Manitowoc 777 Service And Maintenance Manual

Reference Only
Manitowoc Published 10-01-2012, Control # 045-08 10-23
777 SERVICE MANUAL TROUBLESHOOTING
10
Problem 21
Jacking cylinder(s) will not extend or retract.
CHECKS
Check for 2,700 psi at lower accessory valve test port while manually enabling
jacking cylinder on lower accessory valve.
POSSIBLE CAUSES
Not in setup mode; Faulty control valve section;
Low pump pressure; Bad pump; Faulty counterbalance valve.
Check for 3,500 psi at lower accessory valve
test port while enabling another jacking cylinder.
2,700 psi or more 2,700 psi or less
Is crane setup mode selected and confirmed?
Yes No
Exchange both counterbalance valve
cartridges on problem jacking cylinder. Is
cylinder enabled with handle movement?
Adjust system pressure to 3,000 psi
when jacking handle is moved. (See
Test 21.)
2,700 psi or more
Replace counterbalance valve.
Repair or replace jacking cylinder.
Yes No
Select and confirm setup mode.
Does system develop any pressure?
Yes No
Repair or replace accessory pressure switch/wiring.

Manitowoc 777 Specifications

General

Brand	Manitowoc
Model	777
Category	Construction Equipment
Language	English