s e c t i o n "condition of parts in boom and bucket
MAIN SPOOL
section" for service procedure.
ACTUATING PRESSURE
CONDITION OF PARTS IN
I n s t a l l a 3000 psi (210,92 kg./cm 2 ) hydraulic
I N L E T CONTROL SECTION
gauge in the same port used for measuring hydrau-
lic relief pressure. With hydraulic fluid at operating
A malfunction in the inlet control section will af-
t e m p e r a t u r e and the engine at high free idle it
fect both the boom and bucket operations. If either
should take 300 to 600 psi (21,09 to 42,18 kg./cm.2)
the boom or bucket circuits operate correctly, the
to actuate a spool in the main valve when a pilot
problem is probably not in the inlet section. Refer
spool is moved.
to the Troubleshooting Guide.
EXAMPLE: Engine at high free idle-Move the
boom lever to the boom up position-read 300 to
CONDITION OF PARTS IN
600 psi (21,09 to 42,18 kg./cm. 2) on the gauge as
BOOM AND BUCKET SECTIONS
soon as the lever has been actuated, Do not force
the hydraulics over relief.
A malfunction not found in the inlet control sec-
tion usually is either in just the boom section or
Measure the main spool actuating pressure in
just the bucket section. However, it is good to ex-
amine both sections if repairs are to be made on
each of the positions, boom up and down, bucket
either one. Refer to the Troubleshooting Guide and
up and down. An actuating pressure greater than
600 psi could indicate a sticky spool. Refer to the
Disassembly Procedures.
TROUBLESHOOTING GUIDE
REMEDY
PROBLEM
CAUSE
1. Flow restricted in lines to
1. Clean or replace lines
1. Pressure reads above 100
and from pilot valve.
PSI with both pilot valve
spools in neutral and the
engine at high idle.
2. Flow restricted in the pilot
2. Clean or replace cap
pressure supply cap.
3. Flow restricted in pilot valve.
3. Inspect pilot valve for location
of restriction. Clean or replace
valve if necessary.
4. Main flow control poppet and
4. Clean and remove all foreign
relief valve assembly stuck in
material and contamination.
closed position.
Replace any damaged o-rings
or back-up rings.
5. Remove return line and clean
5. Flow restricted in the return
line from the main control
or replace as necessary.
valve.
2. Boom will not raise or
raises slowly.
1. Ruptured supply line to the
1. Replace line
(a) Low pressure readings.
pilot valve.
2. Pilot valve spool not
2. Free any binding linkage. Check
positioning properly.
for damaged spool or detent
balls and replace as necessary.
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