Trouble Shooting - Shibaura ST318 Workshop Manual

5. TROUBLE SHOOTING

Condition
1. The implement does not raise even
with the control lever shifted to the
"RAISE" position.
2. The implement heavily hunts, with
the valve at neutral.
(moving up and down)
3. Raising speed of the implement is
slower than specified.
4. Unsmooth change-over by control
lever.
5. Abrupt rise of the oil temperature of
the tank.
Possible cause
(1) Too heavy implement.
(2) Oil pump does not discharge oil.
(3) Low relief pressure.
(4) Unload valve does not close.
(1) Damaged seat surfaces of lowering
valve and seat valve.
(2) Lowering valve does not attach
seat.
(3) Damaged seat surface of the check
valve.
(4) Damaged O-ring.
(Lowering valve, check valve seat.)
(5) Leakage in the cylinder.
(1) Damaged seat surface of the
unload valve.
(2) Damaged seat surface of the relief
valve.
(3) Leakage in the cylinder. *the same
with 2.
(4) Damaged O-ring. *the same with
2.
(5) Reduced volume efficiency.
(6) Clogged line filter.
(1) Dust between the body and spool ,
or damaged spool..
(2) Broken spring (for return).
(1) Seizure of oil pump.
(2) Decreased volume efficiency of oil
pump.
(3) Damaged seat surface of the
unloading valve.
(4) Damaged seat surface of the relief
valve.
(5) Excessive oil leakage in the
cylinder.
(6) Tractor is operated with the relief
valve working.
213
Remedy
(1) Check the implement.
(2) Replace the oil pump.
(3) Readjust the pressure.
(4)-1 Check if there is any dirt or
sticking at the unload valve.
(4)-2 If sticking, correct by lapping.
(Check oil contamination)
(1) Polish or replace lowering valve
and seat valve.
(2) Adjust unmoved condition.
(3) Polish seat surface or replace the
check valve seat.
(4) Replace O-ring.
(5) Check cylinder liner, piston oil seal
and piston, or replace if needed.
(1) Polish or replace the control valve
assembly.
(2) Replace valve seat.
(3) Check cylinder liner, piston oil seal
and piston. Replace if needed.
(4) Replace O-ring.
(5) Replace oil pump. (Check oil
leakage.)
(6) Wash and clean filter. (Check oil
contamination.)
(1)-1 Check the dust and remove it.
(1)-2 If the spool is damaged, replace
the body and spool.
(2) Replace the return spring.
(1) Replace the oil pump. (Check oil
contamination)
(2) – do –
(3) Replace the body and unload valve
in an assembly.
(4) Replace relief valve and valve seat.
(5)-1 Replace O-ring or oil seal.
(5)-2 Replace piston and cylinder
case.
(6) Adjust the feedback link.