Vintage Mustang Forums banner
1 - 17 of 17 Posts

·
Registered
Joined
·
729 Posts
Discussion Starter · #1 ·
Duraspark 2 box, standard blue streak coil, cap, and rotor. Spectra premium distributor with steel gear for the roller cam.

When I turn the key to start one of three things happen.

1. Engine starts and stumbles when key is released but catches and runs fine after.
2. Engine turns over but no start. Doesn't even try to fire.
3. Engine turns over but only fires when key is released. If I have my foot on the gas I can usually catch it and it starts and runs fine after.

On a whim I turned the key to the 'on' position and jumped the solenoid battery post to the 'S' terminal and the engine started right away with no hesitation or stumble.

Am I right in thinking that the ignition switch is faulty?
 

·
Registered
Joined
·
172 Posts
Possibly starter relay. Check for ~12V on the I terminal while cranking (ignition in start position). If not present, replace starter solenoid.
If above is present, check for 12V on the red/green coil wire. If present it should start normally. If not present, chase that red/green wire.
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #3 ·
12 v at 'I' post while cranking, drops back to 10.5 v while running. As I understand it, the 10.5 v is backfeed from the ignition box.

At the coil while idling, 10.5 v on plus side and 6.5 - 7 v on minus side. I'm using an aaw wiring harness and 1.4 ohm ballast resistor before the ignition box.

Today I got the car started and let it idle. As it warmed up it began to misfire. The fitech tried hard to keep it running but it finally died. Once I got it restarted I tried to rev it up a bit to see if it would smooth out but it started to pop and backfire through the exhaust.

The ignition box was warm and the coil was too hot to touch for long. I'm done messing with it today but I think maybe tomorrow I'll pull all the duraspark stuff off and put the pertronix dizzy and coil back in and see what happens.
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #5 ·

·
Registered
Joined
·
38,218 Posts
From where are you supplying the RED and WHITE wires of the DurasparkII module?

The RED wire should be connected to your ignition switch "C" circuit ("hot" when key is in "ON" position only).

The WHITE wire should be connected to what used to be the "bypass" or BROWN wire from the starter solenoid "I" terminal.

My guess is that the power is being dropped on the WHITE wire when cranking. This could be due to a bad solenoid or wiring issue.
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #7 ·
Red wire is paired with the ignition wire from the key switch on the unresisted or hotter side of the ballast resistor. White wire runs to the I post on the solenoid. I get 12v while cranking at the I post.

Honestly it seems like the ignition switch has a dead spot in it when releasing the key from the start position. At times the accessories won't work without wiggling the key in the switch.
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #8 ·
Well, after a false start I ordered a new ignition switch from aaw. It'll probably be a few days before it gets here but in the mean time I had a couple of ideas that I wanted to try out.

First I fully charged the battery. It wasn't really low but I wanted max voltage to start with. Then I snipped the switched 12v wire to the fitech and jumpered it directly to the battery post on the solenoid so it would get a full 12 volts no matter the ignition switch position.

Engine started right up and idled pretty well until it started to warm up. Then I could hear a miss at idle and if I tried to rev the motor it would stumble and backfire through the exhaust. I could take the rpms up slowly to a certain degree but if I goosed it, it would stumble and pop.

So I shut the engine down and tried my second idea. I jumpered across the ballast resistor giving the coil a full 12 volts while running. Engine started right up and didn't miss a bit through the entire rpm range.

The coil I'm using is a standard blue streak FD-476 cannister style coil. While the printing on it says 12v 1.5 ohm resistance every bit of info I could find on that coil said to use a ballast resistor with it.

I also looked at my old pertronix flame thrower coil that I ran 12v to for years and it also has 1.5 ohms resistance so I'm thinking that I can probably safely eliminate the ballast resistor as well as the wire at the solenoid I post.
 

·
Registered
Joined
·
38,218 Posts
Well, after a false start I ordered a new ignition switch from aaw. It'll probably be a few days before it gets here but in the mean time I had a couple of ideas that I wanted to try out.

First I fully charged the battery. It wasn't really low but I wanted max voltage to start with. Then I snipped the switched 12v wire to the fitech and jumpered it directly to the battery post on the solenoid so it would get a full 12 volts no matter the ignition switch position.

Engine started right up and idled pretty well until it started to warm up. Then I could hear a miss at idle and if I tried to rev the motor it would stumble and backfire through the exhaust. I could take the rpms up slowly to a certain degree but if I goosed it, it would stumble and pop.

So I shut the engine down and tried my second idea. I jumpered across the ballast resistor giving the coil a full 12 volts while running. Engine started right up and didn't miss a bit through the entire rpm range.

The coil I'm using is a standard blue streak FD-476 cannister style coil. While the printing on it says 12v 1.5 ohm resistance every bit of info I could find on that coil said to use a ballast resistor with it.

I also looked at my old pertronix flame thrower coil that I ran 12v to for years and it also has 1.5 ohms resistance so I'm thinking that I can probably safely eliminate the ballast resistor as well as the wire at the solenoid I post.
The original "yellow top" coil ALSO had 1.5 ohms of primary resistance. Beware that with the increased dwell of the solid state ignition and increased voltage that your coil's oil bath may not be able to control the additional heat.

Something to consider, when you apply OHMS LAW to the circuit...

Assuming 14.2vDC while running, 1.5 ohms of circuit resistance will equal a current requirement of 9.4667 amps and will generate 134.42667 watts. Ever touch a 100-watt light bulb? At 3.0 ohms circuit resistance, your amperage and wattage is cut in half.
 

·
Registered
Joined
·
94 Posts
From where are you supplying the RED and WHITE wires of the DurasparkII module?

The RED wire should be connected to your ignition switch "C" circuit ("hot" when key is in "ON" position only).

The WHITE wire should be connected to what used to be the "bypass" or BROWN wire from the starter solenoid "I" terminal.

My guess is that the power is being dropped on the WHITE wire when cranking. This could be due to a bad solenoid or wiring issue.
Actually the white wire should be connected to the start terminal so it is only powered during cranking. The i terminal will still have power when running but at reduced voltage.
 

·
Registered
Joined
·
1,136 Posts
Another thread about ordering an ignition switch from AAW... Are the AAW switches wearing out early? If you order a new one, perhaps open up the old one to see where the wear issues are.
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #12 ·
Well, I received and installed the new ignition switch today and while I no longer have to wiggle the key in the switch to get the accessories to work the engine still won't run unless I bypass the ballast resistor.

The engine will fire in the start position but as soon as I release the key to the on position it quits unless the resistor is bypassed.

I'm not sure what to look at next. On the few occasions lately that I've been able to get it running without bypassing the resistor I've had 10.5v on the (+) side of the coil and 6.5v on the (-) side, which I think is what it should be but even with those voltages it still misses and backfires.
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #13 · (Edited)
I'm done messing with this thing. Today I pulled all the duraspark CRAP off my car and put the pertronix distributor and flame thrower coil back in.

In skimming the pertronix instructions I see that they specifically say not to use any kind of resistor when using their 1.5 ohm flame thrower coil.

Anyway, it starts right up now and runs great. Why the duraspark system worked ok for 3 months with the ballast resistor wired in and then suddenly wouldn't run unless it was bypassed, I don't know and frankly don't care.

Screw duraspark.
 

·
Registered
Joined
·
38,218 Posts
I'm done messing with this thing. Today I pulled all the duraspark CRAP off my car and put the pertronix distributor and flame thrower coil back in.

In skimming the pertronix instructions I see that they specifically say not to use any kind of resistor when using their 1.5 ohm flame thrower coil.

Anyway, it starts right up now and runs great. Why the duraspark system worked ok for 3 months with the ballast resistor wired in and then suddenly wouldn't run unless it was bypassed, I don't know and frankly don't care.

Screw duraspark.
DurasparkII uses a ballast resistor to the coil, not to the ECU. The RED wire to the DSII box needs a clean 12V.
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #15 ·
DurasparkII uses a ballast resistor to the coil, not to the ECU. The RED wire to the DSII box needs a clean 12V.
Yep, that's just how I had it. I had the ignition wire paired with the red wire on one side of the ballast resistor and the pink wire on the other running to the (+) side of the coil.

The attached PDF is the aaw diagram that came with their duraspark harness and I followed it to a T.
 

Attachments

·
Registered
Joined
·
38,218 Posts
Yep, that's just how I had it. I had the ignition wire paired with the red wire on one side of the ballast resistor and the pink wire on the other running to the (+) side of the coil.

The attached PDF is the aaw diagram that came with their duraspark harness and I followed it to a T.
How a "stock" DurasparkII system is wired....
803542
 

·
Registered
Joined
·
729 Posts
Discussion Starter · #17 ·
How a "stock" DurasparkII system is wired.... View attachment 803542
That's a diagram that I haven't seen before and that's part of the problem. I'm not discounting your diagram or experience Bart. It seems like everybody and their brother has a Duraspark II wiring diagram and they're all different.

You know what's simpler and less expensive? Putting in a Pertronix distributor, attaching the black wire from the distributor to the (-) post on the coil, attaching the red wire from the distributor along with the ignition wire to the (+) post on the coil, turning the key and going for a drive.

No extra wiring to clutter up the engine compartment, no ballast resistor, no ugly gray box, and no connectors that look 3x bigger than they need to be.

And, importantly, no frustration with trying to find the 'correct' wiring diagram. I'll probably pick up a spare pertronix module to keep in the glove box and maybe a spare coil to put in the tool bag in my trunk because really that's about all that can go wrong with it.
 
1 - 17 of 17 Posts
Top