FasterCat

After a year of hard work, the Cat is (mostly) back together and ready to pull out of the garage !

.... but, I have a little problem:

I spent yesterday trying to start her ... spinning the starter, checking for spark, spinning the starter, rechecking everything, spinning the starter ....

.... it appeared that it wasn't getting spark at the plugs when I was turning her over with the starter ?

Every time I tried to start her, I "fully engaged" the ignition switch to the start position, and she never started (yesterday)

So I gave it a rest.

Then this morning, I tried to start her again, and as I "gently released" the ignition switch from start to "on", she fired right up !
And she runs just fine.

She will only start when I "gently release" the ignition switch from start to on. If I just hold the ignition switch in start, she won't kick over at all.

Any ideas ?

Among other things, I have a Duraspark conversion ... and yes, all the wiring has been checked, rechecked, and rechecked again. It is actually a fairly simple conversion. It has a solid keyed 12V (direct) from the ignition -I did not remove the resistor wire from the key to the coil - I know, some people prefer to run a keyed 12V direct to the coil with the duraspark conversion, and some people don't. .... maybe I should check the Keyed 12V from the ignition when the starter is turning ? ... and maybe I should check the + voltage at the coil when the starter is turning ? .... If they were low ... why would they be ?

The "internals" of the car a pretty much all new + restomod = electrics, brakes, drivetrain.

socalwrench

Sounds like a bad ignition cylinder (the key lock with the tumbler).

67t5ponycoupe

You have a circuit that comes off the starter solenoid to provide a full 12vdc to the coil when the starter is cranking. It sounds to me like that circuit is not working and the engine will only catch when you go to the on position because that is the point at which the voltage becomes available throught the resistor wire. Check the circuit on the I terminal of the soleniod.

FasterCat

The stock wiring to the coil + is still intact .... meaning that it has the "start bypass" circuit which supplies 12V directly to the coil during starting. (it has 12V in "start")

- "As shown in the drawing", I connected to the post in the center of my ignition switch
(which only supplies 12V in the run position)

Does the ignition power to the duraspark box also needs to be hooked to a "start bypass" ?

If so, where is the "start bypass" source in the back of a '67 ignition switch ?
.. is it accessible ?
... or do I need to splice into the beginning of the resistor wire
(at the ignition switch)

This is the wiring diagram I used (and it only shows the duraspark connected to the run circuit):

67t5ponycoupe

Cougar and Mustang should be same same and on a Mustang the voltage source to the coil on start comes directly off the starter soleniod.

FasterCat

.... ahhhhhh .... I see ...

so from what you have pointed out, the "brown wire" on the solenoid routes all the way back to connect with the "output" of the resistor wire which connects to the + side of the coil ?

So ... I could get the "on a start" voltage to my "on at run" wire to the Duraspark by tying it directly to the "output" of the resistor wire (effectively negating the effect of the resistor wire).

This would also be supplying "run at start" voltage to all the other circuits which are connected to the keyed "on at run" circuits .... any problem with this ???

67t5ponycoupe

That all sounds correct. The brown wire on the soleniod provides the full 12vdc at start and is electrically connected to the output of the resistor wire essentially bypassing the wire. The physical connection is actually made at the plug that penitrates the firewall. That full 12vdc does not go back throught the fire wall to connect to the resistor wire though. I tell you this so if you are tracing it you won't go under the dash to look for it. It is all in the engine compartment.