Ok, it's a 460 with electronic ignition. New coil, wires dist. cap/rotor. It won't start, has very little spark. After you crank it over and the motor stops turning it'll backfire. Real wierd. The motor is stopped and it tries to fire. Can I put 12 volts right from the battery to the coil without blowing the electronic ignition box up. Also, how do you test for a bad coil? The truck runs sometimes and sometimes it doesn't. It's my boss's truck and maybe if I can figure this out for him, he might not make me take out the trash. I really hate taking out the trash. Dumpsters suck. Thanks.

Brad...

 

There were so many service bulletins on the Ford electronic ignition system modules from that era that they were contained in their own volume.

I've not only heard of, but SAW a friend with a two-year old '78 Ford XLT (the big one at that time) go through four modules within a week. Each one was good for about 150 miles, then it would "flake out" intermittently. The subsequent replacement woudl act fine for another 100-150 miles, then do the same thing. After four modules and a visit to a more reputable dealer service department (one that could actually READ) he had some wiring re-routed and another module installed, and there were no more problems.

In short, don't overlook the fender-mounted module itself. As for the coil, you can disconnect the wiring and meter the coils. The primary winding should have between 0.1-1.0 ohms. The secondary side should be between 6,000-10,000 ohms. You should also meter the coil wire and plug wires for resistance. You shoudl expect about 200-350 ohms per foot of wire. Anything more indicates a wire that is breaking down.

 

I'll agree with Vader, 90% of the time its the fender mounted module. We use to get so many of them that we keep a spare module in the shop. Just plug it in and see if its cured. Usually faster than diagnosing something and ALMOST always works. Sometimes though you get one like Vader was talking about and get hung up, but i'd be willing to bet its your module.

They make like 3 different modules. You can tell them apart by the color of the plastic block where the wires go into the module. Usually theyre blue. You may need to know this to get the right one.

 

Sounds like the ignition module is bad.

Theres also a wire on most fords under the dash, its a super long fusible link wire that runs to the coil. If that wire is corroded and/or damaged in some way, the ignition will be weak and have problems. Its a much less likely suspect than the POS Duraspark module though...

 

Right on. Thanks guys. He said he had the modual checked and it was fine. Maybe it just works when it wants to. We'll get a new modual and see what happens. Thanks.

Brad...