I've got this 74 F100 w/390, and it has points. I want to upgrade to electronic, and the prefered setup would be the DS2 (blue grommet box).
Since some 74's came with electronic ignitions from the factory, does the wiring harness already contain the needed wires for adding the breakerless system? It would seem prudent for Ford to have made the harness ready to accept either type ignition system, since both were used. I know they did this on later (83-87) trucks that could have either the DS2 or TFI ignition depending on which engine was installed.

If these needed wires are present, even if an "add-on" harness is needed, it would make upgrading so much easier. Can anyone tell me if they exist, and if so, where to look for them?

I tried reading the wiring diagrams, but haven't had much luck in decoding it, in regards to this matter.

 

No, the points harness was different than the electronic harness. If you do go with Dura Spark stay away from both the 74 and 75 versions. Each of these used ICM's that were year specific and don't interchange with any other control boxes.
I did a search the other day for someone looking for the correct wiring harness for the coil/distributor (engine gauge feed) and couldn't locate any.
I understand you wanting to stay with Ford (that's why I'm somewhat stubbornly sticking with points on the Pumpkin) but you might consider a Pertronix ignitor setup. Uses your stock distributor and an easy two wire hookup, probably be cheaper than trying to convert to a DS II setup.

 

Darn. I was hoping the harness was shared, and simply used either a different engine harness or add-on for the electronic. I noticed a round plug, like the electronic system uses, under the hood, but wasn't sure what it's for. Since it's located right near where the box mounts, I thought *maybe* that was what it was for. Not sure what color wires go to it, as they're rather dirty...... Funny how nearly 40 years of use will do that.

As for the 74/75 boxes, I am aware of their uniqueness, and planned to use the 76+ blue grommet box.
Coil/dist wiring will be easy, since I am planning to use part of an engine harness from an 80-86, as it has all the correct plugs.

I've considered the pertronix, but having already had 2 failures of their systems, on this very truck, makes me a bit reluctant to try them again. NOTE: this was back in the early days of pertronix (early/mid 80's), so I'm pretty sure they've made huge improvements since then.

 

Actually it doesn't look like it would be too difficult to fab the needed wiring harnesses.
This is the simplest wiring diagram I found. DS II is the top diagram, the bottom one is a DS III.
I know the coil plug is, or was, available. Not sure about the dist. and control box plugs.

 

All you need to power the module is battery voltage in run to the red wire and battery voltage to white in start mode. The rest as you noticed, is plug and play. Plugs are available at NAPA. There naturally were none on my 66, so just ran two wires back to ignition switch.

 

Correct me if I'm wrong, but the coil + voltage is the same rather points or DS/DS2, by means of the resistor wire.
And the "I" post of the solenoid is only hot during cranking, so running a wire from it to the white of the DS2 *should* supply +12V only during cranking mode.

 

Correct. I alway's run them back to the ignition switch and two wires are just as easy as one. Just a thing I've gotten into the habit of..
I don't have a diagram of your truck, but if you have a three wire plug coming thru firewall, the feed you need is probably already there.

 

I fried a unilite conversion in '80 or '81 , I figured they must be craap .

Most of us old school guys give jump starts , need jump starts , take the battery out while its running so we can swap them , etc . This causes nasty electrical surges and your sparky boxes don't like um . High output chargers give dirty spikes also .

Most of the aftermarket stuff is OK if you watch out for spikes . A slow charge on a low battery is the way to go .

If your semi electrical literate then hooking up a DS2 is not hard and you can probably get the parts used for very little .

 

[quote=mikeo0o0o0;11754922]No, the points harness was different than the electronic harness. If you do go with Dura Spark stay away from both the 74 and 75 versions. Each of these used ICM's that were year specific and don't interchange with any other control boxes.

This reminds me of a question I've been meaning to ask: If I wanted to replace the EI Module in my '75 engine with a post-75 one (which has the 6 wires as opposed to 7 on the '75), what else would I have to replace? Distributor? Coil? Voltage Regulator? Or, to put the question another way, since that EI Module is unique to the '75, are those other ignition parts unique to that year also?

 

[quote=JoeHarbourJets;11780090]Coil and dist are the same. The wiring going into the module is a bit different, as you noted (6 vs 7 wires). Modifying the wiring, and swapping the box *should* be all that's needed to upgrade to the newer blue grommet (76+) box.

 

Yes, that's what I thought too re the coil and dist. The difference on the module wiring is that the post-75s do not have the "extra" blue wire on the harness with the red and white wire. But, contrary to what the part manufacturers will tell you on the installation instructions, the post-75 module (with the 6 wires), will not simply plug in to the ignition system harness and work. Guys other than me have tried this, and as far as I know, with no success. But, I think if the dist, coil, etc are the same, there HAS to be a way to get the post-75 module to work. I have a 75 module, but it would be nice to get the later model to work as they are so much easier to find and buy. I am going to get the wiring diagrams for 75 and 76 and figure this thing out, if it can be figured out.
Thanks

 

i put a 302 in my old mazda, and i added duraspark to it very easily.the original blue box off my 76 is what i used(put msd on the truck--even easier by the way)

i just used good weatherproof 1/4" spade terminals and colored tape as connectors although the 'pigtails' can be bought at a parts store. i had a good link to a diagram on bcbroncos.com? i think but if you google duraspark conversions you should find some simple diagrams.

on the mazda im running everything from switches, so thats where im getting 'key power' to a relay and then to the red wire, the white wire goes to the starter solenoid(not actually neccesary but it backs off timing for easier cranking.) one goes to the coil and the others to the distributor. as far as the distributor you can find a reman at a parts store(it will have a core charge too) for 40-50 bucks i think for a 76 year model.
the red wire should come out of a resistance wire which may be on your truck already? but the link i found states it should be between 0.8 to 1.6 ohms. i didnt run this on my lil mazda project and its working fine, but if i ever drive it any distance ill probably go to the shack and get some resistors to put inline.
heres a link i found quick Duraspark II Conversion Basics

its also easy to use a GM 4 pin hei module,be easier to hide,too and cheap lol

 

Pertronix anyone just a thought quick and easy