FIFTH WHEEL LIFTS SLOWLY

TM 9-2320-285-24-2

3-40. FIFTH WHEEL HYDRAULIC SYSTEM TROUBLESHOOTING (CONT)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

2. FIFTH WHEEL LIFTS SLOWLY

Step 1. Check hydraulic control valve relief pressure (para 3-42c).

a. If pressure is less than 2000 psi, but more than 1500 psi, adjust (para 3-42c). If pressure increases

to 2000 psi without turning adjusting screw in all the way, refer to para 2-76, Malfunction 2, step 1. If

2000 psi pressure is not obtained or adjusting screw must be turned in all the way to obtain 2000 psi,

proceed to step 2 below.

b. If pressure is 2000 psi or less than 1500 psi, proceed to step 2 below.

Step 2. Install pressure gage in hydraulic control valve relief pressure check point (para 3-42c).

Install flowmeter at hose connecting hydraulic pump and hydraulic control valve.

CAUTION

Do not hold 5th WHEEL control lever back for more than 30 seconds at time. Failure to follow this

procedure could result in damage to hydraulic pump.

With vehicle engine operating at governed speed, have assistant pull back 5th WHEEL control lever fully.

Watch pressure gage and flowmeter. Pressure shall be 2000 psi with a flow rate of at least 10 GPM.

NOTE

With engine at governed speed, maximum performance is 14 GPM flow rate and 2000 psi relief pressure.

a. If flow rate is less than 10 GPM, hydraulic pump is defective; repair or replace (para 3-42a).

b. If flow rate is between 10 and 14 GPM, but relief pressure is less than 2000 psi, hydraulic control

valve is defective; repair or replace (para 3-42c).

3-410