prestolite to motorcraft ?s

I have a 74 with a 304 from a 77
I am getting rid of the prestolite ignition for the motorcraft.
I am not doing the tfi upgrade.
I ordered all ignition parts from a 78
my question is do I need the resistor with these?
and can I still follow the wiring diagram for the TFI upgrade?

 

Ok, the TFI upgrade does not require any new wiring. The '78-on Jeep stuff is the Motorcraft Duraspark ignition. TFI is different, and is an upgrade to Duraspark. It includes the Ford cap, adapter, rotor, wires and coil. The Duraspark module does require a ballast resistor IIRC...

I have the TFI stuff in my CJ-6 on a '78 distributor but I'm running a GM HEI module. I'm also using a 3 ohm Pertronix coil, which will limit the current to the module.

Which diagram are you using? Give us a link.

Here's one diagram:

 

I am using a diagram posted by LBGORS I can't seem to link it.
on inspection it is the same as the above post.
that is how it is now wired but I am not doing the TFI upgrade.
after I installed everything it started right up but the resistor got hot maby that's normal. now it won't start at all.
there is 12 volts at the coil in start and in run. but no spark. I just tried two coils one is new and the other was working fine.
now im stumped

 

I had 12v at the coil positive and at the neg. that seems wrong.

 

Did you add a ballast resistor? The Prestolite system does not have one, as I recall.

You will have 12V at both terminals of the coil if the module is not conducting. If the module conducts, then one side of the coil will be 8-12V and the other will be close to ground potential.

About the only way you can see the voltage changing is with an oscilloscope.

 

Just copy and paste the link. You don't need to show the image.

 

yes I did use the resistor and it got hot don't know if that's normal.
the diagrams are the same.
what do you mean by conducting? when should it conduct, when starting/running im assuming. if that's correct, voltage at the neg post when not running with the key in run is normal ??

 

You can think of the module as a switch, just like points. If the switch is open, it does not conduct. Closed, it conducts. The spark only happens when the switch opens, and the magnetic field in the coil collapses.

If the switch is open, both sides of the coil will be at full potential, ie 12V. I'd expect this to be normal with the key on and the engine not running.

 

good info but its not telling me why there is no spark.
in the diagram above it "highly recomends" adding an extra ground to the black wire from the module.
I don't have that could that be my problem?
without the added ground how is the system grounded?

 

The black wire is grounded at the distributor.

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The green wire energizes and disconnects the coil to make the spark.
The red wire supplies power.
The blue/white wire retards the spark when starting for easier starting.
The orange and purple wires connect the module to the magnetic sensor in the distributor.

When starting, power goes to the module (red wire) using the connection to "I" on the solenoid. After starting, "I" is disconnected and power is supplied from the ignition switch, through the resistor.

 

So you say your module does not have that black wire? If not you could run an extra wire from the metal module case and connect it the the metal distributor housing.

 

so I had the red wire from ignition on the wrong side of the resistor, glad I found it but don't think it was the problem. added the extra ground wire and all is well. thanks for the help. this is an awesome forum