510 ± 145 psi).
- Return the engine to low idle. Move the hydraulic lockout control to the LOCKED position. Shut off the engine.
- Install the cover on the front frame of the machine.