TROUBLESHOOTING (Continued)
Problem
Cause
Correction
Machine loses power after
Diverter valve on prime move
Diverter valve may need rebuilding or
operating satisfactorily
leaking or bypassing oil internally
replacing.
initially
through valve to reservoir
Excessive back pressure
Relieve condition. Restriction may be
from outlet to reservoir.
Relief valve setting in backhoe
Relief pressure will have to be checked
control valve too low or defective
and corrections made. Backhoe
system pressure is 2000 PSI (CBH60),
2250 PSI (CBH70), 2550 PSI (CBH80),
Relief valve may need cleaning and
overhauling, or entire cartridge must be
replaced.
Loss of power in lift or
Spool not moved to full stroke
Check spool travel - should be .16”
crowd cylinder, but other
either way or a total of .32” for CBH60.
cylinders function properly
Check spool travel- should be .28”
either way, or a total of .56”. for
CBH70 and CBH80.
Overload relief valve in the control
Clean relief carefully but do not disturb
valve stuck open or malfunctioning
its pressure setting as it cannot be field
calibrated, or replace cartridge.
Problems involving the control
This valve is a precision device and is
valve
not intended for any extensive field
adjustment or repair. Field replace-
ment parts are limited to seal kits,
cartridges, valve sections and tie rods.
Replacement of these parts, the
opening of check cavities and certain
relief cavities to examine for trapped
dirt, or resetting of the main relief valve
with the use of good pressure gauge,
should be referred to qualified service
personnel.
Dirt and shreds of packing material are
the usual causes of valve malfunction.
Be sure the reservoir oil supply is kept
clean and only factory supplied
packings are used in cylinder repair.
Everything must be clean and free of
dirt during oil line removal and
replacement, and during any cylinder
work.
Loss of power in any one
Loose oil line connections,
Tighten all hose connections and
cylinder, including lift
leaks in line or broken lines
replace any damaged O-rings at
and crowd
leaking O-ring fittings. Check and
replace any damaged hoses and lines.
Restrictions in oil lines
Check and replace any damaged hoses
and lines. Check for pinched hoses.
Oil is bypassing cylinder piston,
Replace or rebuild the cylinder; replace
scored piston, worn piston packing
damaged parts.
or defective piston assembly
19
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