bad. spark

[Mr. Jones]

Engine runs poorly,checked spark out the coil wire.Red and no white,no blue.What's that mean bad coil or a bad wire somewhere???

[daleshotrodshop]

Probably not the coil. Most likely a bad ground wire from distributor to breaker plate, you can check with ohm meter between breaker plate and distributor or just a visual. Also rust or oil between points and breaker plate can cause this, also check this for the condenser mounting.. Also check points for any pitting or burning. Check voltage to coil during crank for full voltage, also check coil wire for low resistance. I would also make sure you have a good engine ground.
I have a section from a 1964 F series Ford service manual that covers this well on my website at http://fasthotrods.com/technical-information/cat_view/118-ignition/120-ford.html

[64 f100]

Several possible places I would suspect. First, check voltage coming from ignition wiring. Coils are 6 volt and there is built in resistance to drop voltage going to coil to about 8 volts. Actually, first check for bad grounds then start on other things. To continue, to much voltage going to the coil will cause it to overheat and damage it. Condensers are really a kind of capacitor and do go bad just setting around. These do not have unlimited shelf life and will go bad setting around for very long lengths of time. Checking a coil used to be done on an oscilloscope. The line it makes should be a long cone shape, if it is short or dies out fast, then it is bad. However, as long as the spark jumps at least a quarter inch, then it should run. I would also check the play in the distributer shaft, which will adversely affect the engines running, as the dwell on the points will vary. Personally, I throw away points now days and go directly to Petronix igniter. Also a Petronix coil is a good investment, higher fire and better fuel economy. You should check your timing chain for slack and play also. Easy enough to do. Take the cap off the distributor and watch the rotor as you manually rotate the crank back and forth with a break over bar and socket. Slack will be determined by how much you turn the crank before the distributer rotor turns.

rich