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But properly done, a DS is no more complicated than anything else. About all it has that an MSD or Pertronix doesn't is the "start" circuit to boost the spark during cranking.
Two circuits. One full 12V during start mode, and one routed during run mode through a resistor. The resistor can vary in types, but essentially do the same thing.
Sorry for the confusion... the ballast resistor is in the DS schematic, and is not part of the "box", but the box does have a "start" input as well.
The ICM has a constant BAT VOLT supply (RED), the same in RUN and/or CRANK. The resistor BY-PASS is only used to make the coil momentarily hotter for an easier START. The WHITE wire retards IGN LEAD while CRANKING to make starting easier and to lessen wear on the starter motor.
The system is fine if it came OEM, but if retrofitting a older ignition system, PERTONIX II is much simpler (IMO).
Either FORD DS II ICM or PERTRONIX module is subject to failure, as are all automotive components. The MAIN PROBLEM(s) I have observed is incorrect application and/or install. Stay away from PERTRONIX I.
A Pertronix is probably a better solution for a "mostly stock" build, and even up into lower-end performance. Once you get past that, you can worry about timing stability at high RPMs and a host of other things.
If you have a racing type motor in your pickup, you need PERTRONIX III -
The resistor only reduced the operating VOLT to the coil, not the ICM. BAT VOLT was applied to the coil only @ START.
BTW - DS II was not introduced until the 1977 model year. All previous designs (1973/ ) were SOLID STATE IGN.
73/75 was Dura Spark
76/up was Dura Spark II
Main difference was the control box and bigger cap
I worked as a Ford mechanic in 75/76, worked at a local shop 76/78 replaced a lot of the black DS boxes on the 73,74,75 Ford Elite's, LTD's, rarely ever replaced a DS II blue box.
It would be easy to convert a DS to a DS II
Main difference was the control box and bigger cap
I worked as a Ford mechanic in 75/76, worked at a local shop 76/78 replaced a lot of the black DS boxes on the 73,74,75 Ford Elite's, LTD's, rarely ever replaced a DS II blue box.
It would be easy to convert a DS to a DS II
1973 TO 1976 was SOLID STATE IGN.
1976 used a blue strain relief ICM which was later replaced by the 1977/ DS II ICM . DS II (1977) also introduced the larger cap and the coil output got stronger over the years.