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

[Asa Jay Laughton]

Kirk,

Great explanation!  It took me a couple of reads, but I got the 
schematic mapped in my head.  I think it was a very clever way to do 
it.  Nice work.  I may have to consider this in other projects I have.

So do you think the coil burn-out was due to removing the resistor, or 
do you think it would have burned out anyway?

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:
> 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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