TROUBLESHOOTING 777 SERVICE MANUAL
10-16 Published 10-01-2012, Control # 045-08
Problem 14
Boom will not reach maximum speed.
POSSIBLE CAUSES
Partial control voltage from handle to PC; Partial control voltage from PC to pump EDC;
Pump or motor damaged.
CHECKS
When moving boom hoist control handle fully in both directions, diagnostic
BOOM HOIST screen (bank 1) obtains 100% handle control in each direction?
Yes No
Yes No
When moving boom hoist control handle fully in both
directions, diagnostic BOOM HOIST screen (bank 2)
obtains 100% pump control in each direction?
Repair or replace
control handle.
Check for pump leakage.
(See Test 21.)
Repair or replace coil or wiring.
Clean or replace orifice.
Consult dealer/
factory.
When moving applicable handle fully in both directions, does A1
diagnostic screen (bank 3) read 38 to 120 in lower or 136 to 215 in raise?
Yes No
Adjust handle center position (see Test 8).
Repair/replace control handle/wiring.
Remove plug at motor port M5 and check
orifice for obstructions. (See Test 15.)
Obstruction
No Obstruction
Is mast angle displayed greater than 23 degrees
and problem is with boom up?
No
Yes
Mast angle indicator problem.
Repair or replace indicator.
Is BOOM HOIST (bank 3) pressure above 3,200 psi?
Yes
No
Check pressure sender.
(See Test 9.)
Consult dealer/
factory.
Check for control voltage of +2.3 volts or more and coil
resistance of around 19 ohms at pump EDC. (See Test 13.)
Voltage and
Coil Ok
Voltage and/or
Coil not Ok
To Next Page
Loading...
