I did the TFI coil and eliminated the resistor wire totally(had the harness out) and ran a full 12v to the coil and DS II module box. The truck stalled and wouldnt re-fire. I started smelling something 'electrical',so I got to pokin around and found the module had a hole melted right through the center so I had another layin around and the same thing happened. I have double checked and checked again the wiring, I soldier,tape and heat shrink all my joints/splices. Could too much resistance at the coil cause this? Any help would be greatly appreciated. For now I put in a Standard Ignition module and coil and am using a ballast resistor to cut the voltage down. But I want to go back the the TFI coil. Thanks
BTW I should mention it's a '77 F250 w/ 351M 4spd....stock

 

The resistance wire, cutting back the voltage, protects the module. The Duraspark II doesn't need or want a full 12V, and failure will occur as you have discovered.

The only way to use a full 12V would be to use another type of ignition module (i.e. MSD, Mallory, etc.).

 

This is the diagram I went from. I have done it before without any problems. I dont understand whats wrong now.

 

You simply cannot do this with a Duraspark module. The Duraspark module is designed to operate with a specific range of current through the primary winding of the ignition coil. With the resistance wire gone and the lower primary winding resistance seen with a TFI-type coil, the current you're putting through the power transistor in the module is much more than it's rated to handle.

If you have gotten away with doing this in the past, you were still stressing the module beyond its design limits and simply got lucky that the module was robust enough to dissipate the extra heat. Whoever drew your diagram is misinformed and does not understand the design limits of the system.

 

Ok, Thank you. So it looks like I am going to removing the wiring harness again to replace the resistor wire!
Do you happen to know the resistance value of the wire? Can I continue to use the ballast resistor?

 

The ballast resistor is the resistor wire - not sure if I understand the question. I want to say the resistor wire is typically 1.3 to 1.4 ohm - but I'd appreciate if someone else can verify.

Note that simply adding back in the resistor wire doesn't gaurantee the problem will be solved. You need to use the resistance wire and the Duraspark coil to create the total series resistance. A TFI coil typically has a lower primary winding resistance than a Duraspark or points coil.

 

The resistor wire is 60" long and measure 1.4 ohms. A ballast resistor of 1.1-1.4 will work. Here is another diagram actually using a TFI coil.

 

That appears to be the stock wiring diagram. I have added the resistor and the stock DS II coil back into the system and it runs fine. I just wanted to go with s hotter ignition...and not MSD....something that can be gotten at the local auto parts store if needed. Thanks

 

Have you opened up your plug gap? With the DSII you can open the gap up to .044, sometimes more, for a healthier spark.

 

Yes, the gap is @ .044

 

These guys are right about the DSII. I tried to get away with an MSD street fire E-coil and no ballast resistor on mine this weekend, and my Echlin DSII module got deep fried. Some folks pointed this out to me yesterday in a post I made regarding a failed attempt to get the HEI/DSII hybrid mod to work. They are trying to help me figure out what is going on there, because I also wanted to eliminate the ballast resistor with the HEI setup. Anyway, Ohm's law tells us the following:

I = V/R where I = current, V=voltage, and R=resistance

Therefore, voltage and current are directly proportional while resistance is inversely proportional to current and voltage. If only the ballast resistor had been removed and the normal DSII coil left in series, voltage would have increased, and also current. Right there, we are already jamming more current through the DSII module than it can handle. E-coil replacement also drops primary coil resistance by a factor of ~2 with voltage remaining constant. Therefore, current doubles according to Ohm's law. The bottom line is that way too much current is going through the DSII module in this situation, and it overheats.

Now, I wish I could get my HEI conversion to work so I could have a simpler system, but it is not working on my truck for some strange reason.

 

this is the diagram I have for that conversion. I may just go that way also.

 

I don't get it.

How did you come to the conclusion that the HEI conversion is "simpler?"

And why would anyone go through the trouble of hacking up your factory wiring to trade one ignition module for another?

And why would anyone even want a GM ignition module in a FORD? There is absolutely nothing to be gained by doing this.

 

Good luck with that mod Lance. It didn't work for me with a BWD module from advance auto and a cardone DSII reman distributor. I used that exact same wiring schematic that you are showing. It wouldn't fire. I know many folks have no trouble at all with that schematic, so there could be some kind of issue with whatever stator the cardone DSII dizzies use and the BWD HEI modules. Keep that in mind when you shop.

Lariat, the HEI is simpler because it doesn't have the ballast and all the different junction points that the DSII has. As far as which is the better ignition overall, they are pretty much identical in firepower. The HEI is cheaper to replace if the module dies too. There are pluses and minuses for each setup. In my case, it didn't work, so the minus is that I have a useless module laying around.

 

So is it "simpler" to remove the resister wire from the stock ignition, and then wire in the FOUR (4) extra wires for the GM ignition module? Only now instead of an engineered stock Ford ignition system, you now have a GM "hybrid" ignition under your Ford hood that doesn't even gain you anything over what it originally came with?

What am I missing?

And for the record, the GM ignition module is absolutely not cheaper than a replacement Duraspark ignition module, sixofspades.