How to detect malfunction of the ignition wires

Checking the component, start with visual inspection. Check wires' insulation (with ignition off). The joints and bends of the wires should not have any damage (cracks, scorch marks or holes).

Next, make sure there is no rust between the ignition coil and the wire terminals.

If no damage has been found, determine the degree of resistance. To do so, use a multimeter. Connect probes of the measuring device to both ends of the wire. The normal resistance is 3.5 to 10 kOhm. If the difference of wires' resistance within the same set exceeds 4 kOhm, the wires are to be replaced.

Next check the operation of the ignition wires with the engine started. Be careful as the ignition wires are under high voltage. If clicking sounds produced by electric current are heard, or there are sparks, the ignition wires are to be replaced. Ignition wires should be diagnosed no less than once in 3 months.

You may notice that ignition wires require diagnostics by the following symptoms:

• Unstable idling of the engine, malfunctions;
• No ignition;
• The engine misses strokes at high RPM;
• The engine misfires;
• Increased fuel consumption;
• Failures of the electronic devices;
• Radio interference;
• Troubled ignition;
• Check Engine indicator activates on the dashboard;
• High CO2 content in exhaust gas.

The reasons for ignition wires malfunction

Terminals oxidation is the result of exposure to moisture. This occurs due to the loss of tightness in the protective cap during operation or installation.

Open electric circuit occurs due to insecure connection with the terminals of the elements of the ignition system, or due to damaged electric conductors. This may also occur during dismantling of the ignition wires. The damaged point gets heated and produces sparks, which results in burning out of the electric conductor and metal terminals.

The reason of current leakage may consist in damaged insulation or protective caps of the ignition wire. The quality of the insulation material is crucially important, as the service life of the component depends on it greatly. Even microcracks may be the reason of weak current. The insulation layer gets damaged due to exposure to high or low temperatures, and to chemicals. Sometimes, the ignition wire sheath wears out due to constant contact with some component.

Replacing ignition wires

Damaged ignition wires are only to be replaced. The ignition wires should only be replaced with ignition off, and the engine cooled down. During the installation of a new set, order of wires connection should be reproduced exactly. Therefore, the best practice is disconnecting and connecting the wires one by one.