Component Tests and General Diagnostics
COLD CRANKING TESTFor complete starter wiring circuit diagrams, refer to 8, Wiring Diagrams. The battery must be fully-charged and load-tested before proceeding. Refer to Battery in 8, Battery.
Fig.1 Volts - Amps Tester Connections - Typical:
1. Connect volt-ampere tester to battery terminals. See instructions provided by manufacturer of volt-ampere tester being used. Note: Certain diesel equipped models use dual batteries. If equipped with dual battery system, tester should be connected to battery on left side of vehicle only Also, tester current reading must be taken from positive battery cable lead that connects to starter motor.
2. Fully engage parking brake.
3. If equipped with manual transmission, place gearshift selector lever in Neutral position and block clutch pedal in fully depressed position. If equipped with automatic transmission, place gearshift selector lever in Park position.
4. Verify that all lamps and accessories are turned off.
5. To prevent a gasoline engine from starting, remove Automatic ShutDown (ASD) relay To prevent a diesel engine from starting, remove Fuel Pump Relay. These relays are located in Power Distribution Center (PDC). Refer to label on PDC cover for relay location.
WARNING: IF EQUIPPED WITH DIESEL ENGINE, ATTEMPT TO START ENGINE A FEW TIMES BEFORE PROCEEDING WITH FOLLOWING STEP.
6. Rotate and hold ignition switch in Start position. Note cranking voltage and current (amperage) draw readings shown on volt-ampere tester.
a. If voltage reads below 9.6 volts, refer to Starter Motor Diagnosis. If starter motor is OK, refer to Engine Diagnosis for further testing of engine. If starter motor is not OK, replace faulty starter motor.
b. If voltage reads above 9.6 volts and current (amperage) draw reads below specifications, refer to Feed Circuit Test in this section.
c. If voltage reads 12.5 volts or greater and starter motor does not turn, refer to Control Circuit Testing in this section.
d. If voltage reads 12.5 volts or greater and starter motor turns very slowly, refer to Feed Circuit Test in this section.
NOTE: A cold engine will increase starter current (amperage) draw reading, and reduce battery voltage reading.
FEED CIRCUIT TEST
The starter feed circuit test (voltage drop method) will determine if there is excessive resistance in high-amperage feed circuit. For complete starter wiring circuit diagrams, refer 8, Wiring Diagrams.
When performing these tests, it is important to remember that voltage drop is giving an indication of resistance between two points at which voltmeter probes are attached.
Example: When testing resistance of positive battery cable, touch voltmeter leads to positive battery cable clamp and cable connector at starter solenoid. If you probe positive battery terminal post and cable connector at starter solenoid, you are reading combined voltage drop in positive battery cable clamp-to- terminal post connection and positive battery cable.
The following operation will require a voltmeter accurate to 1/10 (0.10) volt. Before performing tests, be certain that following procedures are accomplished:
- Battery is fully-charged and load-tested. Refer to Battery in 8, Battery.
- Fully engage parking brake.
- If equipped with manual transmission, place gearshift selector lever in Neutral position and block clutch pedal in fully depressed position. If equipped with automatic transmission, place gearshift selector lever in Park position.
- Verify that all lamps and accessories are turned off.
- To prevent a gasoline engine from starting, remove Automatic ShutDown (ASD) relay. To prevent a diesel engine from starting, remove Fuel Pump Relay. These relays are located in Power Distribution Center (PDC). Refer to label on PDC cover for relay location.
Fig.2 Test Negative Battery Cable Connection Resistance - Typical:
1. Connect positive lead of voltmeter to negative battery cable terminal post. Connect negative lead of voltmeter to negative battery cable clamp. Rotate and hold ignition switch in Start position. Observe voltmeter. If voltage is detected, correct poor contact between cable clamp and terminal post.
Note: Certain diesel equipped models use dual batteries. If equipped with dual battery system, procedure must be performed twice, once for each battery.
Fig.3 Test Positive Battery Cable Connection Resistance - Typical:
2. Connect positive lead of voltmeter to positive battery terminal post. Connect negative lead of voltmeter to battery positive cable clamp. Rotate and hold ignition switch in Start position. Observe voltmeter. If voltage is detected, correct poor contact between cable clamp and terminal post.
Note: Certain diesel equipped models use dual batteries. If equipped with dual battery system, this procedure must be performed twice, once for each battery.
Fig.4 Test Positive Battery Cable:
3. Connect voltmeter to measure between battery positive terminal post and starter solenoid battery terminal stud. Rotate and hold ignition switch in Start position. Observe voltmeter. If reading is above 0.2 volt, clean and tighten battery cable connection at solenoid. Repeat test. If reading is still above 0.2 volt, replace faulty positive battery cable.
Note: Certain diesel equipped models use dual batteries. If equipped with dual battery system, this procedure must be performed on driver side battery only.
Fig.5 Test Ground Circuit Resistance - Typical:
4. Connect voltmeter to measure between negative battery terminal post and a good clean ground on engine block. Rotate and hold ignition switch in Start position. Observe voltmeter. If reading is above 0.2 volt, clean and tighten negative battery cable attachment on engine block. Repeat test. If reading is still above 0.2 volt, replace faulty negative battery cable.
Note: Certain diesel equipped models use dual batteries. If equipped with dual battery system, this procedure must be performed twice, once for each battery.
Fig.6 Test Starter Ground - Typical:
5. Connect positive lead of voltmeter to starter housing. Connect negative lead of voltmeter to negative battery terminal post. Rotate and hold ignition switch in Start position. Observe voltmeter. If reading is above 0.2 volt, correct poor starter to engine block ground contact.
Note: Certain diesel equipped models use dual batteries. If equipped with dual battery system, this procedure must be performed on driver side battery only.
6. If equipped with dual battery system (certain diesel equipped models), connect positive lead of voltmeter to positive battery cable clamp on battery located on left side of vehicle. Connect negative lead of voltmeter to positive battery terminal post on battery located on right side of vehicle. Rotate and hold ignition switch in Start position. Observe voltmeter. If reading is above 0.2 volt, clean and tighten battery cables at both batteries. Repeat test. If reading is still above 0.2 volt, replace faulty positive battery cable.
If resistance tests detect no feed circuit problems, refer to Starter Motor Diagnosis.
CONTROL CIRCUIT TESTING
The starter control circuit components should be tested in the order in which they are listed, as follows:
- Starter Relay
- Starter Solenoid
- Ignition Switch
- Clutch Pedal Position Switch - If equipped with manual transmission, refer to Clutch Pedal Position Switch.
- Park/Neutral Position Switch - If equipped with automatic transmission, refer to Park/Neutral Position.
- Wire harnesses and connections - Refer to Wiring Diagrams.