Nissan Z - ZX 1970-1988 Repair Guide

Non-Turbocharged Engines

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See Figures 1, 2, 3 and 4

All 1974 and later vehicles are equipped with electronic ignition as standard equipment. The 1974 models (with an automatic transmission), plus the 1975-76 49 States and Canadian models have two pick-ups in the distributor. All 1975-76 California models, plus all 1977 and later models have only one pick-up.

The 1974 system has a different electronic module than later systems, which precludes troubleshooting of the system by the home mechanic. However, the pick-up air gap adjustments and ignition timing adjustments can be performed in the same manner as for the 1975-78 models. The 1978 system differs slightly from the 1975-77 system; the 1979 and later electronic ignition is markedly different, although the operating principle is the same.

The electronic ignition differs from its conventional counterpart only in the distributor component area. The secondary side of the ignition system is the same as a conventional breaker points system.



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Fig. Fig. 1: Measure the reluctor air gap with a non-magnetic feeler gauge



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Fig. Fig. 2: Exploded view of a 1975-78 electronic distributor



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Fig. Fig. 3: Exploded view of a 1979-83 electronic distributor



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Fig. Fig. 4: Electronic distributor-1984-88 models

Located in the distributor, in addition to the normal ignition rotor, is a six-spoke rotor (reluctor) which rests on the distributor shaft where the breaker point's cam is found on earlier systems. A pick-up coil, consisting of a magnet, a coil and wiring, rests on the breaker plate next to the reluctor. The system also uses a transistorized ignition unit, located on the right side of the firewall in the passenger compartment (1970-78). The 1979-83 models have an integrated circuit (IC) ignition unit, which is mounted on the side of the distributor. In addition, 1979-83 models use a ring type pick-up coil, which surrounds the reluctor, rather than the arm type coil used on the 1970-78 models.

When a reluctor spoke is not aligned with the pick-up coil, it generates large lines of flux between itself, the magnet and the pick-up coil. This large flux variation generates a high voltage in the pick-up coil, preventing the current from flowing to the pick-up coil. When a reluctor spoke lines up with the pick-up coil, the flux variation is low, thus, zero voltage is generated, allowing current to flow to the pick-up coil. Ignition primary current is then cut off by the electronic unit, allowing the field in the ignition coil to collapse, inducing high secondary voltage in the conventional manner. The high voltage then flows through the distributor to the spark plug, as usual.

Because no points or condenser are used and the dwell is determined by the electronic unit, no adjustments are necessary. The ignition timing is checked in the usual way, but unless the distributor is disturbed it is not likely to ever change very much.

Service consists of inspection of the distributor cap, the rotor and the ignition wires, and replacing them (when necessary). These parts can be expected to last for at least 40,000 miles (64,000 km). In addition, the reluctor air gap should be checked periodically.

INSPECTION



  1. The distributor cap is held on by two clips. Release them with a screwdriver, then lift the cap straight up and off, with the wires attached. Inspect the cap for cracks, carbon tracks or a worn center contact. Replace it (if necessary), transferring the wires (one at a time) from the old cap to the new one.
  2.  
  3. Pull the ignition rotor (not the spoked reluctor) straight up to remove it. Check the reluctor air gap. Refer to the next step. Replace it if its contacts are worn, burned or pitted, DO NOT file the contacts.
  4.  
  5. Before replacing the ignition rotor, check the reluctor air gap. Use a non-magnetic feeler gauge. Rotate the engine until a reluctor spoke is aligned with the pick-up coil (either bump the engine around with the starter or turn it using a wrench on the crankshaft pulley bolt). The gap should measure 0.3-0.4mm for 1974, 0.2-0.4mm for 1975-78 or 0.3-0.5mm for 1979-83 models. Adjustment (if necessary) is made on 1974-78 models by loosening the pick-up coil mounting screws and shifting its position on the breaker plate either closer to or farther from the reluctor. On the 1979-83 models, center the pick-up coil (toothed stator ring) around the reluctor. Tighten the screws and recheck the gap.
  6.  
  7. Install the rotor by pressing it firmly onto the distributor shaft. It will fit in only one way, so be sure it is fully seated.
  8.  
  9. Inspect the ignition wires for cracks or brittleness. Replace them one at a time to prevent cross-wiring, carefully pressing the replacement wires into place. The cores of wires used with electronic ignition are more susceptible to breakage than those of standard wires, so treat them gently.
  10.  

TROUBLESHOOTING



1974 Models

The 1974 electronic ignition cannot be tested using conventional equipment. It must be checked by a dealer with a Datsun/Nissan-made transistor ignition unit tester. The only alternative available to the home mechanic is a substitution test of the control unit. If a unit known to be good operates correctly in the vehicle, the old unit is presumably faulty. This method is far from satisfactory; it ignores all of the associated systems and can result in a protracted and needless waste of money and time. It is strongly recommended that problems with the 1974 ignition system be referred to your dealer.

1975-78 Models

See Figures 5, 6, 7, 8 and 9

The components used in these systems are basically similar. However, differences exist, which affect the troubleshooting process.

There were two different systems used in 1975 and 1976. One is for Z-cars sold in California, which have one pick-up in the distributor. The wiring harness to the module is composed of six wires: one black (B), two black with white stripe (BW), one blue (L), one red (R) and one green (G). The 49 States and Canadian models have seven wires in the harness: black (B), black with white stripe (BW), white (W), blue (L), red (R), green (G) and brown (Br). The 1977 system is the same as the 1975-76 California system.



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Fig. Fig. 5: Electronic distributor control module-1975-76 49 state version



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Fig. Fig. 6: Electronic distributor control module-1975-76 California models and all 1977 models



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Fig. Fig. 7: Electronic distributor control module-1978 models



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Fig. Fig. 8: Checking the power supply at the harness-1975-76 49 state version



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Fig. Fig. 9: Checking the power supply at the harness-1975-76 California models and all 1977 models

The main differences between the 1975-77 and the 1978 systems are:

  1. The 1975-77 system uses an external ballast resistor located next to the ignition coil.
  2.  
  3. The earlier system uses a wiring harness with individual eyelet connectors to the electronic unit, while the later system uses a multiple plug connector.
  4.  

You will need an accurate voltmeter and ohmmeter for these tests, which must be performed in the order given:

  1. Check all connections for corrosion, looseness, breaks and etc., then correct, if necessary. Clean and gap the spark plugs.
  2.  
  3. Disconnect the harness (connector or plug) from the electronic unit. Turn the ignition switch ON . Set the voltmeter to the 50v, DC range. Connect the positive (+) voltmeter lead to the black/white wire terminal and the negative (-) lead to the black wire terminal. On the 1975-76 California models and all 1977 models, you will have to perform this test twice, first at one black/white wire and then the other. Battery voltage should be detected; if not, check the black/white and black wires for continuity, the battery terminals for corrosion and the battery state of charge.
  4.  
  5. Connect the voltmeter positive lead to the blue wire and the negative lead to the black wire. Battery voltage should be detected; if not, check the blue wire for continuity, the ignition coil terminals for corrosion or looseness and the coil for continuity. On the 1975-77 models, check the external ballast resistor connections.
  6.  
  7. On the 1975-77 models, disconnect the distributor harness wires from the ignition coil ballast resistor, leaving the ballast resistor-to-coil wires attached. On the 1978 models, disconnect the ignition coil wires. On the 1975-77 models, connect the leads of an ohmmeter to the ballast resistor outside terminals (at each end): resistance should be 1.6-1.8 ohms for 1975 models or 1.6-2.0 ohms for 1976-77 models. On 1978 models, connect the ohmmeter to the coil primary terminals: the resistance should be 0. If resistance is more than 1.8 ohms (1975), 2.0 ohms (1976-77) or 1.8 ohms (1978), replace the coil.
  8.  
  9. Disconnect the harness from the electronic control unit. Connect an ohmmeter to the red and green wire terminals; the resistance should be 720 ohms. If far more or far less, replace the distributor pick-up coil (retarded side pick-up coil on 1975-76, 49 States and Canadian models).
  10.  

The following step is ONLY for 1975-76, 49 States and Canadian models with two pick-up coils in the distributor. Skip this step if your vehicle has only one pick-up coil.

  1. Disconnect the brown wire from the control unit. Connect an ohmmeter between the brown and green wire terminals. The resistance should be approximately 720 ohms. If far more or far less, replace the advance side pick-up coil in the distributor.
  2.  
  3. Turn OFF the ignition. Disconnect the fuel injection wiring harness from the cold start valve. Connect a voltmeter to the red and green terminals of the electronic control harness. When the starter is cranked, the needle of the voltmeter should deflect slightly; if not, replace the distributor pick-up coil. (This would be the retarded side coil, on models with two pick-up coils.) Repeat the test between the brown and green terminals to check the advance side pick-up coil (1975-76: 49 States and Canada models ONLY).
  4.  
  5. Reconnect the ignition coil and the electronic control unit harness. Disconnect the fuel injection wiring harness from the injectors and the cold start valve. Unplug the high tension lead (coil-to-distributor) from the distributor and hold it 0.13-0.25 in. (0.3-0.010mm) from the cylinder head with a pair of insulated pliers and a heavy glove. When the engine is cranked, a spark should be observed. If not, check the lead and replace (if necessary). If still no spark, replace the electronic control unit.
  6.  


WARNING
DO NOT make this test near the fuel injection wiring harness. Damage to the fuel injection control unit will result, if sparks travel to the harness.

  1. Reconnect all of the wires as follows:
    1. On the 1975-77 models: connect the voltmeter positive lead to the blue control unit wire terminal and the negative lead to the black wire terminal. The harness should be attached to the control unit.
    2.  
    3. On the 1978 models: connect the voltmeter positive lead to the negative terminal of the ignition coil and the negative lead to a good ground.
    4.  

  2.  
  3. As soon as the ignition switch is turned ON , the meter should indicate battery voltage. If not, replace the electronic control unit.
  4.  

1979-83 Models

See Figures 10 and 11

  1. Turn the ignition switch OFF . Disconnect the fusible link connector for the fuel injection wiring harness. Be sure the ignition is OFF before doing this. Disconnect the cold start valve wiring harness connector. Disconnect the high tension lead (coil-to-distributor) at the distributor and hold it 0.13-0.25 in. (3.3-6.3mm) away from the cylinder head with a pair of insulated pliers and a heavy glove. When the engine is cranked, a spark should be observed. If not, check the lead and replace as necessary. If there is still no spark, go on with the following system checks.
    1. Make a check of the power supply circuit. Turn the ignition OFF . Detach 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 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 of the wiring, the ignition switch and all connectors for breaks, corrosion, discontinuity etc., then repair as necessary
    2.  
    3. Check the primary windings of the ignition coil. Turn the ignition OFF . Detach the harness connector from the negative coil terminal. Use an ohmmeter to measure the resistance between the positive and negative coil terminals. If resistance is 0.84-1.02 ohms, the coil is OK; replace it if the reading is far from this range.
    4.  

  2.  
  3. If the power supply, circuits, wiring and coil are in good shape, check the IC unit and pick-up coil as follows:
    1. Turn the ignition OFF .
    2.  
    3. Remove the distributor cap and ignition rotor.
    4.  
    5. Using an ohmmeter, 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 ohms are indicated, the pick-up coil is OK, but the IC unit is bad and must be replaced.
    6.  

  4.  



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Fig. Fig. 10: Connect the ohmmeter to the pick-up coil terminals-1979-83 models



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Fig. Fig. 11: Remove the screws (arrows) to detach the IC unit-1979-83 models

  1. If the resistance is other than 400 ohms, proceed with the following:
    1. Be certain the two pin connector to the IC unit is secure.
    2.  
    3. Turn the ignition ON .
    4.  
    5. Measure the voltage at the ignition coil's negative terminal.
    6.  
    7. Turn the ignition OFF .
    8.  

  2.  


WARNING
Remove the tester probe from the coil negative terminal before switching the ignition OFF, to prevent burning out the tester.

    1. If 0 voltage is indicated, the IC unit is bad and must be replaced.
    2.  


  1. If battery voltage is indicated, remove the IC unit from the distributor, by proceeding as follows:
    1. Disconnect the battery ground (negative) cable.
    2.  
    3. Remove the distributor cap and ignition rotor.
    4.  
    5. Disconnect the harness connector from the top of the IC unit.
    6.  
    7. Remove the two screws securing the IC unit to the distributor.
    8.  
    9. Disconnect the two pick-up coil wires from the IC unit.
    10.  

  2.  


WARNING
Pull the connectors free with a pair of needlenose pliers. DO NOT pull on the wires to detach the connectors.

    1. Remove the IC unit.
    2.  


  1. Measure the resistance between the terminals of the pick-up coil. It should be approximately 400 ohms. If so, the pick-up coil is OK and the IC unit is bad. If the resistance is other than 400 ohms, the pick-up coil is bad and must be replaced.
  2.  

1984-88 Models

The 1984-88 and later distributors are checked by replacement ONLY.

PICK-UP COIL AND RELUCTOR REPLACEMENT



1974-78 Models

The reluctor cannot be removed on some early 1974 models; it is an integral part of the distributor shaft. Non-removable reluctors can be distinguished by the absence of a roll pin (retaining pin) which locks the reluctor in place on the shaft.

PICK-UP COIL

See Figure 12

  1. Remove the distributor cap by releasing the two spring clips. Remove the ignition rotor by pulling it straight up and off the shaft.
  2.  
  3. Disconnect the distributor wiring harness at the terminal block.
  4.  
  5. Remove the pick-up coil mounting screws and the screws retaining the wiring harness to the distributor.
  6.  
  7. Remove the pick-up coil.
  8.  



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Fig. Fig. 12: Remove the pick-up coil-1974-78 models

  1. To replace the pick-up coil, reverse the removal procedures but, leave the mounting screws slightly loose to facilitate air gap adjustment.
  2.  

RELUCTOR WITH ROLL PIN

See Figure 13

  1. Remove the distributor cap, ignition rotor and the pick-up coil.
  2.  
  3. Using two small prytools, pry the reluctor from the distributor shaft. Be extremely careful not to damage the reluctor teeth. Remove the roll pin.
  4.  



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Fig. Fig. 13: Correct roll pin installation-1974-78 models

  1. To replace, press the reluctor firmly onto the shaft. Install a new roll pin with the slit facing away from the distributor shaft. DO NOT reuse the old roll pin.
  2.  

1979-83 Models

See Figures 14 and 15

  1. Remove the distributor cap (release the spring clips) and the ignition rotor (pull straight up and off the shaft).
  2.  
  3. Using a pair of needlenose pliers, disconnect the pick-up coil spade connectors from the ignition unit. DO NOT pull on the pick-up coil wires.
  4.  



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Fig. Fig. 14: Remove the pick-up coil connectors



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Fig. Fig. 15: Correct roll pin installation-1979-83 models

  1. Remove the toothed stator and the ring magnet (from underneath) by removing the mounting screws.
  2.  
  3. Using two small prytools, pry the reluctor from the distributor shaft. Be careful not to damage the reluctor teeth. Remove the roll pin.
  4.  
  5. Remove the pick-up coil wiring harness-to-distributor retaining screw and the pick-up coil.
  6.  
  7. To install, reverse the removal procedures. Press the reluctor firmly into place on the shaft. Install a new roll pin with the slit in the pin parallel to the flat on the shaft. Install the magnet and stator, then center the stator around the reluctor; the air gap is 0.01-0.02 in. (0.3-0.4mm). Press the pick-up coil spade connectors onto the ignition unit terminals with your fingers. The proper connections can be determined from the color code marked on the grommet.
  8.  

 
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