Duraspark Resistor

[85_Ranger4x4]

I have been having a nagging issue of burning up the factory e-coils and DS modules in my '85 and have been doing some digging around on possible causes. One thing I noticed in my '85 service manual for the 2.0L (which ran Duraspark) is it had a "ballast resister" feeding the coil. This is the same drawing that is in my '85 shop manual.

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In the shop manual it says it is actually a resister wire and not to cut or splice it. For the 2.8 it shows no such "ballast resister" feeding the coil, just straight 12V. My '85 EVTM collaborates this and adds that it is a length of 1 ohm resistance wire for the little four banger.

Mine is getting the full 12V now and I wonder if it is causing some kind of feedback issue between the coil and module thru the tach wire.

Anywho I was digging thru the BWD Ignition and Electrical catalog at work and found they show a BWD RU13 single pin one wire resistor wire that fits Fords 60-68 and 70-96. 61" long pink in color and 1.35 ohms for a price of $31 (O'Reilly's website). Poking around online and other 80's Fords with Duraspark had a pink resistor wire feeding the coil. My catalog also shows a ceramic version BWD part number RU6 that is also 1.35 ohms and runs under $10 for a cheaper and easier to install option.

I have been getting a little over a year out of the coil and modules so it is hard to say right away if it is a fix or not, but they were there on the factory Duraspark setups and are not there in the non-factory Duraspark setups.

I bring this up because neither of the Duraspark articles really mention much about the resister, they show it in the wiring diagram but that is it. My initial train of thought was if the coil didn't need it to start with it isn't seeing anything different and shouldn't need one with Duraspark... but I am thinking it needs to be there.

http://www.therangerstation.com/tech_library/DurasparkII.shtml

http://www.therangerstation.com/tech_library/2_8Duraspark.shtml

 

[RonD]

Get the ballast style resistor, It should be mounted to firewall on its own, nothing touching it because it does get warm.

Ford started using resistor wires in the mid-1970's, pink and usually under the dash.
You do not want to double resistor the coil, lol.

The coil needs full battery voltage when starter motor is turning, but thats only 10volts.
After engine starts it should see 6-8volts max.

Tach is hooked to "-" side of coil so gets a voltage and Ground pulse both, distributor V6 gets 3 pulses per RPM
Resistor or no resistor shouldn't effect tach

But it can effect a module, lower coil voltage is also better for the transistors in the module that "act as the points" opening and closing Coil's Ground to power it up and then cut Ground to spark it

 

[85_Ranger4x4]

I just gave both options, the regular wire isn't worth $30 to me but it might be to someone else. The ceramic one will be very easy to add to my system.

EDIT: 04/30/18 - Ecoil is a no go, went to a oil filled can coil like the DS ignition was designed to have and all seems to be well.