Hey guys,
I'm working on My 85 Bronco that has a 383 windsor based stroker in it. I have a Mallory ignition system (Promaster Coil and Unilite Distributor) and I cant get a Spark. I have Power at the coil on both sides (8 volts) and i just replaced the coil, the cap and rotor and the ignition module in the distributor. What else can cause me to not have spark?
here is a link to what the wiring looks like.

http://www.google.com/imgres?q=mallo...:0&tx=30&ty=71
Any help is appreciated. thanks

 

I also replaced all of the spark plugs and wires recently. And I replaced the ballast resistor when i replaced the coil

 

Do you have regular versions of a distributor and coil to try? Replace the Mallory pieces one at a time to see if you get any response.

 

I got the truck with all of the mallory parts already in it. It ran fine until about a week ago when one day i tried to start it and had no spark. I have since replaced all of the old mallory components with new mallory components.

 

So both the old and new Mallory components are not generating a spark? That does seem very strange.

When the ignition is under normal operation, the coil gets its current through the ballast resistor, so about 9 volts are applied to the primary. Usually when you're starting the engine, the starter switch shorts out the ballast resistor to provide full 12V to the coil. This gives a stronger spark to help the engine start easier.

The event that triggers the spark is either the contact points open or the opto-electronics in the Unilite interrupts the current flowing through the coil, causing a collapse of its magnetic field, that generates the high voltage on the secondary. So if you're measuring 8v on both sides of the coil, that means it is being adequately charged. But not getting a spark means the triggering event is not happening. That would be pointing to the Unilite circuit in the distributor.

Ironically, a conventional distributor with points and condenser can be much more reliable than an electronic distributor, like the Unilite or a magnetically triggered version like Ford's Duraspark. All the electronic versions have a lot of active components that can fail. The contact points can wear out, but unless it physically breaks, it doesn't really fail.

 

Turned out to be the mallory ignition module all along. I replaced the cap and rotor before i replaced the ignition module, and today as i was looking stuff over i realized that the new Rotor was a little different than my old one and didn't go down far enough into the distributor to interrupt the infra red light in the module. put the contacts from the new rotor on the old one and she fired right up.
Thanks for the help.