CRANKING SYSTEM SYMPTOM DIAGNOSIS
Note. For cranking system symptom diagnosis charts (Scheme 1)and (Scheme 2).
Possible symptoms due to starting system trouble would be: starting motor does not run (or runs slowly), starting motor runs but fails to crank engine, and abnormal noise is heard. Proper diagnosis must be made to determine if the cause of each trouble lies in the battery, wiring harness, (including starting motor switch), starting motor or engine. Check following items and narrow down scope of possible causes. Check tightness of battery terminals (including ground cable connection on engine side) and starting motor terminals, discharge of battery, and mounting of starting motor.
Scheme 1
Scheme 2
STARTING MOTOR PERFORMANCE TEST
| CAUTION | Each test must be performed within 3 - 5 seconds to avoid coil from burning. |
Hold-In Test
With plunger out, disconnect negative lead from terminal "M". (Scheme 3) Check that plunger and pinion remain out. If plunger and pinion return inward, replace the magnetic switch.
Scheme 3
No-Load Performance Test
Connect battery and ammeter to starter. (Scheme 4) Check that starter rotates smoothly and steadily with pinion moving out. Check that ammeter indicates 90A maximum at 11V at 68°F (20°C).
Scheme 4
Plunger & Pinion Return Test
Disconnect negative lead from switch body. (Scheme 5) Check that plunger and pinion return inward. If plunger and pinion don't return, replace the magnetic switch.
Scheme 5
Pull-In Test
Note. Before testing, disconnect lead wire (3) from "M" terminal (2).
Connect battery to the magnetic switch. (Scheme 6) Check that plunger and pinion move outward. If plunger and pinion don't move, replace the magnetic switch.
Scheme 6
BRUSHES & SPRING TEST
Inspect brush springs for wear, damage or other abnormal conditions. Replace if necessary.
HOLD-IN COIL OPEN CIRCUIT TEST
Check for continuity across magnetic switch "S" terminal (1) and coil case. (Scheme 7) If there is no continuity, coil is open and should be replaced.
Scheme 7
GROUND TEST
Check the commutator and armature core. (Scheme 8) If there is continuity, the armature is grounded and must be replaced.
Scheme 8
OPEN CIRCUIT TEST
Check for continuity between segments. (Scheme 8) If there is no continuity at any test point, there is an open circuit and the armature must be replaced.
PULL-IN COIL OPEN CIRCUIT TEST
Check for continuity across magnetic switch "S" terminal (1) and "M" terminal (2). (Scheme 9) If there is no continuity, coil is open and should be replaced.
