[DeTomaso] Dura-spark key-on coil burn-up fix

Kirk Evans kre at adelphia.net
Wed Jun 27 20:27:38 EDT 2007


Asa,

What happened to me was this---I installed a Duraspark box---wired it 
accordingly---started the car and it had no power. I started looking a every 
item that could drop power---testing---changing---checking---re-checking---  
with no results. During one of the tests, I pulled the resister on the coil 
as  directed by the MSD tec guy and 5 to 10 minutes later the coil was 
scrap. Put in a new coil and still no power. Then, being totally frustrated, 
I, just out of the clear blue, decided to put on an external ground on the 
Duraspark box. One alligator ground clip later full engine power was 
achieved. No where in any Duraspark diagrams showed the box needing a 
chassis ground but in the past, I have always mounted the box direct. This 
time to help vibration and backside cooling, I used a MSD rubber mount stud 
kit that totally insulated the box.

Regardless my fix to prevent a "key on" burn out was this. I put in a relay 
with the incoming ignition power feed to the incoming feed on the relay. The 
outgoing feed went to the coil and Duraspark box and was also cross 
connected to one of the control coil blades on the relay. This will keep the 
relay on when it's energized. Along with the back-feed wire on the control 
coil, I fed the same terminal with the starter solenoid feed wire from the 
ignition. I put on a diode to prevent the starter for being fed by the relay 
keeping the solenoid engaged after the key is released. Last the other side 
of the relay control coil was grounded. Now when the key is on, no power 
goes to the box or coil. Once the started is tripped, the relay energizes 
and feeds the ignition accordingly---now the car is running---and the relay 
feeds it's control coil from the outgoing terminal. Downside---If the car 
stalls, the relay stays engaged until the key is shut off. Once the key is 
shut off, the relay dis-engaged no longer powering the coil and Duraspark 
until you again trip the key---energizing the ignition parts when needed.

This is not a perfect fix but if your working on your car or in the case of 
Larry Stock who often has left his key on when loading or un-loading his car 
(needing to turn it with the windows down) from a trailer, it will prevent 
the burnout problem. There it is---FWIW. The explanation is wordy---let me 
know if you need a print. Thanks Asa.

Kirk

----- Original Message ----- 
From: "Asa Jay Laughton" <asajay at asajay.com>
To: "Kirk Evans" <kre at adelphia.net>
Cc: <detomaso at realbig.com>
Sent: Thursday, June 21, 2007 12:28 AM
Subject: Re: [DeTomaso] Dura-spark key-on coil burn-up fix


> Well since nobody else replied, I will. :)
>
> I've been running a Duraspark II system in the Mach I for nearly 20 years, 
> with a stock coil.  No problems really.  So my first question is, was this 
> due to the coil being an MSD?  If so, why?   Seems to me I've left the key 
> on for longer than five minutes before with no ill affects.  I know 
> leaving the key on can overheat the coil, yes, but what was so sensitive 
> in the MSD that cooked it?
>
> And yes, I'd be interested in your fix. ;)
>
> Asa Jay
>
> Asa Jay Laughton, MSgt, USAFR, Retired
>
> & Shelley Marie
> Spokane, WA
>
> 1973 Pantera L 5533
> [ASASCAT]
>    ******************************     http://www.asajay.com
> http://www.351c.info
>
>
>
> Kirk Evans wrote:
>> Hi all,
>>
>> I torched a new MSD coil last week with a Dura Spark box---key left on 
>> for 5 minutes---first time ever---my bad. BUT because it happened, I came 
>> up with a simple relay fix for those who are interested. Hope it will 
>> help a few more Dura Spark users.
>>
>> Kirk _______________________________________________
>>
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> 





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