What are you trying to power? The Red wire on the control module should be battery voltage.

 

 

Try the I wire on the starter solenoid. It's function is to supply 12v while the starter is cranking.

 

The ignition switch has this function (hot for crank and run) for the coil positive wire. If your EFI system uses this just as a trigger to turn on it should have enough juice.

Main power for the EFI is usually a "strong" always on source like the main fender relay terminal or battery +. .

 

On at least some Ford ignition switches, the Green w/red voltage regulator circuit is also powered in both START and RUN. If I had my choice I'd tap into a regulator wire before tapping into an ignition wire. But then, if your ignition is no longer stock or controlled by the old Red w/green wire anyway, then that's the perfect source.
Same for the voltage regulator wire too actually. With so many switching over to internally regulated alternators, the old Green w/red wire will often be modified to reach the new location anyway. Tapping into it as well should not create any trouble.

As said too though, the starter relay's Brown wire has power in START (only) and just about any other wire from the ignition switch is hot in RUN, so if you were feeling bold and energetic, you could tap into two separate circuits to achieve the same result in a pinch.
But that seems like way too much work to me.
Although, thinking about it more, espy's suggestion is still a good one. The Brown "I" wire has power in START obviously, but since it is also connected directly to the Red w/green ignition wire at it's other end it will also have 12v in RUN.
So it's a good source in a pinch.

Paul

 

In my experience cranking voltage at battery will be approx 11 volts but can be effective down to approx 9 volts (so any direct battery feed will provide battery voltage but during cranking this might go as low as 9v).
Volts will get dropped by a poor starter circuit so if your voltage is dropping too low then suspect the starter circuit.

Apologies, seem to have misunderstood, I thought the problem was a voltage issue not a source wire issue.

 

You can use your old coil wire and just bypass the resistor. I'm thinking that the ignition coil is the only circuit not powered when the key is in Accessory mode, so that's what you want for ignition power, and probably for an EFI controller.

I think the best place to get the 12V+ while cranking the starter is on the "I" terminal on the Fender Mounted Starter Relay. This is where the Duraspark ignition sources it.

I believe there is a diode inside the starter relay, which keeps current from back-feeding to the "S" terminal, where it could cause the starter to stick on. I once converted a '68 Cougar to Duraspark ignition, and assumed that I could just get my cranking 12V+ from the "S" terminal, but the starter would stick on sometimes until I wired it correctly - which might've required a different starter relay with the "I" terminal - they didn't all have that terminal.

 

The "I" terminal on the solinoid is only fed 12v while crankiing, during run it has voltage backfed from the coil, so low voltage from the resistor. Not a good source for the EFI.

 

Does he have any blank ACC or RUN spaces left on the fuse block? If so, he could tap from there to the coil, with the previously mentioned I wire spliced in. There are many other ways to accomplish what he wants. One way is to add on a continuous duty solenoid. This will give him flexibility when adding on other goodies in the future. It can even help him to clean up existing wiring in the truck.

 

Not sure about these fuse panels specifically, but most of the older Ford setups I've worked on had only ACC positions, along with the battery feed busses. They would then (theoretically) lose power in START generally speaking.
So he'd still need to have a power-in-start source.

But that theory is easy enough to test. Put a test light on a switched fuse, then turn the key to START to see if it keeps it's power. If so, done!

Paul

 

When I installed my HEI, I tapped into the 'RUN' wire at the ignition switch. Ran that wire into the HEI coil. Ran a separate wire from the 'I' terminal on the starter solenoid. This wire was spliced into the 'RUN' wire before the coil connection. End result is that there is always a 12v supply to the coil with the key in 'RUN'. Even though there will always be 12v at the 'I' terminal in the 'RUN' position, it will not back feed into the solenoid unless the solenoid becomes defective. I have had that happen once. It took awhile to figure it out.

 

The Holley Sniper EFI installation video covers this issue at the 7:50 mark. The clean 12V source is fine dropping voltage down a normal amount while cranking. I am in the process of installing a Sniper on my truck and have the pink wire hooked up to my 12V electric choke terminal in the oval plug located on the upper passenger side of firewall.

David

 

I believe there's another thread running right now on this very topic, too, some good ideas there as well. Big help for the voltage drop is to use a relay off the battery, and switch it with your power source (sounds like there's a circuit on the ignition module that'll work) - by using heavy wire right off the battery and bypassing 2 miles of too-light wire, a suspect factory fuse panel, and 40 years worth of corroded connections.......

 

How did the pink wire hooked to the 12v electric choke terminal work as a switched 12v power source? I have a 1983 F150 and in the process of installing a Sniper now. Disconnecting the electric choke wire from my old carburetor and using this wire as the pink wire switched power source would certainly make it easy. Please tell me how it worked for you. Thanks.