I cannot get spark from my 1979 F-350.

Here is my setup per the moment...

12v from RUN to Ballast Resistor to positive post on coil.
Ballast Resistor to positive (Purple wire) on distributor.
From negative post on coil to Orange wire on distributor.
Distributor is grounded.




This is exactly the setup I hooked up.

I can provide any pictures or information needed otherwise. I am getting over 12V (13.3 to be exact) at the coil, from both the positive and the negative posts. However I am not getting any spark at the distributor.

ANY HELP WOULD BE MUCH APPRECIATED!

 

It seems you're missing the ignition module? Or are you running an old points-style ignition?

 

This is typical wiring for a Duraspark electronic ignition system:

 

The distributor in the truck now is pointless. There was an MSD box in the truck originally. However I'm fairly certain the box has gone bad. So I decided to attempt to by-pass the MSD box. This made more sense anyway because I was using an older harness from a 1973 F-350. I did question whether or not this pointless distributor would work with just a ballast resistor between the ignition.

Otherwise im not sure if there was an ignition module as well as the msd box. i thought that took its place?

 

The MSD box was your ignition module. You can't bypass it.

The pickup coil in the bottom of the distributor acts as a Hall effect sensor and sends a very low-voltage timing signal to the ignition module. Transistors in the ignition module then route power to the coil to charge and discharge it at the right time. The way you've got it wired up, you'll be lucky if you haven't already burned up the coil and/or distributor pickup. Neither is intended to have 12V supplied to it constantly; the pickup isn't ever intended to have any power supplied to it at all.

You need to add an ignition module in order for the system to function. A Motorcraft Duraspark II module would be my choice, but you definitely need something.

 

The ballast resistor is just there to reduce the voltage to the ignition module/coil for normal operation to ~9V while a full 12V can be provided during startup. It is not an ignition module, nor does it serve anything like the same purpose as one.

 

Hmm, well I hope I didn't burn it out. In any case, I'll be using your wiring picture and going back at it in the morning.

Thanks for the help, obviously I need it.

 

No problem. Good luck!

 

So i hooked up the wiring as best I could and put the msd box back in the truck. however still no life.

So what suggestions do you have? should I buy an ignition module and or distributor? Or is there a better way to go about this? I was considering an HEI distributor. Would this be easier to hook up, simpler?

 

I bought a Standard Motor Products LX203T Ignition Module Control Unit. Will this work with this diagram?

 

Yes, that ignition module should work with a Duraspark distributor, wired as shown.

On the ignition switch, see the S & R? Those stand for Start & Run. So yes, the wire you call out is hot in Run. And yes, the hookup from the start position to the positive side of the coil is necessary. Without it, you wouldn't get any spark when cranking.

 

As for an HEI swap, the wiring is simpler, yes. Others on here have done it - a search would bring up good documentation there.

If the new ignition module doesn't work when wired as above, the problem would most likely be either the coil or the pickup in the distributor.

 

HEI!! One 12v wire and the plugs

 

so just 12v, ground and the plugs? thats it?

 

Not even a ground, it grounds itself when you put it in the block.. just a 12v signal and the wires