Stupid duraspark

[ugly74]

Hello everybody!
I’m having problems with my blue connector duraspark module.
I installed this with my 302 years ago, when my unilite took a dump, and it never missed a beat.
I just re-installed my 351c, and I simply robbed the guts from the 302 dizzy and put them in the Cleveland dizzy, and ran the duraspark like before.

Then the module failed. It would spark only right as I was switching the key off, but not as it’s cranking.
I replaced the module (Autozone part) and wired it up, but this time added a 1.3 ohm resistor between the module and + side of the coil. (Never had one before)
Fired right up! Sweet!
It ran for about 20 minutes, then I took it for its maiden voyage. About a mile down the road, it did it again. Module is hot to the touch, and it only sparks as I’m turning the key off. Same as before.

It’s wired the exact same way it’s always been (except now with a ballast).

Can one of you gurus lend me some clues?

 

[Broncobowsher]

What coil are you running? Is the coil overloading the module?
Operating voltage? A stuck regulator might be blasting the module with too much voltage?
Or you are finding the crap that is the quality of today's new parts.

 

[ugly74]

It’s a Mallory coil I had been running with the unilite. I’m getting 12 volts to the coil+, and that’s where I’m sourcing the power for the module. I wouldn’t doubt it’s just crap parts, but the one failed shortly after this swap, and then the 2nd one didn’t live 1/2 an hour, with the same exact type of fail. That’d be uncanny.

I’m still trying to arrange for a helper in getting her back home so I can fiddle more.
I’ll test the coil and distributor end to see what else may be awry

 

[WheelHorse]

Might not be a bad time to do the HEI module conversion...wire it in place of the duraspark module and to a heat sink of course.

Some guys swear by it.

 

[SHX669]

Duraspark ignition coils don't "run" on 12 volts they have to have a resistor so maybe there is a mismatch there - and ypu're powering the module off of the coil ???

 

[ugly74]

Might not be a bad time to do the HEI module conversion...wire it in place of the duraspark module and to a heat sink of course.

Some guys swear by it.

In my googlings of duraspark fails, I saw that mentioned a couple times. Seems simple enough, with plenty of spares to be had.

 

[ugly74]

Duraspark ignition coils don't "run" on 12 volts they have to have a resistor so maybe there is a mismatch there - and ypu're powering the module off of the coil ???

I’m sourcing the power from the hot side of the coil, yes. I didn’t before, but I do now have a 1.3 ohm ballast in line. It didn’t help!

I finally got it home, it hadn’t even made it to a paved public road. Neighbor came to help me pull it, but I turned the key, it fired up and drove home.
Raining pretty good, I’ll test stuff later.

 

[ugly74]

Tested the coil, and it’s good.
Tested the pickup and it’s good.
And i am getting 12.63 (battery voltage)to the coil and to the module. The ballast is only ohming at .9 ohms now, but it was 1.3 before I installed it. Getting 12.63 on both sides of it.
It’ll be a few days before I have time to let it just run and sit till it dies, so that I can check and see what’s what

 

[Jdgephar]

Kinda sounds like the ignition key switch might be bad. Can you measure the voltage to the module and see when or if the module is actually getting power when it dies?

If you added the resistor, you have to make sure the module is is before the resistor so it gets 12 volts, and the coil is downstream of the resisitor so it gets the reduced voltage.

Also, since the engine isn't running, and coil isn't grounded, you have no current flow, so it will measure 12v anywhere. Once current flows with the engine running, then you will see the reduced voltage at the coil. Thr current flow may also be what overheats your ignition switch and causes the module to lose power.

You can also build a small test jumper to bypass your ingition switch. Make sure to put a fuse on it, and you can run it right to the battery. Dont leave it this way with the engine off for long, because it could leave your coil running depending on where the distributor stops. But it will get you home if it dies somewhere (assuming the issue is the ignition switch).

Sent from my SM-G950U using Tapatalk

 

[jckkys]

The Duraspark module has specific needs in terms of voltage, IE it needs a 1.10 ohm ballast resister. The correct coil has a 1.17 primary and 8.500 ohm secondary resistance. After market ballast resisters and coils need to posses these values. I only use NOS modules made by Motorcraft in the '80s to be sure they're US made. One I've run for 30+ yrs. with no problems. Another is still in the Motorcaft box. You can always downgrade to the GM system too.

 

[SHX669]

There are multiple schematics on the internet on how to wire a dura spark it's fairly easy . I wired mine and had no issue with the DS system at all .

 

[DirtDonk]

Since you are now also powering the module from the coil (why is that by the way, when you had it working for many years before?) why did you put a resistor in-between them? Is the resistor actually in the power line leading to the coil, or is it literally between the coil and the module?

Neither one should be correct for a Blue Grommet module by the way. At least not as far as I know.
The coil needs the resistor between the ignition switch and the positive side of the coil, but the module gets the full 12v unless you have one of the 7-wire variety with the Brown wire (I forget what color wire strain relief those were though) where the Brown wire gets a 1.3 to 1.4 ohm resistor.
Otherwise the coil gets the 1.1 ohm resistor jckkys mentions, but not the module.

Are you also running the START signal to the other wire, or just running the single power wire to the module?
Are you still running with the radio noise suppressor on the positive side of the coil?
If you are running the noise suppressor, and if you are running the START signal from the "I" wire post on the starter relay, temporarily disconnect both of them while testing.

If that bit about the resistor and the module sounds wrong jckyys, let me know. But that's what I have always seen in the diagrams. Only some models of the Dura Spark module got a resistor.

But in this instance, does a resistor lowering power to the module help or hurt it? They get pretty hot in normal use anyway, correct? Is it more likely to run hotter with a resistor inline, or cooler?

Paul

 

[gr8scott]

Your thread title says it all ugly74. I will never downgrade to duraspark ever again, way too many failures for me.
Here's how I wired my HEI module. Right now it sits on my fender apron as a backup ignition to my MSD digital 6A.

 

[Broncobowsher]

HEI modules are so simple. They do need a heat sink to stay cool. I've heard of them installed inside a duraspark housing.

 

[ugly74]

Since you are now also powering the module from the coil (why is that by the way, when you had it working for many years before?) why did you put a resistor in-between them? Is the resistor actually in the power line leading to the coil, or is it literally between the coil and the module?

When I first installed the duraspark years ago, I sourced the power for the module at the coil+, it never occurred to me to find a different source. It worked for a long time! Only when this module quit, did I read a bit more and that some (but not all) modules were to be ballasted. So, it wasn’t until yesterday that I wired one in. I must’ve misunderstood, in that the coil needs to be ballasted, not the module. So this morning I yanked it (the ballast) back out.

Are you also running the START signal to the other wire, or just running the single power wire to the module?

i do have the white wire from the module tied into the start signal at the relay, yes. I figured that’d let me run a touch more initial timing without making the starter angry.

Are you still running with the radio noise suppressor on the positive side of the coil?

Uh, no? I have there’s wire from the module, and the red/green stripe hot wire from the ignition switch to the + side of the coil, and thats it.

If you are running the noise suppressor, and if you are running the START signal from the "I" wire post on the starter relay, temporarily disconnect both of them while testing.

I think my tests this morning I’ll leave it all hooked up as is (sans ballast), drive it around real local like, and when it shoots craps, break out the meter and see what I got.

But there’s a delay! I found that my upper rad hose was hitting the PS pulley a bit, so I’m going to go get a shorter belt for it first.

 

[ugly74]

Tryin to chop up a text so it’s all separated with proper quotes, on a newfangled smart phone is a pain in the dick

 

[Jfryjfry]

Echoing an earlier post, the ignition switch sounds suspicious. I have had two aftermarket switches show similar symptoms

 

[ugly74]

Why the switch though? I still had power at the coil in start and run, and power to the relay at the appropriate time too.

 

[broncogt]

Your thread title says it all ugly74. I will never downgrade to duraspark ever again, way too many failures for me.
Here's how I wired my HEI module. Right now it sits on my fender apron as a backup ignition to my MSD digital 6A.

Looks like the coil is 12 volts at all times. I have my coil being powered by the stock ballast wire during run.

Am I doing it wrong?

 

[SHX669]

Assuming you still have "factory wiring " and not a new harness - I think at lot of your issues will disappear if you find one of the Duraspark wiring diagrams and wire your module , distributor and coil in that manner.
It's been quite a while so I don't want to go just from memory and then steer you wrong with " remembering" what wires get hooked up and where - but Duraspark coils don't have 12 volts when in the "run " position . The coil + is wired from the factory resistor wire while in the "run/on " position. At startup {only } the resistor wiring is bypassed and the coil gets a full 12 volts.
The red and White wires on the module are power wires . One gets connected to the start circuit and the other to the "run " circuit.
The other wires connect to the coil and the distributor - like I said I won't try to remember which as the wiring schematics are a better source of info than my memory .