I fairly recently acquired a 1985 F250 with a 4.9. The truck originally had the feedback carb system. I switched to Duraspark distributor as soon as I could. The truck has had a front clip swap so there happened to be a Duraspark II module still bolted to the fender liner. I hooked this up to power, distributor, and coil negative. For coil positive I am using the same wire that powered coil positive with the original ignition system. I am using the E Core coil that was already mounted to the engine. This setup gave no trouble for a couple of months of increasingly regular driving.

This week I cranked the truck and it would not start. I found no spark. While I was fiddling around with things under the hood I gradually became aware of a crackling sound, which I traced to the coil and yanked the wires out of the coil to stop the fire. Indeed after that event, a resistance test on the coil read open. Ok, I had a spare coil (used, also E Core) sitting around, so I bolted that up. I also tossed in a spare module (MOTORCRAFT blue grommet), thinking the module had shorted coil negative to ground, which burned down the coil. Oh well, old module, I was expecting it to fail anyways. I measured 7kOhms (hopefully I recall this correctly) to ground on the module’s green wire. Didn’t seem like a direct short to ground, but not exactly open either, so I chucked the old module and ordered another new one for a spare.

Two days later the truck starts idling worse and worse all day, and finally will not idle. Eventually it stalls and will not fire again. I find again no spark, and pretty quickly the coil is letting out a vigorous crackle and plume of smoke.

This time I measure resistance to ground on the green wire and find 134kOhms, so this module does not appear to be shivering coil negative to ground. However, I also noticed that when the key is on, and either coil positive or coil negative is disconnected, and I touch that wire to its terminal on the coil, there is a pretty significant spark arcing from wire to terminal. I am thinking there should not be a complete circuit at that time, as coil negative is not grounded. Maybe I am wrong in presuming the spark is not normal?

At any rate, I was able to walk to an auto parts store and grab a replacement E Core coil off the shelf to get me home. The coil was fairly hot to the touch when I got home.

I have 12v at coil positive. Most of what I have read says that an E Core can run at 12v. However, there are some discussions stating that perhaps the TFI module reduces the dwell time to compensate for the higher voltage. Maybe the E Core really does need a ballast resistor when used with a Duraspark box? I wonder how I was able to run so long without a resistor? Was my used coil just closer to the end than the one that was on there before (what was there before was Blue Streak brand)?

Any thoughts on why these coils are burning up, and what I need to do to fix it, would be most welcome! I will post any further observations or testing.

 

Here's a link to help you learn how to test an e coil, jump to about 12:30 on the video for the e coil info.

https://fordmasterx.com/ford-ignitio...pecifications/

You do realize you're using the wrong coil for a DS2 ignition module.
I used a GM 4 pin module with my original e coil, as I didn't want to go back to a round coil. I also had plenty of old used GM 4 pin modules on hand. So the only thing I had to buy was a DS2 dist.

Bottom line is when you half the coil primary resistance and double the supply voltage, you get a times 4 increase in the current flow. Personally I would have expected the DS 2 module to fail first.

The DS 2 ingition system uses a match set of components, any changes reduces reliability. You will need to educate yourself more if you want to run in experimental mode.
good luck
Jim

 

Thanks for the reply. I must have found some misleading info about converting to DS2. Or maybe I confused info about DS2 module with GM module conversion info. To clarify, I should be using an old-style canister oil-filled coil with a ballast resistor if I’m using a DS2 module?

What characteristics does the GM module have that makes it suitable for use with the E Core?

Thanks,
Luke

 

Jim beet me to it about the wrong coil.
I dont think you have to run a resister as the wiring I dont think changed between feed back and non feed back trucks.
I would just install the round coil and call it good.

As for the GM part I dont know so cant answer that question.
I know my son is using the GM part on his Jeep and stll has the DSII as a back up.
Why he wanted to run the GM module I dont know. It is his Jeep so I let him do what he wants to it.
Dave -----

 

Yes, DSII box requires a resistor and the DSII coil. The DSII coil will have pins and takes a special horseshoe connector you can buy new or find in the junkyard.

The GM module has internal circuitry that limits the inrush current. So it does not need a resistor and can also run the square coil. You must mount it on a heatsink though.

You must have a very good DSII box. They usually smoke before the coil does in this situation.

 

The correct DS2 coil is a round oil filled one that has the "nail head" connection to match the snap on "horse shoe" stock coil connector.

Info regarding the GM 4 pin module here...

https://www.ford-trucks.com/forums/1...-failed-3.html
Starting at post 22, the thread was updated with a "it don't work anymore" comment.
So I really can't recommend it anymore as newer parts (GM 4 pin module) might not be compatible with a DS2 distributor wave form.
Will post more info later.
Jim

 

Thanks to all for the education in coils and modules! I’m thinking the modules probably are going first, then shorting the coils to ground. The coils are going up in smoke in quite a sudden fashion. I also found that my ground wire from the module to the distributor is burnt at the end. So this appears to be a ping pong effect of failures where the wrong coil destroys the module in such a way as to destroy the coil as well. I am off to the parts store now for an older style coil. Already have a replacement module in hand. I’ll try to remember to post back in a week or two if this is successful!

 

First off, I really don't recommend using the GM 4 pin module over DS2 system.
The purpose of this post was to explain why I used it.

1) On my truck, and most likely yours, the resistor wire is bypassed by an additional wire. This was not shown on the schematics and you had to physically go and look for it. It was really unknown whether the resistor wire was still full length or shortened during the modification which added the bypass wire. The purpose of the bypass wire was to allow full voltage to the TFI ignition system. The GM 4 pin ignition module did not need a resistor wire and would work with full voltage.

2) The GM 4 pin module would work with my stock E core coil, which was already mounted and ready to use. Also I should add, I am really cheap, and prefer to use what I got. The E core coil is a better coil anyway.

3) It's almost impossible to find a wire harnesses at the junk yard need for a DS2 conversion. The GM 4 pin module is easy to wire up.

4) The DS2 ignition module will conduct current through the primary ignition circuit when you turn the key to the ON position. Which is why the coil will get warm/hot when you turn the key ON without starting the engine. The GM 4 pin module does not allow current flow with the key ON. The constant current flow causes components to get hot and eventually burn out if you leave the key ON. Especially if you don't have a ballast resistor or resistor wire in the circuit and / or you substituted a coil that has a lower primary resistance then originally used, such as the E core coil.

0n a DS2 conversion, the only way to know if your resistor wire is still doing its job and dropping the voltage to the coil positive terminal is to turn the key to the ON position and measure the voltage at the coil positive. In theory, the voltage at the coil positive should be 6 to 8 volts. The coil should also start to get warm. Which verifies that there is current flow through the primary ignition system during this test.

Hope this helps, there is a lot of good info on the GM 4 pin module in the link in post 6. But I still feel going this route is still operating in "experimental mode" which is why I mounted 2 of them on my truck. So I could quickly change to my "backup ride along spare".

I truly believe the stock DS2 ignition system is the best and most reliable. But in order for it to be reliable it needs a matched set of stock components, without substitutions.

Good luck, Jim

 

Jim, have you ever experimented with the polarity of the input wires going from the dsII distributor to the GM module? I found it ran better one way than the other, and my distributor cap looked better. I can't tell you which way it was, but I am thinking it has something to do with the GM module triggering on either the rising edge or the falling edge, and the relationship of this to the rotor position. In other words when the dist generates the A/C trigger voltage, there is a relationship between this A/C voltage and the rotor position, which is set at the factory mechanically inside the distributor. If you swap the distributor wires, you can move this relationship a half=wave. Of course with the advance of the distributor, the factory has to split this down the middle somewhat.

 

I am working my way through the link in Post 6. I do like the idea of not being able to burn up ignition components by leaving the key on. When I wired up my DS2 box and distributor, I found connectors online. I just built the harness out of trailer light wire. But the DS2 plastic connectors are terrible, very difficult to get apart, even though it does have the added bonus of not being able to mix up the wires. If it can be made to work, these would be multiple pluses to the HEI setup for me. Also, it appears the HEI modules are cheaper. And DS2 modules do quit without warning, even in stock applications. Best to have 2 aboard at all times, if you need a reliable rig.

Jim, why do you say the E Core is a better coil?

Also, do you guys agree that I have been smoking coils because my modules are shorting to ground? I am trying to decide if it might be dangerous to reuse them when they have had a chance to cool down. I have a new module in the box that I could return if I could reuse some of the ones I have had problems with. I am paying about $50 for these modules in a Ford box for reliability’s sake, only to burn them up.

 

No I never did try swapping the wires, I just followed the directions shown in the post 6 link. I do remember reading if it ran poorly to try swapping the wires as you suggest. It makes sense, I just never tried both configuration to compare.
Now that you can buy a HEI coil in cap distributor for under $60, all this stuff seems like a moot point. But then some folks want the truck to look stock.
Jim

 

Oh my….HEI in cap distributor for a Ford six for less than $60? That’s what I paid for my DS2 distributor. Would you mind sharing the source for those? I looked them up and found most at $120. Knowing what I know now about what an expensive headache acquiring, mounting, and wiring the right ignition components together is, even at $120, a one-and-done solution sounds like a bargain. I am tempted to order one and declare the DS2 distributor, three DS2 modules, and one can-type and two E Core coils casualties of a learning experience!

Any thoughts on the reliability of the HEI in cap distributors?

 

In post 2, I provided a link. There is a video I watched in the post, it's long but very informative. E core coils start at about 12 minutes in. He explained well the improvements in the E core coil over the round oil filled coils. He even talks about failures like you have seen.
I don't believe the ingition module is shorting to ground. It's mounted on plastic, the only ground is the black wire going to the distributor, which is why you found heat damage in the black wire. I believe excessive current flow cause the damage. Excessive current flow was caused by running 12 volts to the coil and having a lower resistance than normal in the coil primary.
The sparking and arking you found at the coil was caused by a breakdown of insulation of the coil windings, most likely caused by heat damage from excessive current. The insulation on the windings is very thin, think of a shellac paint on a copper wire. Something that could melt off and then cause a current flow to the frame of the E core coil. This was explained in the video also.
Point is the ignition module might be OK if the coil when first, as the spark to ground was at the coil.
If you want a different option you could try this...
https://www.ebay.com/itm/12582516871...0&gad_source=4

I don't have any experience with these, but they do seem like a good upgrade.
Good luck, Jim

 

Update on my situation: I wired up the new canister type coil with ballast resistor. Cranked but would hardly catch. Spark tester showed a dim flash—weak spark. The ballast resistor measured 4.2 Ohms, advertised to be 1.5 Ohms. I was seeing 3-4v at coil positive. I bypassed the ballast resistor and the truck fired right up. I just needed to get it home as it broke down about a mile from the house. I can neaten up the mess of wires in the morning. These HEI distributors are sounding more and more appealing. Clean = less failure points and easier to diagnose and repair when it does fail. This is a work truck, so doesn’t need to look stock, just needs to be reliable.

About the shorting to ground theory, I think I was a little mixed up on basic coil operation: the module removes ground from the coil, not offers it. I’ve been working on too many newer cars, thinking about fuel injectors and whatnot! Your explanation makes perfect sense. Too much current flowing through the circuit, burning up the insulation inside the coil as well as my ground wire. Maybe these modules are ok after all. Will be interesting to test. With a spare stowed behind the seat!

I will watch the video you posted, it sounds like there is a lot of good info in there. Thanks for taking the time to share your knowledge about this topic. I’ve learned a lot about ignition systems today!

 

A couple of considerations with aftermarket HEI:

Many are of suspect quality and durability, i.e. Fling Dung brand from China. Make sure you go with a quality name brand, not some white box special on eBay.

Make sure replacement parts are readily available. For example, the distributor cap and rotor are considered consumable parts and need to be replaced on a regular basis. Don't quote me on this, but I think most aftermarket units are based on a GM design, and can use standard parts available at any auto parts stores. Be careful not to get some oddball design that takes proprietary parts, which could turn into a major headache down the road.

Back to the Duraspark system: The fix is simple. Don't mix and match parts from two different systems. Whichever system you pick, wire it up per the original design. My '84 351W has the original Duraspark system and it works great. I carry a spare OEM module but have never needed it.