Wiring advice needed for MSD 6al 1973 F100

bubba22349

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You need to use the Red / Green stripe wire that's hooked to the Posative / Distribtor coil post or else tap into the Pink wire on the back of the ignistion switch if you probe that wire two to three inch from switch you have a full 12 volts any further then that it will be behind the resistor and regulated to 7 to 9 volts. In my OPIN you shouldn't be tapping into the alternators voltage regulator for anything besides the alternators use. The I post of the Solinod is used to supply a full 12 volts (with a points type ignistion system) to the coil during starting only ((key turned to start) so don't use that source. You will need power during the on or run position of the key. Good luck (y) :nod:
 

Jesse73

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sixtseventwo4d":1frv5vr1 said:
The flickering is your ignition pulses from the coil (backfeed) while running. This is normal

That was my suspicion since it reads 6.7 or so volts when running. I think I’m confusing using the “I” terminal and the positive coil post. I didn’t have time to work on it tonight but I think I am going back to the original idea of pulling power from the key terminal.

Thanks for the patience guys it seems like it takes me a long time to sort out this basic stuff
 

old28racer

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Do you have the old style glass fuse holder or a newer plug in fuse style. If you have the newer plug in style you can get an adapter that plugs into the system with a 12 volt keyed wire coming out of it. Then you plug in the fuse to the adapter. Reel clean & easy setup.

I still think your original Ford keyed pink resister wire to the coil that is 6-9 volts will trigger your relay also.
 

Jesse73

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old28racer":6jgh3jrh said:
Do you have the old style glass fuse holder or a newer plug in fuse style. If you have the newer plug in style you can get an adapter that plugs into the system with a 12 volt keyed wire coming out of it. Then you plug in the fuse to the adapter. Reel clean & easy setup.

I still think your original Ford keyed pink resister wire to the coil that is 6-9 volts will trigger your relay also.


It is the glass fuse style. I think the relay I picked up won’t trigger with less than 12 volts. Yesterday I just hooked the trigger wire to the battery so that I could play around with the AFR meter and it worked fine.

I have seen little tiny things that would clip to a fuse in a holder, do they still make those? Thinking maybe I saw one on my fathers Packard fuse block or something like that. Something like that might work for my use.

I’m glad I have started messing with wiring the AFR gauge first, getting that wiring set up properly will be critical for getting the MSD unit a good power supply
 

bubba22349

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:hmmm: what's the amp rating of the relay your trying to use? As I said before if you going to supply a full 12 volts to trigger the relay then you probally don't need to even use the relay it all depends on the amp draw of the MSD. I have used the suit case style wire connectors (see below links) on the Pink wire just behind the ignistion switch to do the the DuraSpark II swaps into the earlier cars and trucks without needing to cut or damage any of the stock wire harness. Good luck (y) :nod:

Wire Conectors

Suit Case Style
http://img354.imageshack.us/img354/8158 ... ideft1.jpg

T Type Can Work Also
https://images-na.ssl-images-amazon.com ... hseL4L.jpg
 

Jesse73

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I’m using a 30 amp relay.

I guess in reality the MSD gets full power from the power wire, and just triggers on/off from a smaller separate wire. I should look at see what the voltage requirements are for that.
 

sixtseventwo4d

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Your typical Bosch style relays are less than one amp draw for operation, it's actually about .7 amps and voltage needed is marginally 9volts. BUT!! you need to be sure that the circuit you tap into is powered up when your key is on AND also during cranking. The original circuit that went to power your coil would be ideal since this was it's job
 

bubba22349

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A digital MSD 6A or 6AL will supply its full ignition plug voltage with a minimum supply of only 9 Volts (or can conected.to as much as 18 volts) and it uses only 4.5 Amp's at 5,000 RPM. The power requirement will go up of down .9 amps with every 1,000 RPM of engine operation. :nod:
 

old28racer

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Those are the ones I used for my trigger wire, just need to find a keyed glass fuse in your original holder. NAPA also has them. I still like to use the fuse tap to trigger my Bosch relay & pull a 12 volt wire from starter solenoid to the relay 12 volt input.
 

old28racer

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As an added note I run my GPS Odometer, AEM AFR Gauge & Purtronix Ignitor 1 unit off the same Bosch relay. Sure you can run your MSD 6al & AFR gauge off the same relay. Makes a nice clean wiring setup.
 

Jesse73

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ARG!

Last night I gave up on the relay working and started wiring up the MSD with the intention of hooking the trigger wire to my fuse panel. Got everything wired up, hooked to the fuse panel with a tap, keyed hot works etc etc. MSD box passes the spark test as outlined in the manual. Tried starting and nothing. Pulled a spark plug and there’s no spark. Bleh.

This morning I went out and did a quick check, my keyed hot is not powered when cranking. Arg. Have to go back and hook the trigger wire to something else.
 

THE FRENCHTOWN FLYER

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… or keep what you did and just tie in a jumper wire from the 'crank ballast resister bypass' terminal on the starter solenoid.
 

bubba22349

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:hmmm: so how much of the stock wiring have you changed or modded now, any pictures? :nod:
 

Jesse73

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I technically haven’t made any changes to the stock wiring harness besides connecting the power trigger to the radio trigger wire. I replaced the stock distributor with a DS2 so that everything could be put back to stock points if need be. I’ll have to work on posting pictures
 

Jesse73

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sixtseventwo4d":2ejiozyo said:
Your typical Bosch style relays are less than one amp draw for operation, it's actually about .7 amps and voltage needed is marginally 9volts. BUT!! you need to be sure that the circuit you tap into is powered up when your key is on AND also during cranking. The original circuit that went to power your coil would be ideal since this was it's job


I should have paid more attention to this comment. I indeed needed a wire powered both with the key on and also during cranking over.

Project update. Just to see if the truck ran I hooked the MSD power trigger to the battery and the engine started. When it was running I hooked my meter to the old positive coil wire. It shows 12.00 volts. So I hooked the MSD unit to that wire using a bullet connector that fit the old boot style terminal. Truck starts and runs fine now. Dialed in my timing and the electronic ignition is all set.

Not sure why that coil wire shows full voltage? Isn’t it supposed to be resisted down? Possibly a previous modification done to it? Unless I’m totally miss understanding how the points system worked.

Getting back to the relay, I found out that I had a bad ground connection. Meter on my ground showed the voltage wavering. Found a better ground and now the relay works to supply keyed hot power to the AFR gauge.

Now back to tuning the carb etc...
 

pmuller9

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Jesse73":16qkoyc2 said:
Not sure why that coil wire shows full voltage? Isn’t it supposed to be resisted down? Possibly a previous modification done to it? Unless I’m totally miss understanding how the points system worked.
I covered it in post #13.
The ballast resistance is on just over 1 ohm.
If you are drawing a small amount of current through that resistance there is very little voltage drop.
The MSD on wire only draws milliamps.
 

bubba22349

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Jesse73":bdjp1kfj said:
I technically haven’t made any changes to the stock wiring harness besides connecting the power trigger to the radio trigger wire. I replaced the stock distributor with a DS2 so that everything could be put back to stock points if need be. I’ll have to work on posting pictures

:hmmm: Glad you finally got it to work, you kind of took the long way around to get there, using the Radio wire as a trigger isn't going to work for an ignistion power source at least not with the stock Ford wire harness. With the stock wiring harness the Radio circuit is only powered when the key is in the On / Run position or when the key is in the Accessory position, but there's no power going to the Radio circuit (and most if not all of the other fused circuits for that matter) during engine cranking / starting. Best of luck on your pickup. (y) :nod: Edited
 
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