UNABLE TO LIFT A LOAD (ALL OTHER FUNCTIONS NORMAL)

TM 10-3930-638-24&P

3-29. HYDRAULIC LIFT SYSTEM TORUBLESHOOTING (cont)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

UNABLE TO LIFT A LOAD (ALL OTHER FUNCTIONS NORMAL) (cont)

Step 3. With engine at idle speed and LIFT control lever in RAISE position (mast assembly will be at full

height), check for hydraulic oil leakage at gland assembly (located at bottom of lift cylinder assembly)

and at ring assembly (located at bottom of lift cylinder body).

a. If hydraulic oil leakage is observed, remove lift cylinder assembly (para 3-30e), and repair or

replace gland assembly or ring assembly (para 3-30e).

b. If hydraulic oil leakage is not observed, proceed to step 4.

Step 4. Start engine and operate at idle speed.

NOTE

Increase engine speed as necessary to prevent engine stall.

Place LIFT control lever in RAISE position and hold (mast assembly will be at full height).

Check control valve for hydraulic oil leakage.

a. Replace or repair control valve (para 3-30a) if hydraulic oil leakage is observed.

b. If hydraulic oil leakage is not observed, proceed to step 5.

Step 5. With engine off, operate control levers several

times to relieve hydraulic pressure.

Disconnect hose assembly connected between

control valve and lift cylinder assembly at con-

trol valve (refer to illustration).

Connect a 3000 PSI pressure gage between

elbow on control valve and hose assembly.

NOTE

Increase engine speed as necessary to prevent

engine stall.

Start engine and place LIFT control lever in

RAISE position until mast assembly is at full

height; continue to hold lever in RAISE posi-

tion.

Pressure gage shall indicate 2500-2550 PSI

with engine at full throttle.

a. If pressure gage indication is above or

below 2500-2550 PSI, adjust pressure

relief valve (para 2-48 b(2), step 23).

b . If pressure gage indication is between 2500-2550 PSI, remove and repair lift cylinder assembly

3-196