I got the duraspark ii to run but still need help.
I’ve been reading as much as I could and looking for parts to convert my 1986 F-150 4.9l with tfi ignition back to Duraspark II since this spring. I found a 1981 F-100 at a local “auto recycler” and was able to pull the non-feedback carb, vacuum distributor, DS2 coil, blue grommet module and the associated wires to all including oil and water sensor pickups. After reading the multitude of forum entries etc, cook book stories on cutting wires adding ballast resistors and wiring diagrams which were a little hard to follow once in the engine compartment, I set out last week to amputate the electronic brain and graft in my new ignition. What I found was that
-there was a direct plug in power supply with two wires to module-OK
-the harness wire from module to distributor came right out of 1982 donor
-the main plug (from engine side with 3 wires) from ’81 system matched the ’86 plug (from firewall four wires) and when plugged together I(amazingly)got a start and oil and water gauges working.(nothing before I plugged into this connector)
This was a perfect plug and play—not nearly as difficult as the blogs I have been tracking.
I’m concerned though. The thicker red wire with a light green stripe to the female from <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-comffice:smarttags" /><st1:stockticker>EEC</st1:stockticker> wiring is connecting in the plug harness to a male blade from a small red wire and delivering power to the donor coil. When I check voltage to that line with the ignition turned to on but engine not running it appears to be 11 or 12 volts. I thought the thick red wire with green stripe from ignition was supposed to be a resistor wire and I should be reading 6-8 volts.
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Won’t this 12 volt supply melt my coil? If this is the resistor wire, why is it reading 12 volts in what I think is the run position?
I’ve traveled a few miles in this configuration but am afraid my DS2 coil will go poof at some point. Would I be safe if I went back to the tfi coil or does it require 6-8 volts as well?
Thanks in advance for any help

 

I've been trying to tell people here for years how simple this is with these year trucks.

Check the power at the coil connector.

It should be 6-8 volts in run.

If it's not, and it's still 12 volts, check to see if you still have the White/Lt. Blue stripe wire connected to the Red/Green stripe wire somewhere. This was the Ballast Resistor bypass for the TFI coil. on the 4.9L

 

Will that bypass be between the plug and ignition switch? I read 12 volts at the plug-that's my concern. I looked real quick this afternoon and didn't see a white light blue wire in the first inch of the plug so it must be in the taped bundle coming out of the firewall. Then do I just snip and cap the white wire. Then if I cut that wire, do I run another wire from the "I" on solenoid to supply 12 during start-up?

 

According to the diagram, it is at the TFI Coil connector. So it should have already been removed when you swapped harnesses. However something is causing the 12v in run.

The white/Light blue wire is only hot in run so you shouldn't need a seperate start circut wire. This wire also powers the module, so you cant totally eliminate it. You just need to remove it from the Red/Lt. Green wire, if it's still connected. Be aware the white/Lt. Blue wire is connected to the Red/Lt. Green wire at the ignition switch before the resistor. This has to remain. You are looking for a connection after the resistor. Check all the wiring from the coil to the switch. Someone could have been in there before you as well.

Worst case you are going to have to wire in a ballast resistor, and start bypass wire for the coil, or risk burning your coil up. However it is supposed to be already wired in. This is confirmed by the factory diagrams.

Good luck.

 

The voltage drop at the coil + only will happen when there is current flow through the resistor wire... so check the voltage at the coil positive with the engine at idle. It should be lower than battery voltage.

more info on testing here
https://www.ford-trucks.com/forums/8...-problems.html.

 

Should be considerably lower than battery voltage. Between 6-8 volts with 7 being optimum. Engine running. If it's out of the 6-8 volt range then something needs to be fixed.

You can test the ballast resistor with a Ohm or multi Meter set to ohms as well, with the engine off. With the harness connectors disconnected from the ignition switch and the coil. Zero the Ohm meter, then Hook the Positive lead to the ignition switch side, and hook the negative to the coil side connector on the Red/Lt Green wire. (Your ohm meter may need longer leads to reach etc.)

There should be a 1.05 to 1.15 ohm resistance from zero continuity if the ballast resistor is working properly.

 

I love the help but I still haven't defined the problem.
I split back the tape cover another 10-12 inches and found that the red-lg thick wire came out of (what appears to be factory) a three wire splice with the red-lg a smaller red wire and another thick brown with pink stripe all bonded together in a hard rubber junction. I read 11-12 v above the splice in both the brown-p and red-lg wire(engine off in run) also same voltage at the red wire at coil. When Turned the truck on and took readings again at all sites and read about 10 volts which is still too high. By the way the coil does feel pretty hot after driving 10 minutes around town( warmer than anything naer to it on the block)I never got to a connection with the white blue stripe to the red-lg. That white blue stripe runs directly into the two power supply to the module. I guess I need to pull the dash and dig all the way back to the ignition switch. There must have been a method in the madness of bonding three wires into the thick red-lg supplying power to the coil line. What?
JimsRebel- I think you have an 86 like mine -how did you run reduced power into the DS2 coil?

 

The Brown with pink stripe is the Resistor Bypass wire for the start circut.

The Resistor wire is the smaller Red wire from this rubber junction back to another Rubber junction block further up the line toward the ignition switch.

When the truck is in the start position, Full voltage bypasses the resistor wire, via the Brown/Pink stripe wire. The Brown/pink wire backfeeds from the other side in run at a reduced voltage.

Yes, 10 volts is reducing the voltage, but it's still out of spec, slightly. What is the trucks charging voltage, If the truck is charging voltage is too high, it will also affect the coil run and start voltage. But we will get to that later.

It's good that you didn't get to it. That means that all of the TFI-IV harness was removed. This is a good thing.

The rubber junction block you found is one end of the ballast resistor. If you go farther up the resistor you will come to another rubber junction at the other side of the resistor wire. You found the one end of the resistor wire, now you need to find the other. The other side is inside the cab and it will have 5 wires at the other end. The resistor wire, Three Red/Lt Green wires and a Lt Green/Red stripe wire.

Yes, One is the Resistor bypass for the start circut, Brown/Pink, and the other is the resistor wire itself. Smaller Red/lt Green wire. The rubber junction is to help identify the resistor wire and where it ends. If you follow the smaller red wire back farther you will come to the other end that will also have a rubber junction.

You need to find the other side of the resistor wire, and make another voltage reading there, with the truck running. Compare the two readings, from both sides. The side of the resistor closest to the ignition switch should be a significantly higher voltage than the one side closest to the coil. Post your findings, and we will go from there.

 

Thanks
I guess this wasn't quite as clean a plug and play as first appeared. I'll try and dig back deeper and follow the red light green wire back to the next intersection. The red -lg wire is as large in diameter as the brown-pink if that makes any difference. The only smaller(?14g) wire is a red one in the threesome.

 

Right, usually the plug and play works great.

You have a seperate unforseen issue causing a problem.

Why voltage readings need to be taken from both sides of the resistor wire.

 

i have an 86 and got my harness out of a 83 and it all just plugged in and works great no problems only thing is i still need a carb off the same year or around that year anybody got one they want to get reid of or sale it thanxs alot

 

whats the purpose of this conversion? is it so that you can run a carb on a normally efi truck?

 

The main purpose is to get rid of a defunct EEC-IV/TFI-IV ignition and computer system.

EEC-IV/TFI-IV can be both Carb or EFI in origin, both computer controlled.

If the EEC-IV/TFI-IV system is in good working order there is really no benefit to changing anything.

If the EEC-IV/TFI-IV system is in really bad shape, missing or broken parts etc, makes the truck run very poor. Replaceing the system with the earlier DS-II design, saves money, is simpler, and easier to get parts for, and easier to diagnose and repair than more complicated system. This way the engine will run well again.

 

I also have about 10 volts at idle, 12 volts with key on and engine not running.
I am running the original stock square coil with a GM 4 pin module. the square coil normally has full 14.5 volts applied to it and the GM 4 pin module can work with this current flow.

Which coil are you running??

 

more info and photos of my truck here.

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