Wiring Help Needed...

Discussion in '1965 - 1973 Classic Mustangs -General/Talk-' started by 408steve, Sep 23, 2013.

  1. Ok, first of all, when it comes to wiring, I am an idiot, and not much better in the diagnostic area either. Have a '69 that I acquired with a restomod partially completed. It has a 408 crate engine, and was running a Jacobs C4 coil and Pertronix Ignotor II billet distributor. The ignition is wired through a switch that energizes the Holley electric fuel pump and the ignition, but the starter circuit is still on the keyed switch. Starting a couple of weeks ago, the car ran poorly, then died. Diagnosing the coil revealed no voltage on the outlet side, so I replaced it with an MSD Blaster 2coil, and a new coil wire, but still won't start. Further investigation reveals 12V on the positive side of the coil with the ignition on, but also 12V on the negative side. Is this normal? Any help would be appreciated. I can wire a whole house with 120VAC, but this 12V stuff make me want to pull my hair out.
  2. Ignition coils work on saturation, positive side is continous 12volts.
    Neg side of coil is temporarily grounded,when ground circuit breaks
    A spark is created. So if 12 volts present on both sides of coil you have an open between coil and distributor ignition module. Possible pertronics igniter has gone bad. Tapping a ground jumper should fire the coil to test it. Just pull centre wire from distributor and place it near a bolt or something on engine. A spark shoul jump the gap. 1/8" to 1/4is enough of a gap to test.
  3. you coil question is one i always ask people, do they have voltage to the coil, and then do they have voltage through the coil. as noted, the reason for that is the coil has to build up a magnetic field that the system then collapses into the secondary windings to create a high voltage spark at the plug. so since you do have voltage through the coil my next suggestion is to check to see if you have a spark. pull the coil wire and holding it close to a ground, crank the engine with the key on and see if you get a nice blue spark or not. if not then you have a triggering issue, if so then you likely have a fuel issue.