I am working on a 69 firebird . I put a complete msd ignition system in it. ( Pro billet dist. ,Coil, 7AL box) I need to find a power source for the 7al box which has power with the key in the run position and also the start position. I am tied into the original coil supply wire ( black w/ purple stripe) but it only has power to it with the ignition in the run position. When you go to crank position that wire drops to zero volts. It has a one wire alt setup and a mini starter which has no R post on it to send power to coil while cranking. Any ideas where I can easily tap into a keyed power source that has 12 while key is in the run position and also the crank/start position?
If I remember correctly, and if you are running the stock fuse block, you should be able to connect to the IGN blade terminal there for a 12 volt source.
Did you wire your mini starter with the purple wire from the start switch directly to the starter or did you put a starter solenoid in and eliminate the starter wire from the switch? If you added the solenoid you could hook up the ignition to the remote solenoid.
The purple wire connects the ignition switch to the starter S post when in start mode only. If you added a wire [ original yellow?] to the S post of the mini starter and ran it to the ignition box you would have power in the start and run position. You would have to put a diode in the yellw wire to enable juice to flow from the S post of the starter to the ignition when in start mode but not allow juice to flow from the ignition to the starter while in the run mode. I would go with adding a solenoid near the battery, powered by the starter wire, which would give you power to the starter and ignition when the switch is in start. You run the battery cable to the solinoid and the cable from the starter to the solenoid. One only has to put a jumper from the S post to the BATT post on the starter.
Does the MSD ignition require a full 12 volts to operate? The original coil wire is a resistor wire and will only give you 6-9 volts at the box. You could add a relay at the box and have it connected to the battery. When the relay is powered on with the resistance wire it would supply battery power to the ignition.
The MSD box has a heavy red and black that should be wired directly to the battery. Use the +12 switched power that is mentioned in above post. Should verify that it has a full 12v with a volt meter.
I'll have to look but I think my 6al box is wired right to the battery with an in-line fuse. I suppose it's hot any time my battery is hooked up, car running or not.
Yes I am just running the purple wire from the key ignition to the S stud on the starter. It cranks over great . No problems on that end. The MSD does require a full 12 volts. I am supplying the heavy red wire on the MSD box directly from a battery feed. And the keyed MSD power source I am feeding with the original coil+ supply (black wire with a pinkish stripe ) It has 12 volts going to it when the key is in the run position. But when you turn the key to the crank/start position the voltage in that wire drops to zero.
I don't have knowledge about the ignition boxes but from what I read above it's powered from the battery and is switched off and on by the ignition switch. I'm surprised you have 12 volts at the original coil + wire but at least you have what you need in the run mode. For the start mode, I'm sure there is a wire that is keyed on in both the run and start position, although I can't think of one right now, maybe the accessory post? I'd say your best bet would be to use the starter to power your ignition box on during cranking. Instead of connecting it to the S post, as I suggested in my last post, run a wire from the motor post on the starter to your ignition box. The s post on your starter is where you have the purple start wire attached but that may drop down below 12 volts due to the power being used to hold the solenoid closed while starting. Your High Torque starter should have three posts on the solenoid, the BATT post, the S post [ or blade] and the M motor post. The M post is just hot when the solenoid is closed during start but the solenoid connects it to the BATT post internally. Just be sure to put a diode in the wire. A diode allows juice to flow one way and not the other, like a one way check valve. The diode will allow the power to go from the starter to the ignition box during starting but stop power going from the ignition box to the starter in run mode. You can get a diode from radio shack or any electronics store, buy one with wire soldered to both ends so you can splice it into your starter-ignition wire. A 10 amp 250 volt diode will work well. The end with the stripe [cathode] goes toward the starter.
My 69 goats have a wire especially for providing power to the coil when cranking. I'm sure the 69 bird is the same. Get a wiring diagram and you should be able to find it. The ignition switch is wired so that when you are cranking the starter, the regular power to the coil (that runs through the resistance wire) is turned off and the other wire is energized. I had to figure that out on mine when I added pertronix and had to bypass the resistance wire.
I used the ign terminal in the factory fuse panel on my '68 for the switched source on a MSD 6al programmable. Heavy red wire connected directly to the battery.
