dura spark question

[gregaba]

My friend bought a 78 F-150 4WD 351M short bed off a farmers estate. Has not run in 10 years.
We got it running but it runs like crap, a good reason to park it.
I was trying to perk it up a little and the spark was real week, I mean I was surprised it would fire up and run like that.
Went to install a new module and the previous owner had made some change's.
He had cut off the red wire and capped it with a wire cap on the 2 wire plug and had the white wire connected.
I don't know much about the dura spark system, but what would be the reason to cut the red wire?
Any help will get you a free beer if you want to come to Oklahoma and collect.
Greg

[jmlay]

I’m far from a duraspark expert. The red wire supplies power to the module…

[gregaba]

Thats why I am lost.
I have not traced the wiring yet but am confused as to why this is running.I would think the white wire would be cut because all it does is retard the disto at start up.
Greg

[cleandan]

Greg, look into how an MSD box is wired into a Ford Duraspark system. You might find your answers here.
MSD has the schematics for a few different wiring methods.
1) MSD box all on its own, wired outside the factory wiring harness.
2) MSD box all on its own but grafted into the factory wiring harness. (Using the factory Duraspark plugs and wires)
3) MSD box wired in conjunction with the factory Duraspark system, effectively giving the option to run either system should one system fail... like a backup system.

The early MSD box users often ran both systems because they thought having the backup (Duraspark) was a good idea should the MSD box fail.

Does the truck have a factory tach?.. Or did it have an aftermarket Tach?
Sometimes people tried weird things to get the tach to work with the MSD box and ended up with a big problem after butchering the harness attempting different things.

[jmlay]

Based on the diagrams I have viewed, the white wire at the box retards the timing. One of the diagrams showed the white and red flipped at the plug. Perhaps it depends on where the red wire is referenced in the circuit. Or it is a mistake in the drawing.:

https://www.carbdford.com/fletch/tech/duraspark/duraspark.htm

[Chuck]

My guess would be they tapped into the red wire feeding the module to power the coil or some other key on device. The coil maybe because the resistance wire went bad. What powers the module now? Are the wires nutted back together? If the red wire was cut at the module someone could have ran a wire inside to a switch and back out again to the module as an anti-theft device. Try looking for evidence of other wires cut or out of place and that may help. Put a voltmeter on your coil, make sure you’re good there running and cranking. If the coil has been bypassed it could have got hot and become weak. If you need more info there is some below.

[gregaba]

The owner sent it to the sandblaster to blast the bed so I won't be able to check it out until it gets back home.
I did notice the rats nest of wiring on the truck but didn't get time to look at it.
Most of my tools are in my shop and the truck is quit a way's away from my shop.
I think it will have to have a new engine or at least a new set of rebuild heads as it has 3 dead cylinder's. the distro is not correct and frozen to the block as the original reason he had me look at it was to adjust the timing.
Thanks for the help.
Greg