I have the 8.5 mm Jacobs spark plug wires. I think I have one with a problem. What is the rule of thumb for measuring resistance to see if you have one gone bad? Is there a better way of testing? Is there a chart of resistance for different lengths of wire? I put the stock Motorcraft wire in place of the one I think is bad and I *think* it runs better. [img]images/icons/frown.gif[/img]
Whenever an engine feels like it's missing, just shut 'er down and start pulling plug wires one-by-one (starting it up after each pull). If it runs worse, the wire/sparkplug/cap terminal are good. If it runs the same, you've found the bad spot.
Well, I called them. They say it is 350 ohms per foot. I can always take one the same length that is believed to be good and measure it, I guess. Now I discovered that I need new batteries in my ohm meter.
I put new batteries in the multimeter, zeroed the ohms and checked it against a new 1.5K resistor. It read 1.503. So far so good. 6 of 8 of the Jacobs wires read over the 350 ohms per foot in a range of +5 to +685 most were +30 or a 3% variation. Is anything over the 350 per foot acceptable?