Mazda Trucks 1972-1986 Repair Guide



You will need an accurate ohmmeter, a jumper wire and a 3.4 watt test light. Before proceeding with troubleshooting, make sure that all connections are tight and all wiring is intact.

  1. Check for spark at the coil high tension lead by removing the lead from the distributor cap and holding it about 1 / 4 in. from the engine block or other good ground. Use a heavy rubber glove or non-conductive clamp, such as a fuse puller or clothes pin, to hold the wire. Crank the engine and check for spark. If a good spark is noted, check the cap and rotor; if the spark is weak or nonexistent, replace the high tension lead, clean and tighten the connections and retest. If a weak spark is still noted, proceed to step 2.
  3. Check the coil primary resistance. Connect an ohmmeter across the coil primary terminals and check resistance on the low scale. Resistance should be 0.81-0.98 omega @ 70ºF (21ºC). If not, replace the coil.
  5. Check the coil secondary resistance. Connect an ohmmeter across the distributor side of the coil and the coil center tower. Read resistance on the high scale. Resistance should be 6,800-9,200 omega @ 70ºF (21ºC). If resistance is much higher (30,000-40,000 omega ), replace the coil.
  7. Next, remove the distributor cap and rotor. Crank the engine until a spoke on the rotor is aligned with the pick-up coil contact. Use a flat feeler gauge to check the gap. Gap should be 0.20-0.60mm. If not, gently bend the pick-up coil contact to correct the adjustment on 1979 models. On 1980 and later models, the gap is not adjustable. On these models, gap is corrected by parts replacement.
  9. Using an ohmmeter, check the pick-up coil resistance. Disconnect the 2-wire (red and green) connector at the distributor. The ignition switch should be in the OFF position. Insert the probes of the ohmmeter in the pick-up coil side of the connector. Resistance should be 760-840 omega for 1979 models, or 1,050 omega +- 10% for 1980 and later models. If not, replace the pick-up coil.
  11. Finally, test the ignition module. On 1979 models, connect the test light between the positive and negative terminal of the ignition coil. Connect a jumper wire between the positive coil terminal and the red wire of the pick-up coil, at the connector that you unplugged in the previous test. Be sure that you are attaching the wire to the pick-up coil side of the connector. Turn the ignition switch ON. The test light should light. Disconnect the jumper wire from the connector. The light should go out. If not, replace the module.

On 1980 and later models, the only way to test the module is to substitute a known good module in its place.


Unplug the primary ignition wire connector and connect an ohmmeter across the two prongs of the pick-up coil connector. Resistance, at 68ºF (20ºC), should be 800 omega +- 80 omega for 1979 models, 1,050 omega +- 105 omega for 1980 and later models.