I have a '85 F250 4X4 with a 351W I am converting to a Duraspark II ignition. I haven't been able to go to the junk yard to pick up the wiring harness needed. After reading and looking at several wiring schematics it seems like will be fairly simple to make a wiring harness. I know it would be easier to go to a junk yard and get a wiring harness but their hours don't mesh with my off work hours. My question is, I need a wire that can provide 12 volts when the ignition is in the start as well as the run position. I did some checking and testing of wires in a wiring harness under the hood on the drivers side wheel well/cover. I found 6 wires that kind of fit the requirements, they are as follows. Red or Orange with Yellow Dashes approximately 14 or 16 gauge, Dark Green with Yellow or Light Green Dots 14 or 16 gauge, White with Blue Dashes/Slashes 14 gauge, (Hot) Pink with Green Stripe 8 or 10 Gauge, Brown with Pink Stripe 8 or 10 Gauge, Red with Green Stripe 8 or 10 Gauge. The 3 large wires all come together in a sealed connector and the Red with a Green Stripe is the only wire that continues on. I used my meter to check the voltage on all 6 of these wire and they all have 12 volts in the ignition "run" position. When I turn the ignition to the start position, without depressing the clutch the starter doesn't engage and all 6 wires still have 12 volts. When I actually engage the starter the voltage on all 6 wires drops to 10.5 volts. I am going to install the Duraspark ignition module with the blue wire relief and am wondering if any of these wires will work to power the ignition module with the 1.5 voltage drop during starting? If any of these wires will work to power the ignition module I would appreciate a recommendation on which wire to use, smaller or larger? Thank you for your input, thoughts, suggestions, and for sharing your wisdom.

 

12ga wire will be fine to the DS2 system. On the run wire going to the coil you must have a ballast resistor in line to limit the coil's current so it won't burn up. The start wire just bypasses the ballast so the full battery voltage(voltage will drop when the starter is engaged to about 10V on a fully charged battery, thats normal) is applied.

THe ballast is usually part of the wire harness inside the dash, its a special resistance wire. I just get a ignition ballast resistor from a parts store and mount it on the fender.

There are afew writeups for the DS2 swap complete with wireing diagrams if you do a search for it.

 

What did your truck have before? All the wires should be there already, including the resistance wire in the harness. Most of the time the duraspark module just plugs in to the plugs already there.

 

Thank you Eddie I appreciate your input. The ignition system my truck has now is the "computer" controlled distributor. The distributor doesn't have a vacuum controlled spark advance all it has is several wires coming out of the distributor where the vacuum advance is on a DS II distributor. It has been recommended in another thread on here that I convert it over to a DS II distributor. I am sure the connectors are there to connect the wiring harness so I can connect the DS II ignition but so far I have been able to locate them. My thinking is I can use the same wire to supply power to the coil that is currently being used with the old ignition system. I understand the coil wire has a resistor wire in it and I can splice into that wire before the resistor section but with it being under the dash it has been hard to locate with out disassembling the dash which I would rather not have to do. I can get the "hot" in start from the starter solenoid for the white wire on the ignition module and hopefully power the coil with the existing coil wire so that only leaves me needing the "hot" in run and start for the red wire. As I was saying I have located 6 wires that I think/hope will work to power the red wire. If I can use one of these wires I have located then I won't have to locate the wire under the dash. Is my thinking correct gentlemen? I am thankful for your input and appreciate any thoughts, suggestions, and ideas you share with me.