Secondary Ignition Cable Insulation Test

CAUTION: Do not pull spark plug cables from distributor cap of four cylinder engines. The cables must be released from inside the distributor cap.

CAUTION: Do not leave any one spark plug cable disconnected any longer than necessary during testing. Excessive heat could damage the catalytic converter. Total test time must not exceed ten minutes.

CAUTION: To maintain proper sealing at the terminal connections, the connections should not be broken unless testing indicates high resistance, an open circuit or other damage.

INSPECTION
Check connections at the coil, distributor cap towers and spark plugs.
Terminals should be fully seated, and the nipples and spark plug covers should be in good condition.

Covers should fit tightly on the coil, distributor cap towers and spark plug insulators.

Cable connections that are loose will corrode and increase the resistance and permit water to enter the towers causing ignition malfunction.


INSULATION TEST

NOTE: When testing secondary cables for punctures and cracks with an oscilloscope follow the equipment manufacturers instructions. If an oscilloscope is not available, secondary cables can be tested as follows:

1. With the engine not running, connect one end of a test probe (i.e. a piece of wire with insulated alligator clips on each end) to a good ground, other end free for probing.

2. With engine running, move test probe along entire length of all cables (approximately 0 to 1/8 inch gap). If punctures or cracks are present there will be a noticeable spark jump from the faulty area to the probe. Check the coil cable the same way.

3. Replace ALL cracked, leaking or faulty cables.


RESISTANCE TEST
Use an ohmmeter to check resistance type cable for open circuits, loose terminals or high resistance as follows:

Remove cable from spark plug.

Lift distributor cap from distributor with cables intact. Do not remove cables from cap. The cables must be removed from the spark plugs.

Connect the ohmmeter between spark plug end terminal and the corresponding electrode inside the cap, make sure ohmmeter probes arc in good contact. Resistance should be within tolerance shown in the cable resistance chart. If resistance is not within tolerance, remove cable at cap tower and check the cable. If resistance is still not within tolerance, replace cable assembly. Test all spark plug cables in same manner.


To test coil to distributor cap high tension cable, remove distributor cap with the cable intact. Do not remove cable from the cap. Connect the ohmmeter between center contact in the cap and remove the cable at coil tower and check cable resistance. If resistance is not within tolerance, replace the cable. Also, check for a loose connection at the tower or for a faulty coil.

Inspect coil tower for cracks or carbon tracking.