Mazda 323/626/929/GLC/MX-6/RX-7 1978-1989

Ignition Coil

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CHECKING IGNITION COIL RESISTANCE



Except RX-7
1978-81 VEHICLES

See Figures 1 and 2

  1. Run the engine until it reaches operating temperature (coil must be hot). Disconnect the high tension lead from the coil tower.
  2.  
  3. Measure primary resistance with an ohmmeter, connecting between the coil's negative (-) and positive (+) primary terminals. Resistance should be 1.15-1.28 ohms (GLC) or 0.9-1.15 ohms (626).
  4.  
  5. Measure secondary resistance, connecting the ohmmeter between the coil tower and the positive (+) primary terminal. Resistance should be 13,500 ohms (GLC) or 7,000 ohms (626).
  6.  
  7. Replace the coil if either resistance is incorrect by more than 10%.
  8.  



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Fig. Fig. 1: Test the coil primary resistance as shown



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Fig. Fig. 2: Test the coil secondary resistance as shown

1982-89 VEHICLES

See Figures 3, 4 and 5

  1. Connect an ohmmeter, set to the x 1 scale, to the positive (+) and negative (-) primary terminals of the coil. The coil should have good continuity; resistance should be approximately 1.0-1.3 ohms on all models except the 1988-89 626/MX-6 turbo and 929. Resistance on the 1988-89 626/MX-6 turbo and 929 should be 0.72-0.88 ohms.
  2.  



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Fig. Fig. 3: Checking ignition coil primary resistance-1986-89 323, 626/MX-6 and 929

  1. Disconnect the high tension wire from the coil. Connect the ohmmeter to the positive (+) coil terminal and the metallic connector inside the coil tower. Set the ohmmeter to the x 1000 scale. Resistance must be 10,000-30,000 ohms, except on the following:

    1986-89 323: 6,000-30,000 ohms
     
    1988-89 626/MX-6 (non-turbo): 7,000-9,700 ohms
     
    1988-89 626/MX-6 (turbo): 10,300-13,900 ohms
     

  2.  



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Fig. Fig. 4: Checking ignition coil secondary resistance-1986-89 323, 626/MX-6 and 929



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Fig. Fig. 5: Checking ignition coil insulation-1986-89 323, 626/MX-6 and 929

  1. You can also check for bad coil insulation by measuring the resistance between the coil negative (-) primary connection and the metal body (housing) of the coil. If resistance is less than 10,000 ohms, replace the coil.
  2.  

This test may not be entirely satisfactory unless you have a tester that produces 500 volts. If the tests below do not reveal the problem and, especially, if operating the engine at night produces some bluish sparks around the coil, you may want to remove the coil and have it tested at a diagnostic center.

  1. If the coil resistances are not as specified, replace the coil.
  2.  
  3. If the coil tests OK, replace the igniter and pickup coil. However, you should make sure before doing this work that there are no basic maintenance problems in the secondary circuit of the system, since it is often impossible to return electrical parts. We suggest that before you replace the igniter and pickup coil, you carefully inspect the cap and rotor for carbon tracks or cracks. Also, disconnect the wires and measure their resistance with an ohmmeter. Resistance should be 16,000 ohms per length of 3.28 feet (1 meter). Also, check for cracks in the insulation. Replace secondary parts as inspection/testing deems necessary before replacing the igniter and pickup coil.
  4.  

RX-7
1979-85 VEHICLES

The coil(s) must be at normal operating temperature to perform this test, so either start the engine or turn the ignition ON until the coils heat up. If one or both coils won't get hot, check your wiring or try to substitute coil(s).

  1. Check the leading ignition first. Remove the high tension cable from its center tower and connect the leads of an ohmmeter to the two side terminals. Resistance should be 1.22-1.48 ohms.
  2.  
  3. Test the trailing coil in the same manner. It should also give a reading of 1.22-1.48 ohms.
  4.  
  5. If either reading is out of specification, replace the coil(s).
  6.  

1986-89 VEHICLES

See Figures 6 and 7

This testing procedure covers both the leading and trailing side ignition coils; however, the coils differ in appearance and design. On the trailing side coil, there are two sets of terminals that require resistance checks, whereas the leading side has only one set. When checking the coil resistance, be sure to distinguish between the two coils.



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Fig. Fig. 6: Checking the leading ignition coil resistance-1986-89 RX-7



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Fig. Fig. 7: Checking the trailing ignition coil resistance-1986-89 RX-7. Note the two sets of terminals to be checked

  1. Disconnect the negative battery cable.
  2.  
  3. Set your ohmmeter to the x 1 scale, then connect the ohmmeter probes to the positive (+) and negative (-) coil terminals. On the trailing side, test both sets of terminals.
  4.  
  5. If the resistance is above 1 ohm, replace the coil.
  6.  

CHECKING EXTERNAL RESISTOR



1979 RX-7 Only

See Figure 8

The external resistor block is located inside the engine compartment on the driver's side strut pod. The external resistor modifies the current going into the positive primary terminal of the ignition coil. This allows the coil to be constructed so that a strong spark is generated at high engine speeds.

All of the electrical terminals for the trailing ignition coil have light colored protective caps, while all leading coil terminals have dark colored caps.

Connect the leads of an ohmmeter to the trailing coil side of the resistor (the side with the light colored caps). Resistance should be 1.26-1.54 ohms. Repeat the test on the leading side of the resistor (the side with dark caps). The reading should be the same as for the trailing side. If the reading is not within or close to this range, replace the resistor.



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Fig. Fig. 8: Checking the external resistor (left) and the leading ignition coil's primary resistance (right)-1979 RX-7

REMOVAL & INSTALLATION



Except RX-7

Most Mazda coils are located on the fender well (rear wheel drive cars) or the front engine compartment panel (front wheel drive cars) to keep them away from engine heat. On some 1986-89 models, the ignition coil is bolted to the air cleaner assembly.

  1. Disconnect the negative battery cable and make sure the ignition switch is OFF .
  2.  
  3. Remove the protective boot from the top of the coil, if necessary, by sliding it back on the coil-to-distributor wire.
  4.  
  5. Carefully pull the high tension wire out of the coil, twisting it gently as near as possible to the tower to get it started.
  6.  
  7. Note the routing and colors of the primary wires, then remove the nuts and lockwashers, retaining all parts for installation. Clean the primary terminals with fine grit sandpaper, if necessary, to ensure a clean connection. Then, loosen the through-bolt or bolts which clamp the coil in place and slide the coil out of its mount.
  8.  

To install:
  1. Install the new coil in exact reverse order, making sure the primary (+ and -) connections are clean and tight. Ensure also that the coil-to-distributor wire is fully seated in the tower and that the protective boot is fully installed on the outside of the tower.
  2.  

RX-7-1979-85
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the negative (-) coil terminal couplers.
  4.  
  5. Loosen the nuts on the positive (+) terminals and remove the wires.
  6.  
  7. Label, then remove, the wires from the leading and trailing coils.
  8.  
  9. Remove the three bracket bolts and coil assembly.
  10.  

To install:
  1. Position the new coil assembly onto its mounting and attach it with the three bracket bolts.
  2.  
  3. Connect the wires to the leading and trailing coils.
  4.  
  5. Place the wires on the positive (+) coil terminals and install the terminal post nuts.
  6.  
  7. Connect the negative (-) terminal couplers.
  8.  
  9. Connect the negative battery cable.
  10.  

RX-7-1986-89

The 1986-89 RX-7 leading and trailing ignition coils each have a built-in igniter.

LEADING SIDE
  1. Disconnect the negative battery cable.
  2.  
  3. Label the wires for identification.
  4.  
  5. Loosen the nuts and disconnect the primary wires from the coil/igniter.
  6.  
  7. Disconnect the 2-prong connector.
  8.  
  9. Remove the bracket bolts and coil/igniter assembly.
  10.  
  11. Installation is the reverse of removal.
  12.  

TRAILING SIDE
  1. Disconnect the negative battery cable.
  2.  
  3. Label the wires for identification.
  4.  
  5. Loosen the nuts and disconnect the (B) and (L) primary wires from the coil/igniter.
  6.  
  7. Disconnect the 2 and 4-prong connectors.
  8.  
  9. Remove the bracket bolts and coil assembly.
  10.  
  11. Installation is the reverse of removal.
  12.  

 
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