The starting system components form two separate circuits. A high-amperage feed circuit that feeds the starter between 150 and 350 amperes, and a low-amperage control circuit that operates on less than 20 amperes.
If the vehicle is equipped with an automatic transmission, battery voltage is supplied through the low-amperage control circuit to the coil battery terminal of the starter relay when the ignition switch is turned to the Start position. The park/neutral position switch is installed in series between the starter relay coil ground terminal and ground. This normally open switch prevents the starter relay from being energized unless the automatic transmission gear selector is in the Neutral or Park positions.
If the vehicle is equipped with a manual transmission, it has a clutch pedal position switch installed in series between the ignition switch and the coil battery terminal of the starter relay. This normally open switch prevents the starter relay from being energized unless the clutch pedal is depressed, preventing starter operation while the clutch disc and the flywheel are engaged. The starter relay coil ground terminal is always grounded on vehicles with a manual transmission.
When the starter relay coil is energized, the normally open relay contacts close. The relay contacts connect the relay common feed terminal to the relay normally open terminal. The closed relay contacts energize the starter solenoid coil windings.
The energized solenoid pull-in coil pulls in the solenoid plunger. The solenoid plunger pulls the shift lever in the starter. This engages the starter overrunning clutch and pinion gear with the starter ring gear on the manual transmission flywheel, or on the automatic transmission torque converter drive plate.
As the solenoid plunger reaches the end of its travel, the solenoid contact disc completes the high-amperage starter feed circuit and energizes the solenoid plunger hold-in coil. Current now flows between the solenoid battery terminal and the starter motor, energizing the starter.
Once the engine starts, the overrunning clutch protects the starter from damage by allowing the starter pinion gear to spin faster than the pinion shaft. When the driver releases the ignition switch to the On position, the starter relay coil is de-energized. This causes the relay contacts to open. When the relay contacts open, the starter solenoid plunger hold-in coil is de-energized.
When the solenoid plunger hold-in coil is de-energized, the solenoid plunger return spring returns the plunger to its relaxed position. This causes the contact disc to open the starter feed circuit, and the shift lever to disengage the overrunning clutch and pinion gear from the starter ring gear.
SOLENOID TEST
Remove the starter as described in this group. Then proceed as follows:
- Remove the wire from the solenoid field coil terminal.
- Check for continuity between the solenoid terminal and field coil terminal with a continuity tester Continuity Test Between Solenoid Terminal and Field Coil Terminal There should be continuity. If OK, go to Step 3. If not OK, replace the faulty starter assembly.
- Check for continuity between the solenoid terminal and the solenoid case Continuity Test Between Solenoid Terminal and Solenoid Case There should be continuity. If OK, go to Step 4. If not OK, replace the faulty starter assembly.
- Connect the solenoid field coil wire to the field coil terminal.
- Install the starter as described in this group.
RELAY TEST
The starter relay is located in the Power Distribution Center (PDC) in the engine compartment. Refer to the PDC label for relay identification and location.
Remove the starter relay from the PDC as described in this group to perform the following tests:
- A relay in the de-energized position should have continuity between terminals 87A and 30, and no continuity between terminals 87 and 30. If OK, go to Step 2. If not OK, replace the faulty relay.
- Resistance between terminals 85 and 86 (electromagnet) should be 75 ± 5 ohms. If OK, go to Step 3. If not OK, replace the faulty relay.
- Connect a battery to terminals 85 and 86. There should now be continuity between terminals 30 and 87, and no continuity between terminals 87A and 30. If OK, see the Relay Circuit Test procedure in this group. If not OK, replace the faulty relay. Starter Relay .
RELAY CIRCUIT TEST
- The relay common feed terminal cavity (30) is connected to battery voltage and should be hot at all times. If OK, go to Step 2. If not OK, repair the open circuit to the PDC fuse as required.
- The relay normally closed terminal (87A) is connected to terminal 30 in the de-energized position, but is not used for this application. Go to Step 3.
- The relay normally open terminal (87) is connected to the common feed terminal (30) in the energized position. This terminal supplies battery voltage to the starter solenoid field coils. There should be continuity between the cavity for relay terminal 87 and the starter solenoid terminal at all times. If OK, go to Step 4. If not OK, repair the open circuit to the starter solenoid as required.
- The coil battery terminal (86) is connected to the electromagnet in the relay. It is energized when the ignition switch is held in the Start position. On vehicles with a manual transmission, the clutch pedal must be fully depressed for this test. Check for battery voltage at the cavity for relay terminal 86 with the ignition switch in the Start position, and no voltage when the ignition switch is released to the On position. If OK, go to Step 5. If not OK with an automatic transmission, check for an open or short circuit to the ignition switch and repair, if required. If the circuit to the ignition switch is OK, see the Ignition Switch Test procedure in this group. If not OK with a manual transmission, check the circuit between the relay and the clutch pedal position switch for an open or a short. If the circuit is OK, see the Clutch Pedal Position Switch Test procedure in this group.
- The coil ground terminal (85) is connected to the electromagnet in the relay. On vehicles with an automatic transmission, it is grounded through the park/neutral position switch only when the gearshift selector lever is in the Park or Neutral positions. On vehicles with a manual transmission, it is grounded at all times. Check for continuity to ground at the cavity for relay terminal 85. If not OK with an automatic transmission, check for an open or short circuit to the park/neutral position switch and repair, if required. If the circuit is OK, see the Park/Neutral Position Switch Test procedure in this group. If not OK with a manual transmission, repair the circuit to ground as required.
PARK/NEUTRAL POSITION SWITCH TEST
- Place the transmission gear selector lever in the Park position.
- Disconnect and isolate the battery negative cable.
- Raise and support the vehicle.
- Unplug the park/neutral position switch wire harness connector.
- Check for continuity between the center switch terminal and a good chassis ground. There should be continuity. If OK, go to Step 6. If not OK, replace the faulty switch.
- Move the transmission gear selector to the Reverse position and check for continuity between the center switch terminal and a good chassis ground. There should be no continuity. If not OK, replace the faulty switch.
CLUTCH PEDAL POSITION SWITCH TEST
The clutch pedal position switch is integral to the clutch pedal pushrod. It is located near the dash panel under the instrument panel. The wire harness connector for the switch is wrapped with foam tape.
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WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, REFER TO PASSIVE RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY. [/SIZE]
- Disconnect and isolate the battery negative cable.
- Unplug the clutch pedal position switch wire harness connector.
- Check for continuity between the two cavities in the switch-half of the wire harness connector with the clutch pedal released. There should be no continuity. If OK, go to Step 4. If not OK, replace the faulty switch.
- Check for continuity between the two cavities in the switch-half of the wire harness connector again with the clutch pedal depressed. There should now be continuity. If OK, see the Ignition Switch Test procedure in this group. If not OK, replace the faulty switch.
IGNITION SWITCH TEST
[SIZE=+1]
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, REFER TO PASSIVE RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY. [/SIZE]
- Disconnect and isolate the battery negative cable.
- Remove the steering column shrouds and unplug the ignition switch wire harness connector. Refer to Ignition Systems for the procedures.
- With the ignition switch in the On position, check for continuity between the ignition switch fused B(+) circuit terminal and the ignition switch output (start) circuit terminal. There should be no continuity. If OK, go to Step 4. If not OK, replace the faulty switch.
- With the ignition switch held in the Start position, check for continuity between the ignition switch fused B(+) circuit terminal and the ignition switch output (start) circuit terminal. There should now be continuity. If not OK, replace the faulty switch.
FEED CIRCUIT TEST
The starter feed circuit test (voltage drop method) will determine if there is excessive resistance in the high-amperage circuit. For circuit descriptions and diagrams, refer to 8W-21 - Starting System in Wiring Diagrams.
When performing these tests, it is important to remember that the voltage drop is giving an indication of the resistance between the two points at which the voltmeter probes are attached.
Example: When testing the resistance of the battery positive cable, touch the voltmeter leads to the battery positive cable clamp and the cable connector at the starter solenoid. If you probe the battery positive terminal post and the cable connector at the starter solenoid, you are reading the combined voltage drop in the battery positive cable clamp-to-terminal post connection and the battery positive cable.
The following operation will require a voltmeter accurate to 1/10 (0.10) volt. Before performing the tests, be certain the following procedures are accomplished:
- Battery is fully-charged. Refer to Battery for more information.
- Fully engage the parking brake.
- If the vehicle is equipped with an automatic transmission, place the gearshift selector lever in the Park position. If the vehicle is equipped with a manual transmission, place the gearshift selector lever in the Neutral position and fully depress the clutch pedal.
- Unplug the Automatic ShutDown (ASD) relay to prevent the engine from starting. The ASD relay is located in the Power Distribution Center (PDC) Refer to the PDC label for ASD relay identification and location.
- Connect the positive lead of the voltmeter to the battery negative terminal post. Connect the negative lead of the voltmeter to the battery negative cable clamp Test Battery Negative Connection Resistance - Typical Rotate and hold the ignition switch in the Start position. Observe the voltmeter. If voltage is detected, correct the poor contact between the cable clamp and the terminal post.
- Connect the positive lead of the voltmeter to the battery positive terminal post. Connect the negative lead of the voltmeter to the battery positive cable clamp Test Battery Positive Connection Resistance - Typical Rotate and hold the ignition switch in the Start position. Observe the voltmeter. If voltage is detected, correct the poor contact between the cable clamp and the terminal post.
- Connect the voltmeter to measure between the battery positive terminal post and the starter solenoid battery terminal stud Test Battery Positive Cable Resistance - Typical Rotate and hold the ignition switch in the Start position. Observe the voltmeter. If the reading is above 0.2 volt, clean and tighten the battery cable connection at the solenoid. Repeat the test. If the reading is still above 0.2 volt, replace the faulty battery positive cable.
- Connect the voltmeter to measure between the battery negative terminal post and a good clean ground on the engine block Test Ground Circuit Resistance - Typical Rotate and hold the ignition switch in the Start position. Observe the voltmeter. If the reading is above 0.2 volt, clean and tighten the battery negative cable attachment on the engine block. Repeat the test. If the reading is still above 0.2 volt, replace the faulty battery negative cable.
- Connect the positive lead of the voltmeter to the starter housing. Connect the negative lead of the voltmeter to the battery negative terminal post Test Starter Ground - Typical Rotate and hold the ignition switch in the Start position. Observe the voltmeter. If the reading is above 0.2 volt, correct the poor starter to engine block ground contact.
If the resistance tests detect no feed circuit problems, remove the starter and see the Solenoid Test procedure in this group.
Let me know how the test results are.
