I just recently converted my eec iv 4.9 truck over to dsII. got a wiring harness from a donor plugged it all up and truck fired up and ran good...........for about 5 mins. then shut off and wouldnt start again. coil was getting no spark. at first i thought it was the module fried because of a bad ballast resistor. but it all checked out ok. later found the coil got fried because its running 12 volts all the time. when the ign switch is in the run pos. its only supposed to have 6 to 8v. mine has 12 so i know what the problem is. i need to wire in a another resistor. ? is how do i do that but keep 12v going to the coil at start but not during run??

some people say you dont have 2 resistors, well yes you do. one is a big fat pink/ red wire that runs into the cab for the module itself. On my old eec iv ignition i had another factory wired resistor for the coil also. stupid me didnt wire one back in and blew the coil. but i need some help wiring a resistor in.

 

"On my old eec iv ignition i had another factory wired resistor for the coil also"

I would like to see a photo of the "other" resistor.

My truck only had the stock resistor wire that is bypassed with the key in the start position to give full voltage to the coil when the starter is engaged.

The stock wiring on a EEC IV system will combine 3 hot wires to feed the coil and other items. You will need to drop back to just the one wire, red with green strip on my truck, which is the fat one on the firewall side of the connector in the 4 wire plug on the left inner fender. This is a resistor wire to drop the voltage to the coil.

There are 3 plugs on the left inner fender, the one with 2 wires will power the DS2 module; the one with 4 wires will power the coil positive, oil press, water temp with one extra hot wire that you wont use; the third plug will have 2 wires and the green one is the feed to the tach.


More info here
https://www.ford-trucks.com/forums/7...-150-woes.html
posts #13 #16 #19

You should be using a older round coil with the DS2 as the primary resistance is not the same.

more info here
https://www.ford-trucks.com/forums/8...onversion.html

good luck

PS... the older trucks used a different starter solenoid to power the coil when the starter was engaged to provide full voltage to the coil when the starter was engaged. The "S" connection on the solenoid went to the coil POS connection.

Jim

 

If you had the TFI system(which I think you did with the EECIV), then you do not have the required resistor for the coil +, which you have already figured out.

Just go to the parts store and get a large white resistor for a Chrysler product. Mount it to a spot where it can stay cool and not touch anything that will melt, it will get warm while it's running.

Take the + wire off the coil and hook it to one side of the resistor. Take a wire and hook to the other side of the resistor, and hook it back to the coil +.

Like the other poster said, get a starter solenoid(fender relay) from a older vehicle that has 4 terminals. Hook it in with the wires you have now, put the large battery wires on and hook the original red/blue to the "s" of the new solenoid. Just make sure the large wire terminal that is nearest the little "s" terminal, is the one going to the bat +.

You will now have an extra terminal on the new solenoid labeled "I". Take a new wire and hook it to the "I", and then run it over and hook it to the + of the coil. That is your resistor bypass for starting.

 

i got a brand new solenoid for my 85 and it has an I terminal, no need for a new one from an older truck. it has bat pos terminal, s terminal for ign. I terminal which nothing is currently hooked up, and a starter terminal for the wire going to the starter.

 

I did this same conversion on my 1985, and the stock ballast resistor wire was already in my truck's original harness. I had to dig to find it, but it was there, it just sat unused because my truck used the TFI/EEC-IV harness.

 

Didn't know that, they must have used the same harness for different engine configurations. I wouldn't bet you can find this on every year truck though.

 

The reason why is this:

From 1980 - 1983, all F150s used the Duraspark ignition system.
All of these were designed to run on the Duraspark ignition. None of the 1980 - 1983 models used the TFI ignition, although some California models were Duraspark and computer-controlled during these years. The TFI/EEC-IV came later in 1984.

From 1984 - 1986, almost all F150s used the TFI/EEC-IV igniton sytem.
For example, if your truck is a 1985 model and it came with the 300, 302, or regular 351, you got the TFI ignition with EEC-IV engine computer.

However, if your 1984, 1985, or 1986 model came with the 351 H.O. or 460 (these two engines were never computer controlled in this generation), you still got the Duraspark ignition.

So (in every example I have seen) from 1980-1986, Ford made all the internal harnesses the same, and then just plugged in either the TFI/EEC-IV harness (and engine computer) or the Duraspark harness. Fortunately, the ballast resistor wire is located in the vehicle's internal wire harness, so you should have the stock ballast resistor wire in the original truck harness.

In other words, every F-Series truck from 1983 - 1986 is already pre-wired to accept either the TFI or Duraspark ignition, depending on which engine you got.

 

There is a White/LB hash wire in the TFI-IV wiring harness that combines with the Red/Light Green wire at the coil + terminal. Remove the White/LB wire and the Red/Light Green wire should power the coil at 6-8 volts.

The White/Light Blue wire is a ballast resistor bypass for the TFI-IV coil.

If you removed, (unplugged) the TFI-IV harness and got a DS-II harness and plugged it in it's place, you shouldn't have these problems unless something has been changed by a previous owner, or you have non-standard wiring. IE: like Lariat 1985's explanation. the main harness wiring, where the DS-II coil ballast resistor is located, wasn't engine specific.

correct.

If I'm understanding you correctly, it's actually it's the "I" terminal, not "S" on the solenoid that goes to the coil, but otherwise correct. This practice was dropped in 1979, and the ballast resistor has a built in bypass wire already in the harness for starting 1980 and newer.

Also of note. Replacement Solenoids have both terminals, even Ford Motorcraft ones. This is because the replacements can fit a plethora of different vehicles. But Factory Equipped solenoids may only have one terminal. The "S" one.

 

Yes, what they did was add a extra set of contacts in the ignition switch of these vehicles to bypass the resistor wire in the start position.

 

Glad you caught my mistake...

"I" is for the Ingition coil positive
"S" is for the Starter connection

Thanks Jim