Template Name: OML_1_col Template Date: 1994_04_22
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844/642 Telehandler
HYDRAULICS
BOOM EXTEND CYLINDER TROUBLESHOOTING NOTE: If the extend cylinder will extend but will not retract, replace the counterbalance valve on the extend cylinder. Does the boom extend without a capacity load?
NO
YES Test the pressure at the test port on MP on the. flow divider. Lower the boom to the end of the cylinder stroke and hold. Does the pressure gauge read 3000 psi (207 bar)?
Follow the Control and Park Brake Pilot Pressure Troubleshooting procedure. Is the problem in the controls?
YES Repair or replace the malfunctioning control components.
YES Use an in-line pressure gauge to test the extend pressure at the extend cylinder. Does the pressure gauge read 2500 psi (172 bar)?
YES Repair or replace the extend cylinder.
NO Adjust the extend pressure relief valve in the control valve and retest the extend pressure. Does the gauge read 2500 psi (172 bar)?
YES If the extend/retract does not work after adjusting the relief valve, repair or replace the extend cylinder.
NO Repair or replace the extend control valve and/or the extend relief valve. NO Use an in-line flowmeter to test the pressure at the EF port of the priority flow divider. Does the pressure gauge read 3000 psi (207 bar)? NO Remove and bench test the hydraulic pump. Does the hydraulic pump meet specifications?
YES Adjust the relief valve in the Main Control Valve. Open the load control valve of the flowmeter and hold the joystick in the boom lower position. Does the gauge read 3000 psi (207 bar)?
YES Remove the flowmeter.
NO Replace the relief valve in the Main Control Valve. NO Repair or replace the hydraulic pump.
YES Replace the priority flow divider.
PRINTED IN U.S.A.
601-6
913250
