Hydraulic System; All Controls Inoperative; All Boom Functions Inoperative; No Main Boom Up - Skyjack SJ45 AJ+ Service Manual

Hydraulic System

4.3 Hydraulic System

4.3-1 All Controls Inoperative

1. Broken or defective drive pump shaft or coupling. Check pump shaft and coupling. Replace if
2. Hydraulic oil level low.

4.3-2 All Boom Functions Inoperative

1. Open or defective dump valve 2H-21A.
2. Stuck or defective relief valve RV6.
3. Stuck or defective Inlet Compensator/ differential
sensing valve DSV1.
4. System pump P2 defective.
5. Plugged or defective high pressure filter F1.

4.3-3 No Main Boom Up

1. Stuck or defective lift up valve 4H-14.
2. Stuck or defective shuttle valve SV6.
3. Stuck or defective check valve CV10.
4. Stuck or defective differential sensing valve
DSV4.
5. Stuck or defective counterbalance valve CB9.
6. Defective lift cylinder C3.
SJ45 AJ+
Section 4 – Troubleshooting Information
defective.
Check oil level. Fill to proper level.
Clean valve. Check O-rings on valve. Check
operation of valve. Repair or replace valve as
required.
Set valve to specifications. Check O-rings and
clean valve. Repair or replace valve as required.
Check O-rings and clean valve. Check operation of
valve. Repair or replace valve as required.
Test pump with flow meter. Replace if defective.
Check filter. Replace if plugged or defective.
Clean valve. Check operation of valve. Repair or
replace valve as required.
Clean valve. Check O-rings on valve. Check
operation of valve. Repair or replace valve as
required.
Clean valve. Check operation of valve. Repair or
replace valve as required.
Clean valve. Check O-rings on valve. Check
operation of valve. Repair or replace valve as
required.
Clean valve. Check O-rings on valve. Repair or
replace valve as required.
Check seals on cylinder. Replace as necessary.
Replace cylinder if defective.
238274AAA
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