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

Spark Plug Wires



See Figure 1

Visually inspect the spark plug cables for burns, cuts, or breaks in the insulation. Check the spark plug boots and the nipples on the distributor cap and coil. Replace any damaged wiring. If no physical damage is obvious, the wires can be checked with an ohmmeter for excessive resistance. Remove the first wire from the spark plug and the distributor cap, and connect one of the leads from the ohmmeter to each end of the wire. Factory recommendations are that resistance should not exceed 22,400 ohms per 39.37 in. (1 meter) of cable. The factory preferred resistance per 39.37 in. (1 meter) is 16,000 ohms.


When installing a new set of spark plug cables, replace the cables one at a time so there will be no mix-up. Start by replacing the longest cable first. Install the boot firmly over the spark plug. Route the wire exactly as the original was routed. Insert the nipple firmly into the tower on the distributor cap. Repeat the process for each cable, including the one which runs from the center of the distributor cap to the ignition coil. (On the RX-7, there are two ignition coil cables running to the distributor cap.)

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Fig. Fig. 1: Checking spark plug cable resistance with an ohmmeter