For troubleshooting on fuel injected engines, please refer to Driveability & Emissions Controls in this repair guide.
All fuel injected models (VG30i and Z24i) utilize a crank angle sensor in the distributor. This sensor controls ignition timing and has other engine control functions. There is no vacuum or centrifugal advance. All timing settings are controlled by the Electronic Control Unit (ECU).
The main differences between the 1976-77 and 1978 systems are: (1) the 1976-77 system uses an external ballast resistor located next to the ignition coil, and (2) the earlier system uses a wiring harness with individual eyelet connectors to the electronic unit, while the later system uses a multiple plug connector. You will need an accurate voltmeter and ohmmeter for these test, which must be performed in the order given.
- Check all connections for corrosion, looseness, breaks, etc., and correct if necessary. Clean and gap the spark plugs.
- Disconnect the harness (connector or plug) from the electronic unit. Turn the ignition switch ON . Set the voltmeter to the DC 50v range. Connect the positive (+) voltmeter lead to the black/white wire terminal, and the negative (-) lead to the black wire terminal. Battery voltage should be obtained. If not, check the black/white and black wires for continuity; check the battery terminals for corrosion; check the battery state of charge.
- Next, connect the voltmeter (+) lead to the blue wire and the (-) lead to the black wire. Battery voltage should be obtained. If not, check the blue wire for continuity; check the ignition coil terminals for corrosion or looseness; check the coil for continuity. On 1976-77 models, also check the external ballast resistor.
- Disconnect the distributor harness wires from the ignition coil ballast resistor on 1976-77 models, leaving the ballast resistor-to-coil wires attached. On 1978 models, disconnect the ignition coil wires. Connect the leads of an ohmmeter to the ballast resistor outside terminals (at each end) through 1977; resistance should be 1.6-2.0-. In 1978, connect the ohmmeter to the coil terminals: resistance should be 0-. If more than 2.0-, 1976-77, or 1.8-, 1978, replace the coil.
- Disconnect the harness from the electronic control unit. Connect an ohmmeter to the red and the green wire terminals. Resistance should be 720-. If far more or far less, replace the distributor pick-up coil.
- Disconnect the anti-dieseling solenoid connector (see Driveability & Emissions Controls ). Connect a voltmeter to the red and green terminals of the electronic control harness. When the starter is cranked, the needle should deflect slightly. If not, replace the distributor pick-up coil.
- Reconnect the ignition coil and the electronic control unit. Leave the anti-dieseling solenoid wire disconnected. Unplug the high tension lead (coil-to-distributor) from the distributor and hold it 0.012-0.24 in. (3-6mm) from the cylinder head with a pair of insulated pliers and a heavy glove. BE CAREFUL! When the engine is cranked, a spark should be observed. If not, check the lead, and replace the electronic control unit.
Reconnect all wires.
1976-77: connect the voltmeter (+) lead to the blue electronic control harness connector and the (-) lead to the black wire. The harness should be attached to the control unit.
As soon as the ignition switch is turned ON , the meter should indicate battery voltage. If not, replace the electronic control unit.1979-80 Vehicles
- Make a check of the power supply circuit. Turn the ignition OFF . Disconnect the connector from the top of the IC unit. Turn the ignition ON . Measure the voltage at each terminal of the connector in turn by touching the probe of the positive lead of the voltmeter to one of the terminals, and touching the probe of the negative lead of the voltmeter to a ground, such as the engine. In each case, battery voltage should be indicated. If not, check all wiring, the ignition switch, and all connectors for breaks, corrosion, discontinuity, etc., and repair as necessary.
Check the primary windings of the ignition coil. Turn the ignition
. Disconnect the harness connector from the negative coil terminals. Use an ohmmeter to measure the resistance between the positive and negative terminals on the coil. If resistance is 0.84-1.02-, the coil is OK. Replace if far from this range.If the power supply, circuits, wiring, and coil are in good shape, check the IC unit and pick-up coil, as follows:
- Turn the ignition OFF .
- Remove the distributor cap and ignition rotor.
- Use an ohmmeter to measure the resistance between the two terminals of the pick-up coil, where they attach to the IC unit. Measure the resistance by reversing the polarity of the probes. If approximately 400- are indicated, the pick-up coil is OK, but the IC unit is bad and must be replaced. If other than 400- are measured, go to the next step.
- Be certain the 2-pin connector to the IC unit is secure. Turn the ignition ON . Measure the voltage at the ignition coil negative terminal. Turn the ignition OFF .
If zero voltage is indicated, the IC unit is bad and must be replaced. If battery voltage is indicated, proceed.1981-86 Vehicles
BATTERY VOLTAGE (NO LOAD)
With the ignition key in the OFF position, connect a voltmeter to the positive and negative terminals of the battery. The reading should not be below 11.5 volts. A lower reading indicates a faulty battery, charging or starting system.BATTERY CRANKING VOLTAGE
- Connect a voltmeter to the battery and set to the appropriate scale.
- Remove the coil wire from the distributor cap and ground it.
- Crank the engine for approximately 15 seconds. The voltage reading should not be less than 9.6 volts while cranking. A lower reading indicates a faulty battery, charging or starting system.
With the distributor cap removed, connect an ohmmeter to each end of the spark plug cables. The resistance readings should be less than 30,000-. If the resistance readings are greater than 30,000-, replace the distributor cap and/or plug wires.IGNITION COIL SECONDARY CIRCUIT
With the ignition key in the OFF position, and the coil wire removed from the coil, connect an ohmmeter with one probe to the coil wire socket and the other to the negative terminal. Check both coils. The resistance reading should be between 7,000-11,000-. If not, replace the ignition coil.POWER SUPPLY CIRCUIT
- Connect a voltmeter with the positive probe to the B terminal (power source) and the negative probe to the distributor housing.
- Turn the ignition key to the ON position.
- The reading should be between 11.5-12.5 volts. If below 11.5 volts, check the wiring between the ignition switch and the I.C. unit.
- Connect a voltmeter as in Step 1 above.
- Pull the coil wire from the distributor cap and ground it.
- Turn the key to the START position and observe the voltmeter while the engine is cranking.
- If the voltage reading is more than 1 volt below battery cranking voltage and/or is below 8.6 volts, check the ignition switch and wiring from the switch to the I.C. unit.
- Connect a voltmeter negative probe to the I terminal and the negative voltmeter probe to the distributor housing.
- Turn the ignition key to the ON position. If the reading is between 11.5-12.5 volts proceed to Step 3. If the reading is below 11.5 volts proceed to the Ignition Coil Primary Circuit test.
- Connect the voltmeter positive probe to the E terminal and the negative voltmeter probe the distributor housing.
- Turn the ignition key to the ON position. If the reading is between 11.5-12.5 volts proceed to the I.C. Unit Ground Circuit test. If the reading is below 11.5 volts proceed to the Ignition Coil Primary Circuit test.
- Place the ignition key in the OFF position.
- Remove the coil wire from the coil.
- Measure the resistance between the two terminals of the coil. The resistance should be between 1.04-1.27-. If not the ignition coil is defective and should be replaced.
- Connect the positive probe of a voltmeter to the housing of the distributor.
- Connect the negative probe of a voltmeter to the negative terminal of the battery.
- Pull out the coil wire from the distributor cap and ground it.
- Turn the key to the START position and observe the voltmeter while cranking.
- If the voltmeter reading is 0.05 volts or less, replace the IC ignition unit assembly.
- If the voltmeter reading is more than 0.5 volts, check the distributor ground, wiring from the chassis ground to the battery including battery cable connections.