Mazda Trucks 1987-1993 Repair Guide

Spark Plug Wires



See Figure 1

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Fig. Fig. 1: Checking individual plug wire resistance with a digital ohmmeter

At every tune-up/inspection, visually check the spark plug cables for burns, cuts, or breaks in the insulation. Check the boots and the nipples on the distributor cap and/or coil. Replace any damaged wiring.

Whenever a high tension wire is removed for any reason from a spark plug, coil or distributor terminal housing, silicone grease should be applied to the boot before it is reconnected.

Every 50,000 miles (80,000 Km) or 60 months, the resistance of the wires should be checked using an ohmmeter. Wires with excessive resistance will cause misfiring, and may make the engine difficult to start in damp weather. Resistance should measure as follows:

Pickups and MPV-16k ohms per 3.28 feet (1m) of wire
Navajo-7k ohms per foot (30cm) of wire

It's a good idea to replace the wires in sets, rather than individually. The wires should also be tested for resistance with an ohmmeter.

Only test one spark plug wire at a time. When the check is complete return the plug wire to its original location. If the wire is defective and more wires are to be checked, mark the wire as such, return it to its original location, then inspect the other wires. Once all of the wires are checked, replace the defective wires one at a time. This will avoid any mix-ups.


See Figures 2 and 3

When removing spark plug wires, use great care. Grasp and twist the insulator back and forth on the spark plug to free the insulator. Do not pull on the wire directly as it may become separated from the connector inside the insulator.