15 - 2
Fault Probable Cause Action
2 All hydraulic rams slow to operate. Neutral circuit or low pressure Check pipe lines and replace as required.
lines leaking, damaged, trapped
or kinked.
Low pump flow. Check pump flow, if required service or
replace pump.
Priority valve operating. Check if the priority valve is sticking,
rectify as required.
Main relief valve (MRV) Check and adjust as required.
setting incorrect.
Unloader valve Check if unloader valve is sticking, i.e.
dumping flow from pump section P2.
Tank filter by-pass valve Check condition of hydraulic filter
Hydraulic tank breather Clean or replace the breather
3 One hydraulic service fails to Associated service pipe lines , Check hoses, replace as required.
operate or is slow to operate. leaking damaged, trapped
or kinked.
Associated ram leaking. Complete ram leakage check, replace
seals as required.
Auxiliary relief valve (ARV) Check and adjust as required.
setting incorrect.
Associated valve block section Check for leaks, rectify as required.
leaking or not operating. Also, see fault 6 'Leaking Oil Seal
(Control Valves)'.
Make sure that the associated load hold
check valve is operating.
Check that the control lever and
associated linkages is operating
the spool, rectify as required. Also, see
fault 5, 'A spool is Sticking'.
Check valve malfunctioning Test check valve, rectify as required.
(if fitted, e.g. stabiliser circuit)
Hose burst protection valve Test HBPV, service as required.
(if fitted) malfunctioning.
Piston rod is bent Replace piston rod, check pressure
settings of MRV and ARV.
Check that associated pivot pins are
adequately greased
4 The engine tends to stall when M.R.V setting incorrect. Check and adjust as required.
hydraulics are under load.
Poor engine performance. Check engine performance, see
transmission section for stall speed
test procedures.
Unloader valve pressure Check pressure setting of the
setting too high unloader valve.
Section E
Hydraulics
9803/3280
Section E
15 - 2
Issue 1
Fault Finding
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