Intermittent Problem - Loss of Spark??

[chris belyea]

What should be the resistance of a plug wire?

[edmayo]

The original plug wire had zero resistance, it was copper stranded wire. All the resistance was in the plug connector and sometimes additional resistors in the distributor cap. This way resistance would always be the same no matter the wire length.

[sithot]

The original plug wire had zero resistance, it was copper stranded wire. All the resistance was in the plug connector and sometimes additional resistors in the distributor cap. This way resistance would always be the same no matter the wire length.

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Never doubt Ed Mayo.

[chris belyea]

So I've been problem shooting this for a little over a month now and still have no spark. I sent the CDI box and had it looked at and it checked out okay. Purchased a new coil; still no spark. I confirmed that I have power to the CDI box with the ignition on and when cranking. I'm going to run a few more test this weekend to see if I can find a solution but one thing that I found is that when I was checking power to the CDI box when starting, my multi meter indicated that the voltage was around 10.7v. Now I had long jumpers on things as I was alone and needed a way of cranking the car and reading the meter. How sensitive are these CDI boxes to voltage drop? Could my batteries have enough amperage to crank the car but not enough to generate spark?

Chris

[62S-R-S]

..I'm going to run a few more test this weekend to see if I can find a solution but one thing that I found is that when I was checking power to the CDI box when starting, my multi meter indicated that the voltage was around 10.7v.

Check as many crimped terminal ends that serve the ignition as you can, including all ground wires, inspect soldered joints, clean chassis ground points. Emory paper distributor shaft, check resistance of rotor, from tip to the shaft. Check total resistance of main ground cable to the battery.

[edmayo]

Take off the distributor cap, turn the engine by a wrench on the alternator nut until the points are closed, take the coil wire out of the center of the distributor cap and wedge it in the coil clamp so that the end is about an 1/8th" from touching ground. Now turn on the ignition, using a screwdriver push against the movable point arm, each time you break the connection you should see a spark jump to ground from the coil wire. Check the battery voltage directly at the battery terminals, should be about 12. 5 volts. If so use the voltmeter to check the voltage at the center pin of the three pin plug going to the C.D. box, should be same as battery voltage minus a couple tenths.