Is there such a beast as a "spotters" guide for ignition modules?
Heres why I ask, I have a project truck, 1991 F150 Supercab 4x4. I've swapped the 302 to a (I think, I can't remember) 73 to 79 351W or a 82 W, got it running except it keeps burning out modules, I had this project sitting for the past 8.5 years, I'm back on it again, however I cannot recall what year module I started the project with, I know I need to go back to the ignition switch and hook up a resister wire to lower the voltage to the module when the ignition switch is in the run position, but I'd like to get a module from the wrecking yard as a back up so I can drive truck and see if its working correctly now?
Any ideas??

 

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Duraspark modules require a FULL 12 volts. They will not function properly with a resistor in the input path. The resistor you're thinking of is the ballast resistor for the coil primary winding, which serves a different purpose.

The first thing to check on a vehicle that consistently fries ignition modules is the voltage regulator. Measure the voltage across the battery posts with the engine running.

 

[QUOTE=superhooperduty;13609416]Is there such a beast as a "spotters" guide for ignition modules?
Here's why I ask, I have a project truck, 1991 F150 Supercab 4x4. I've swapped the 302 to a (I think, I can't remember) 73 to 79 351W or a 82 W, got it running except it keeps burning out modules, I had this project sitting for the past 8.5 years, the truck will start and run fine but after maybe 20 minutes the module is very hot, it has fried at least 2 modules, does the module need to be mounted to ground it or does it matter?
I think I've got the orginal 91 module in it, at least it seems to have the same number of wires with the same colours of wires as the diagram in the book, the red supply wire to the module is hooked but the white isn't, its been cut off, anybody know where the white wire runs from?
thanks

 

Will do thanks, as per my second post, any one know?

 

I'm confused. What ignition module do you have? Is this a TFI module? If it's using ignition off a '91, why are you posting in the 73-79 forum? I don't really understand what you're working with. Can you show a picture?

 

Sorry A picture will not show you the issue, here goes, I swapped he 302 out of my 91 f150, inserted a 351w with a carburetor, I've over come the fuel supply issues, transmission issues, etc, the problem I'm having is that its eaten 2 "Duraspark II modules( I'm not sure of the year of the module, but its got the blue plastic on it) engine runs fine, but after 20 to 30 minutes of continuous running/ driving the epoxy on the back on the module melts, frying the unit. I'm sure that this is NOT a TFI unit, its from something older 73-82 ish. From any pictures I've seen it doesn't look like the TFI system. The distributor is not a TFI, Thats why I'm posting in this forum.
I have a square MSD ignition coil hooked up to it, According to the wiring diagram I have the module is fed power from the ignition switch thru two wires, red when running and white(and it looks like you could get some thru the red in series with the ballast resistor) the green, orange, purple and black from the module go to the distributor. Some one has( maybe I did it or maybe the person who owned the truck before) clipped the white wire thats in the same as the red power supply wire, I cannot see where this wire was clipped from, but in any case it starts fine and runs fine until the module frys. I know that the module needs a full 12v but can it be supplied with too much voltage, last night I had the truck running and I checked and and 13.34 v at the red wire to ground. I was considering finding a point style 351w distributor there by cutting out the module completely.
Any thoughts?

 

I'm not sure on the module but a recommendation on the coil. Get a stock replacement coil and loose the MSD. If you are not sure try a '78 F250/400 replacement coil.

MSD makes great parts but its not matched up electrically to the Duraspark box and system. That could be your problem. Besides with and OE distributor,OE plug gaps and a mild build, the hot coil isn't really helping anything.

 

I'll give it a shot, if I can find it , will the orginal coil that came on the truck work??
thanks

 

If the voltage at the RED wire is fine (13-14 volts is normal) but the module is cooking, then the module is sinking too much primary current, or both modules are bad. There's a good chance your "performance" coil is pulling too much primary current through the module. Go back to an OE coil. There's no reason to use an MSD coil with a Duraspark box.

I'm not sure where you're getting your ignition modules from, but stay away from the sub-$30 rip-offs from the parts store. Run nothing but Motorcraft modules and stay away from "performance" coils.

Also make sure the ballast resistor is actually in use. Turn the key to RUN, but keep the engine off. The voltage at the positive terminal of the coil should be between 6 and 7 volts (the module has to be hooked up and functional). If you see upwards of 12, someone has bypassed the ballast resistor and this will add to the stress on the module, contributing to your problem.

 

The original coil, if it is mid/late 70's vintage like the module should work fine. If you can't find it, your local AP store probably has one. Rock Auto also... along with the Motorcraft ignition modules.

 

I have time today, to test it, and thanks for the great info.
I'll keep you up to date.
would be great to get this running at least till I get my new truck

 

1U2Z-12A199-AA (replaced D6AZ-12A199-A - C8VZ-12A199-A - C9VZ-12A199-A) .. Ignition Module-Blue (Motorcraft DY-893).

Myriad: 1976/87 FoMoCo Passenger Cars & 1976/97 Trucks/Bronco's/Econolines.