Anyone know of a source for the Duraspark I ignition module, it's the 7-wire module used on 74-75's, the Duraspark II went to a 6-wire module from 76 onward, i really don't want to upgrade to DSII if i don't have to, my three parts stores in town all stock a 75 module but they are 6-wire units and included in the box is a note stating "ford deleted the blue wire but the module will still work for your vehicle" well news flash to ford, no it will not, the note doesn't state why the blue wire was deleted or give any directions as to how to make it work, just that it was deleted, i installed all three and got nothing, no crank, nothing (truck still fires with my old module but it's on its way out) places like LMC, NPD and DC list the module for my application but after a phone call to them and a hands on look at the module on their part they too are 6-wire modules, even Green sales who deals in obsolete OEM and NOS ford parts took a look at their modules and all were 6-wire, same deal with my local ford dealer, so my options now are scouring my local salvage yard and searching on ebay or lastly just swapping over to the ubiquitous blue grommet DSII set-up, so i guess my question is three fold, 1) does anyone know of a source for this module other than junk yards and ebay? 2) why was the blue wire deleted and what function did it perform? 3) can the 6-wire module be made to work? sorry for the long winded post but i just wanted to be as thorough as i could, thanks.

 

Ditch the duraspark and install an MSD unit.

 

As far as I know, the difference between Duraspark I and II was how the coil was powered when the key is first set to RUN. Duraspark I shuts the coil off shortly after the key is set to RUN if the motor is not turning, while Duraspark II keeps the coil powered regardless. One problem with the first version is that shutting off the coil like that can lead to a problem known as "start after the spark" which means in rare instances, you can shut the motor off, wait a few seconds after the engine stops, turn the key to RUN and the motor will start without the starter ever cranking the engine. This is a problem and I wouldn't be surprised if this situation was the reason for the change.

That's the difference between Duraspark I and Duraspark II. However, your question was what the blue wire does, and I do not know if the blue wire is used for the coil shut-off function. That is to say, I do not know if the blue wire distinguishes the two versions. I am told the addition of a Zener diode eliminated the need for the 7th wire, but I haven't seen a schematic to verify myself. I've never seen a schematic for the internals of a 7-wire module. It very well may be the difference between Duraspark I and II; I'm saying I don't know until I have the facts in front of me.

I have a schematic that shows the blue wire coming downstream of the coil ballast resistor, meaning it ties into the same place as the positive coil terminal. I'm really curious as to why the 6-wire model won't retrofit into the 7-wire harness, because the 6 wires match up between the two versions. The blue wire in your harness would just be a no-connect. I'm unclear about two things in your post: (1) you said you tried "all three" - what does that mean? (2) you said "no crank" - does that mean the engine isn't even turning over? Cranking and firing are two different things. If this is the only aftermarket module you've tried, I'd exchange it for a different module.

 

fmc400, sorry for the confusion, i meant all three as in three different modules, napa, carquest and federated, engine doesn't turn over at all with the 6-wire modules, it's just dead, so obviously this "deleted" blue wire is needed, at least on my application, i'm just baffled as to why.

 

Wait a minute - you mean the motor doesn't even crank? You turn the key, and it doesn't even move? Let me know if this is the case, because then I have some ideas.

 

There is something wrong with the wiring on your truck if the new 6 wire module doesn't work. The Red/Green and blue wire on the truck are connected by a resistor, (1.30 to 1.40 ohms).

On the newer 6 wire DS-I module this circut is internal instead of external. It still functions the same exact way.

Check for continuity between the Red/Green wire at the coil, and the Red/Green wire at the DS-I connector.

Then check the Red/Green wire at the coil, with the Blue wire at the DS-I connector.

I believe you might have a break in the Red/Green wire between the module and Coil.

Testing would confirm or deny this. Then we can go from there.

 

Didn't catch that first time.

Do the checks like I stated in the first post I made, and follow up with this.

Check the Red/Blue wire at the ignition module, with it unplugged. Check for power at this wire, while someone tries to start the truck. Take precautions if the truck wants to start etc...

Then do the same at the starter solenoid. Same wires.

You should have power to this wire with the ignition switch in the start position, in park if automatic etc...

If no power, plug your module in and check the wires again, the same way.

Report back the results.

Also, try this with the seat belts buckeld. I know in 1974 the FMVSS had a stupid Idea of the Seat Belt Starter interlock, that prevented you from starting a vehicle without you or your passenger buckling up.

Not sure it was installed on pickups, but it's mentioned in the 1974 Truck wiring diagrams.

Appendix A to the Preamble -Response to Petition

 

That is correct, i turn the key and get nothing, as if the battery wasn't even installed, it's just dead.

 

Thanks for your input, if the rain stops today i'll get my meter out and run these checks and let you know what i find.

 

I don't believe the "no crank" condition has anything to do with your ignition module???. It should "turn over", even when the module is out of the truck???.

 

flcracker9 is correct; the ignition module itself should not prevent the truck from cranking. As such, if the truck won't even crank, something else occurs when this module is installed. Because the module power ties directly into the RUN and START signals from the key, I suspect a problem that is preventing START from getting power, at which point the starter solenoid won't make. Check what 81 mentioned, and report back. Depending on what you find out, I have some ideas as well.

 

What you say makes sense to me, it should turn over all day long regardless of the module but yet when i plug in the 6-wire module i get nothing, no crank period.

 

I posted my most recent reply before i read your response but you guys are absolutely correct, the module should play no role in the engines ability to turn over but in my case apparently it does, i bought my truck from the original 30yr owner, the wiring is all intact and unmolested so i'll proceed with testing and post my results.

 

I found these wiring diagrams in a fellow members gallery, you can see the blue wire in the DSI in 75 and the deletion of the blue wire on the DSII in 76, can you tell what the blue wires function was from this diagram?

75 wiring: https://www.ford-trucks.com/user_gal...d=5922&width=2

76 wiring: https://www.ford-trucks.com/user_gal...d=5923&width=2

 

Exactly what I think as well.

The Module is tied into the run and start circuts, the main path for the start circut is disrupted somehow, and it's finding a work around through the original modules blue wire, and the trucks harness blue wire.

Since the circut for the blue wire is internal on the new module, it leaves the blue wire on the truck harness disconnected. Leaving the blue wire in the trucks harness dead. The start circut can't find the workaround it was using and it wont crank with the newer module.

The problem lies in the trucks wiring. Question is where. The tests should help narrow it down.