Rolls-Royce Corniche - Starter Motor Fault Diagnosis

Workshop Manual Rolls-Royce Silver Shadow & Bentley TSeries
Chapter M
I Starter Motor Fault Diagnosis
1
Symptom I Possible Cause Action
I 1
Speed, torque and current
consumption low
Speed and torque low, current
consumption high
Armature does not rotate;
low current consumption
Armature does not rotate;
high current consumption
Excessive brush movement
causing arcing at commutator
Excessive arcing at the
commutator
(a) Battery in poor condition
(b) Faulty brushgear connections
(c) Commutator in poor condition
(d) Faulty connections
(a) Tight or worn bearings, bent
shaft, armature fouling a
pole-
shoe or cracked spigot on
drive end bracket
(b) Insufficient end float
(c) Short circuited armature
or field coils
(a) Open circuited armature field
coil
(b) Faulty solenoid unit
(c) If the commutator is badly
burnt there may be poor
contact between brushes and
commutator
(a) Earthed field winding or short
circuited solenoid unit
(b) Armature physically prevented
from rotating
(a) Check batiery
(b) Check connections
(c) Clean commutator and skim if necessary
(d) Check battery connections and earth
leads
(a) Examine components and renew if
necessary
(b) Check
armature end float
(c) Check circuits
( see Starter motor
Bench inspection)
(a) Check circuits (see Starter motor
- Bench
test)
(b) Check solenoid
(c) Check commutator and brushgear
(a) Check circuits (see Starter motor
- Bench
test)
(b) Remove starter motor from engine and
bench test, if the fault persists dismantle
starter to determine the fault
I (a) Defective armature windings
(a) Low brush spring tension
(b) Brushes worn
(c) Worn or eccentric commutator
(d) Thrown or high segment on
commutator
(b) Sticking brushes
, (c) Dirty commutator
(a) Check spring tension (see Brush
springs-
To service)
(b) Renew brushes
(c) Rectify by skimming ona lathe
(d) If a
segment(s) has been 'thrown', the
armature should be renewed
If a
segment(s) is 'high' the fault can be
rectified by skimming the commutator
on
a lathe
(a) Check circuit (see Starter motor
- Bench
test)
(b) Check brush spring pressure, and ensure
that the brushes are free to move in their
boxes
(c) Clean commutator; skim if necessary