Okay, so I read nearly every post on FTE that Google would give up, and think I have the starter solenoid pretty well understood. Now I have to figure out how to apply it to my situation

I'm taking a half-day off tomorrow to get her back on the road after an engine rebuild. The ignition system is Pertronix HEI, so the plan is to get 12V from the (4 point) starter solenoid's "I" electrode to coil "+", so that the coil has voltage when the key is in the start position.

When the engine is running , the alternator will supply 12-14V down the wire which no longer contains a resistor (at Pertronix tech support's suggestion). That way, the coil will be energized when the key is in "run" and "start" positions. Assuming that the wiring and relay are working correctly, everything Should Work Fine.

But then there's the issue of the Electric Choke that's part of the E-brock 1406 carburetor that came with the engine. The choke's t-stat housing has a circuit built in. As I understand it, turning the key to start should provide power to that circuit, whereas being in "run" should have that circuit de-energized (the heat from the block should take over and expand the t-stat at that point).

But if I wire the electric choke to starter solenoid "I" or to coil "+", the power through the choke's circuit will be the same in the same state as the coil (energized when the key is anything but off). Where do I hook in the choke "+" so that there's no power when the engine is running?

Been noodling on this long enough, but every wire I know of allows voltage to flow in both directions...

 

The aftermarket choke needs power the entire time the engine is running. There's no special circuit, just a passive heating element. The only circuit that uses power in hot-in-START only is the starter solenoid (not counting any signals that may go to the ignition module).

You need to pull power off of a fused hot-in-RUN circuit. I would avoid using the same source as the coil, because coils can draw a significant amount of current.

For mine (Edelbrock 1403), I pulled power off what used to source the idle stop solenoid, which I could borrow off of a connector from the firewall. On my truck ('79), this is a hot-in-RUN signal that is protected with a 7.5 amp fuse in the fuse panel. This has worked out perfectly.

For what it's worth, the original stock choke pulled power from the stator terminal of the alternator. It's not a DC signal; it's a three-phase AC signal - but it worked out perfect because it's only hot when the engine is actually rotating (start, run, doesn't matter). Most aftermarket carburetor's just say to use 12 volts DC - so stick with that.

 

Anyone know of a likely source of hot-in-RUN +12V? Got my multimeter and circuit checker, but would like to wire it up before starting the engine...

 

As FMC400 mentioned, the alternator stator output is hot only when the engine is running. Beyond that you'll probably only find things that are hot when the key is ON. Newer cars have circuits that only operate when the engine is running, but then newer cars have computers and sensors that can tell them the engine is running.

Really it won't be a problem to connect your choke to a key-on hot, just don't make a habit of turning the key to the on position and leaving it there for an extended period of time before starting. Doing so would cause the choke to heat up and start to pull off before necessary.

Also as was mentioned, the alternator stator output is not 12VDC but is actually an AC power source. Technically you can use this for your electric choke but your results may vary. It may pull off too quickly, or too slowly, etc.

 

I did the stator terminal or "S" terminal. Couldn't find much else that was available without splicing. I originally had a fuse link but scrapped it as it kept blowing large capacity fuses.