Hello all. This is for an 85 F250 5.8 Windsor motor that I recently rebuilt. After reinstalling the motor in the truck I was unable to get any spark at the plugs. After reading about the various ignition types, I believe I have Duraspark 2. There's a computer in the cab and a module on the engine bay. I looked at the schematic and it looks like there is a resistor in line to the ignition coil, and measuring voltage at the ignition coil shows 9 Volts. I was able to get the motor to run without issues if I jumped the positive side of the coil with battery voltage. it seems that the computer and ignition module are working properly, because I assume I wouldn't be getting any spark at all if they weren't.

I have a few questions

What could be wrong such that I need to jump the coil with battery voltage to get it working?
Can I run the truck this way or will it damage something?
Is there a simpler / better ignition system that I can use that is older but not points? Is Duraspark 1 "better" (less electrical parts) or is it basically the same? The reason for this third question is that now that I have the thing all ripped down it might be nice to simplify the wiring and not have to rely on a computer module and ignition module -- though this may be a question asked in total ignorance.

Thanks for your help!

 

I have continued to read on this forum and elsewhere and am beginning to think that I have a duraspark III instead of duraspark II.

 

Whatever you have, it's obvious you are not getting power to the + side of the coil when you turn the switch. Verify this with a testlight or voltmeter, and if that is true, the next stop is the ignition switch mounted on the column under the dash.

 

According to the info in this link, you either have a duraspark II system or a EEC system. If you have the EEC system, you should have a ignition module mounted on the side of the distributor itself. If you have the computer system, but do not have the module on the dist and have the module on the fender, someone has been there and converted it over to a duraspark II.

Start & Ignition (Gasoline Engines) - Gary's Garagemahal (the Bullnose bible)

 

Franklin,

Thanks for the help. I don't see a module on the distributor; only 3 wires coming out of it. I do have a computer inside the cab, so maybe someone converted it to duraspark 2.
I can measure 9 volts on the coil when the truck is in the "run" position, but I haven't been able to measure it while cranking.
However, if the truck is running and I disconnect my wire to the battery +12V then the truck stops as fast as a dropped watch.

 

These trucks are bad about the ignition switch and key tumbler mechanisms sticking and not going back to the right place after starting. You might want to lightly wiggle the keyswitch after starting to see if it will keep running. After twisting it over to start, pull it back out of the start position, don't rely on it doing it itself.

 

I'll take a look. I think it's probably worth me reviewing all the ignition wiring. I'll post what I find.

 

I used to say it was fine to leave the vehicle running on 12v with a jumper wire, because I did it for a few months on my Bronco with the stock coil. But since then have heard that many people have also tried it and fried their coils! So I guess I was lucky, or something else was different from those that did not have such luck.
I would not do that with a typical stock replacement coil however, because the Ford factory original "mustard top" versions were considered very well made compared to most Chinese counterparts. So don't do what I do in other words.

I'm not sure what's going on with yours since you said you were able to measure 9v at the coil but it would only run with the jumper. Strange.
You might try measuring it while the starter is cranking too. Maybe it's going down too far once that load is applied. Perhaps the Brown "I" wire is not functioning, or your '85 might not even have it.

I had an '83 F150 with 302 and it had the beginnings of a computer under the seat that controlled ignition timing along with the carburetor having things like a throttle position sensor and air valve controlled by the computer. Pretty sure it still had a Dura-Spark type module on the fender and did NOT have a TFI module on the distributor. Sounds like yours, where just the three wires come out of the distributor.
Just for giggles you might check the trigger module inside the distributor. Should be the same reading as a regular Dura Spark II setup where you want to see between 400 and 800 ohms resistance between the Orange and Purple wires coming out of the distributor. The Black w/white stripe is just a ground between the distributor and module.

I'll have to find some pics of the old truck to make sure I'm not blowin' smoke and that it did in fact have an ignition module under the hood. Kind of a transition to computer control of things maybe.

Good luck.

Paul

 

You can look in this link and see the different versions Ford offered that year and for what particular engine size.

.Start & Ignition (Gasoline Engines) - Gary's Garagemahal (the Bullnose bible)

 

I looked around at more diagrams on this forum and discovered that the "I" post on my starter relay was not connected at all, and I could find no trace of the wire so I added one. This got the truck to start and then die when in run. I was able to determine that my 9V was basically dropping off under load (which caused the truck to die) and was able to trace it back to a bad connection. After I repaired the connection the truck appears to start and run normally. Thank you everyone for your help!

For clarity, I believe the fender module I have is actually duraspark II. The ECM in the cab that I have was a red herring, and the previous owner must have downgraded to duraspark 2 but left the computer. When I removed the ECM it made no difference whatsoever in the truck's ability to run. So hopefully that's it, and it will continue to run.

Thanks again.

 

Thanks for posting back what the issue was as it may help others.
Dave ----