Ingition Woes - Mallory Unilite

[monsween]

Sorry for the first post being a problem but i've been having difficulties with the ignition system on the car. 

From what i've read so far the system is wired up correctly and I purchased the car set up like this.

 

Mallory Unilite 47639...?

Petronix Flamethrower 3 ohm coil (New)

Leads (New)

Plugs (New)

 

Battery voltage is running fine at >14v however i'm only seeing 6v at the coil?

 

It's not helping that i've an overfuelling Edelbrock 1405 carb on there however the car was fine for 1000miles or so before starting to misfire after 10miles or so.

 

Car is wired up with a ballast resister and condensor. 

 

Any ideas as to why i'm getting such low voltage through the coil and i'm presuming that's why the misfire starts after a period of time. (Measured across the +ve and -ve)

 

Edit: Forgot to mention those photos are of the old coil

 

Edited May 12, 2015 by monsween

[Zed Head]

Since you're seeing 14 volts at the battery, you must be measuring while the engine is running.  The ballast resistor is designed to drop voltage.  I think that six volts is about right for the early points type 240Z's.  What you see with the engine running is a composite of the off voltage and on voltage.  Basically you're measuring DC voltage on a pseudo AC circuit (Steve and CO feel free to jump in).

 

Here's a link to the basic test procedure for all of the Unilite modules (they're all basically the same).  You'll measure voltage with the coil circuit open and closed, separately.  It will probably be fine.

 

http://static.summitracing.com/global/images/instructions/MAA-unilitedistributorwiringdiagramtestproced.pdf

 

http://www.summitracing.com/parts/maa-4763901/overview/year/1972/make/nissan/model/240z

 

If you've been running rich for 1000 miles your plugs are probably fouled badly and you really just need a tuneup, or at least the plugs need a good cleaning.

[Zed Head]

Forgot to say - welcome to the forum.  The four barrel conversions seem popular over there.  How long have you had the car?  You didn't give any details either, not even year!

[monsween]

Doh! I jumped straight into technical and forgot the basics!

It's a 1971 240z.

Even after cleaning the plugs up they're black again after 10mins so I've got a tuning kit for the carb which I'll fit later tonight and lean it out and see if that helps as well.

I seem to have read a lot about ballast resistor vs no ballast resister, the petronix coil instructions suggest removing it.

[Captain Obvious]

How were you measuring that 6V on the coil? Where were the meter leads and was the engine running at the time?

 

But in the meantime... your issues could be either fuel or spark. If your plugs are black after ten minutes of running, I'd fix that first. There may not be anything wrong with your ignition.