Truck starts and runs good for awhile. Then it is like someone turned it off. sometimes it starts right up other times it takes awhile. Changed the coil, all the electrical parts in the distributor, the box on the fender wall. key tumbler and the plug to the ignition switch.

 

when it doesn't start right back up, have you checked for spark and/or fuel to know what's missing?

 

fuel is fine. It is spark, yes I have checked.

 

Driving down the road, pretty soon the truck will backfire like turning the key off and on. Then it will die.

 

Anyway to check the voltage on at the coil before you start it with ignition on versus when the engine dies?

Might be the resistor wire under the dash...

If your starter relay or solenoid has the I terminal plugged in, it should start and run until the relay is deactivated.

 

Mine did the same thing today, just shut off no warning then no spark. Only 3v on the "I" terminal and 3v on the coil. It used to have 12v there before.... I'm running a pertronics ignitor 3 insted of points, and a pertronics flame thrower coil.

My book says a points coil is supposed to be 8v? Can i just get rid of this main resistor wire and run 12 to the "I" terminal and to my coil?

What is theory behind the "1.05 to 1.15 ohms red/green main resistor wire"?

Where under the dash is this "main resistor wire?"

I'm pretty sure i know how i broke mine. I used that wire for my relay on my 95 t bird fan. I'm sure it toasted the resistor. I didn't know there was a resistor in the wire or i would have ran a new acc wire. I just thought it was a normal accessory wire.

 

Lol also what should the spark plug gap be of your running the pertronics kit cause a points ignition had a different gap then a solid state ignition right?

 

From pertronix
"While it's the perfect coil to go with the PerTronix Ignitor breakerless ignition, our 40,000 volt Flame-Thrower canister coil can benefit virtually any distributor type inductive system. Its higher voltage allows larger spark plug gaps for added power, smoother response and better fuel economy. These coils are internally resisted so they are compatible with many ignition systems."

So if it is internally resisted then i can bypass that main resistor under the dash right?

Sounds like it to me

 

Going to have to do some harness surgury to get to the wire. When I replaced mine, it went from about 6" from the fuse panel to about middle of dash. Expect to pull the dash apart and pull the stereo/heater panel to gain access.

The Resistor is used to limit current going to the coil to prevent it from overheating and burning out and to save on excessive wear on the distributor and rotor and spark plugs. The "I" wire from the starter relay is to supply full voltage during the greatest current draw is used by the starter motor and at the lowest voltage, which helps with cold weather starts. Basically, this provides a hotter spark to help start the engine.

Personally, I don't like the idea of a resistor wire bundled with the main harness under the dash and like the idea of a ceramic ballast resistor under the hood, but whatever. Check the wiring diagrams for sure, and if your replacing this wire, maybe consider placing a fuse inline and place the wire outside the rest of the harness with some heat resistance wrap.

In my case, I replaced the resistor wire with a 14 Gauge wire and used a fuse holder and a 10A fuse. However, I did ran a wasted spark coil that didn't need the resistor or even the distributor.

 

I got the dash apart went to radio shack. (Why would anybody put an alarm in a 75 Ford with one sensor under the hood and none in the doors? just to mess up the wiring?) Did you put the fuse before or after the resistor?

Dumb question, could the starter relay be doing this?
Thanks for the help!

 

Isn't/wasn't the resistor wire already fused?

But anyway yes, with a Flamethrower coil and Pertronix ignitor bypass the resistor wire with heavy gauge wire and run a full 12 volts constant. You can open the plugs up to .045 too. Just make sure the plug wires, cap and rotor and everything are in good shape. Check for any arcing with the increased secondary voltage, it helps to stuff all the boots with dialectric grease.

 

If your keeping the resistor wire, I'd place a fuse between it and power source. Don't know which end is the ignition power source though.

If the wire burns out and draws too much current, it should in theory blow the fuse. How much current it draws while burning out is another question I don't know the answer to

It's possible the engineers designed it this way so the resistor wire acts as a fuse...

 

Thanks tedster9 for the info, will do and get back to you. ZarK-eh good explanation on how the i terminal works that makes a ton of sense!!

You guys rock, I have some stuff to try now before the game starts.

 

Cleaned the base of the distributor and the truck fired right up ran good. I think my pertronix kit did that low voltage shut down.

I'm still not getting enough fuel on idle, my AFR is 20~:1 at idle the idle mixture screws on the Edlebrock are almost all the way out. Idle is at 800, timing is off cause if I move it on the solid lines on the crank pulley it runs like crap.

 

No need for a fuse in the resistor wire, it's only hot in the run position. Ford did not put one in, why would you? The resistor wire runs from the ignition switch out to the coil and should be removed out of the system and replaced from the ignition switch to the coil with a new 14-16 gauge wire to supply a full 12 volts to the pertronix. Pertronix I will work with the original Ford resistor wire most of the time. Pertronix II and III require a full 12 volts to work. Read the pertronix web site and instructions that came with the unit. It clearly states this. Do not use any type of resistor wire or ceramic resistor with the flame thrower II or III set up.


I have 3 1968 Ford cars, all have pertronix, all are wired this way, all run perfectly.