TROUBLESHOOTING 777 SERVICE MANUAL
10-24 Published 10-01-2012, Control # 045-08
Problem 22
Crawler pin cylinder(s) will not extend or retract (left or right set).
CHECKS
Check for 2,700 psi at lower accessory valve port while manually enabling crawler pin
cylinder handle on lower accessory valve.
POSSIBLE CAUSES
Not in setup mode; Faulty control valve section; Low
pump pressure; Bad pump; Mechanical problem.
2,700 psi or more 2,700 psi or less
Check for 3,000 psi at lower accessory test
port while enabling other crawler pin cylinder.
2,700 psi or more
Repair or replace problem
crawler pin cylinder.
Is crane setup mode select and confirmed?
Yes No
Select and confirm setup mode.
Does system develop any pressure?
Yes No
Adjust system pressure to 3,000 psi when
jacking handle is moved. (See Test 21.)
Repair or replace accessory
pressure switch/wiring.
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