TFI coil wiring question

[JohnNC]

Hooked up my new TFI coil this evening after modifying the bracket.

I am following the instructions provided on the various websites, but have a question regarding wiring the new cable.

My yellow wire was fried (no insulation remaining). I traced the wire down the harness until it reached a splice joining a green/white wire going to the ignition switch on the fender wall and a red wire. Rather than cut and resplice, can I run a new higher gauge wire directly from the ignition switch to the coil. I will leaving the red to green/white connection intact, but basically remove the entire yellow wire.

Am I missing something?

[woodstock]

If I understand you correctly, you're thinking of effectively bypassing the resistor wire. A lot of guys are running their TFIs like that, you get more volts to the coil all the time that way instead of just at start up. It works, I think the jury has decided that there shouldn't be any problems. But I would carry a spare TFI coil just in case...not a bad idea anyway. I'm going to remove my resistor wire sometime this summer I think, just for fun.

You swapped out your plugs right? .045 is the way to go on that, otherwise the TFI is worthless.

[viscacha]

I think the device on the (pass) fender wall you are referring to is not an ignition switch. It is the starter solenoid. The box on the driver’s side is the ignition module. The coil wire splices to the solenoid and also to a resistor wire in the harness. When the starter is cranking over the coil gets full battery voltage for rapid start. After the starter stops cranking the coil get less voltage through the resistor wire. You can bypass the resistor wire for full voltage at all times because the TFI coil can handle it. But the ignition module might not be able to handle full voltage from what people have said.

My TFI coil gets full battery voltage (12v) at start up and 8v running.

I think the biggest improvement with the TFI set up is the snap on terminals and the 8mm plug wires you can now install. There is also more gap between the terminals on the dizzy cap. Better performance is obtained by changing out the module for one of those expensive deals. Then change the springs in the dizzy for a real improvement. I don’t think most people do the last two things. I didn’t, but will if I ever get the engine rebuilt. :cool:

[Rande]

Steve has it right. The TFI coil can easily full battery voltage but the ingnition module can't handle that extra power. You will eventually burn it out. Simply replace the wire as it is now. If you would rather feed the TFI coil with full battery voltage, get an MSD6A ingition module and toss the motorcraft unit. This way you have a better module and full voltage out of the coil.

On my '83 J20, I just kept the low voltage wiring stock an kept the motorcraft module. Still saw a very nice improvement in the engine.

[JohnNC]

TFI upgrade is complete and adjusted timing a bit following getting everything back together. The thing runs fantastic and I am glad I went through with the TFI upgrade.

Gapped the plugs to 0.045. The back two on the passenger side were easier to get from below than above.

thanks for all the help

[millertime]

whenever I do the plugs I whooop out the longest extention I have to get the drivers side plugs. For the passenger I turn the wheels over to the right (maybe left) and get at those 2 back plugs from underneath. The 2 front passenger plugs are ez.