Hello yall,
I have a 1971 nova with a built up 383 and i've recently started to have problems with what i beleive to be my ignition. as i am driving my vehicle my engine cuts off but dosent turn off it will come back on very quickly. i look at my tach and i can see it nose dive then go back up in a hurry it does this intermitenly. but last sunday as i was about to leave the gas station my car would not start at all. it would crank over but not start. when i tried starting it it sounded like it wanted to come to life but wouldn't. http://www.msdignition.com/forum/images/smilies/blushing.gif it kinda sounded like the timing was off or somethin? but would not start. then after i towed it home i tried starting it and it fired right up. i took it for a test run and it kept doin the same thing as before it would cut off but not turn off. please any info would be very helpful because i dont even know where to start thanxx.
http://www.msdignition.com/forum/images/buttons/quote.gif (http://www.msdignition.com/forum/newreply.php?do=newreply&p=50246)

If you do not use the proper coil specified by MSD for their particular ignition box it will cook the coil (cause it to get so hot it will stop working as the circuit opens up like a circuit breaker and will not work again until it cools off). Each coil is impedance matched to each capacitive discharge box. Racers often buy the biggest coil they can get their hands on envisioning a hotter spark. This is a fallacy as the voltage is determined by the resistance of the secondary circuit (spark gap), and the amperage is determined by the flux density in the coil (longer saturation times equals a hotter spark).

Big Dave

If you do not use the proper coil specified by MSD for their particular ignition box it will cook the coil (cause it to get so hot it will stop working as the circuit opens up like a circuit breaker and will not work again until it cools off). Each coil is impedance matched to each capacitive discharge box. Racers often buy the biggest coil they can get their hands on envisioning a hotter spark. This is a fallacy as the voltage is determined by the resistance of the secondary circuit (spark gap), and the amperage is determined by the flux density in the coil (longer saturation times equals a hotter spark).

Big Dave
uh...dave......could we have that in english..........?!?!:eek:








j/k:D
leftcoast carl

Distributor Cap and Rotor: It is recommended to install a new distributor cap and rotor
when installing the MSD Ignition Control. The cap should be clean inside and out especially
the terminals and rotor tip. On vehicles with smaller caps, it is possible for the air inside the
cap to become electrically charged causing crossfire which can result in misfire. This can
be prevented by drilling a couple vent holes in the cap. The holes should be placed between
the terminals, at rotor height and face away from the intake. If your environment demands
it, place a small piece of screen over the hole to act as a filter.

OR......

If your engine continues to run even when the ignition is turned Off you are experiencing
engine Run-On. This usually only occurs on older vehicles with an external voltage regulator.
Because the MSD receives power directly from the battery, it does not require much current
to keep the unit energized. If you are experiencing run-on, it is due to a small amount of
voltage going through the charging lamp indicator and feeding the small Red wire even if
the key is turned off.
Early Ford and GM: To solve the Run-On problem, a Diode is supplied with the MSD in the
parts bag. By installing this Diode in-line of the wire that goes to the Charging indicator, the
voltage is kept from entering the MSD.

Hope this helps...

LS-x motors have four ignition coils on top of one valve cover not for looks but to get a spark hot enough to ignite 500 horse power worth of air and gasoline in a high compression engine. By having each coil fire a plug on alternating banks the circuit that powers the plug stays closed for a longer period of time (called the dwell angle) allowing the magnetic flux lines to build up in the coil (which is a different name for a transformer). So in effect a coil is a flux capacitor (Dr Emmitt Brown did not dream up the "Flux Capacitor") engineers have been sizing them for centuries, to be current and voltage modifiers called transformers.

The capacitive discharge (a capacitor stores electricity not unlike a battery) ignition boxes were designed initially by MSD engineers to fire lean burning charges in two cycle motorcycles, and adapted to the mid seventies lean burn automotive market because the HEI didn’t have enough fire power to light off a lean mixture (mostly air and recycled exhaust gasses).

It acts just like the flashing light you see on the side of the road at a construction site. Inside that yellow box beneath the yellow lens is a big six volt battery and a transistorized square wave circuit to act through a coil so that it charges a gas filled tube that acts like a capacitor. It charges the gas, and charges it, and charges, and charges the gas until it reaches a point were the voltage is high enough to jump across the gas filled gap in the tube to complete the circuit (the spark is akin to the spark in a spark plug). Do you see the light yet?

The MSD is a capacitive discharge system it multiplies the charge that the HEI produces making it capable of either one really big spark jump or a bunch of little ones. That added energy heats up the coil in the circuit. If it is not designed to be able to shed the charge built up in the coil it gets very hot and expands which breaks the soldered wire connections inside the transformer (coil). They are specifically sized to reach zero capacitance or to be totally discharged of their magnetic field (back in the days of points we used a capacitor to send a reversed polarity charge through the coil to collapse any additional magnetic fields to get a fresh charge for the next spark).

Big Dave
(proud owner of both a dwell meter, and a Dual Point Four Lobe Mallory distributor with two of the biggest electrolytic caps you have ever seen on a points fired car).

thanxx guys i think it is my coil......it is a stock hei coil i will replace it this weekend.:hurray:

If you think it's your coil you can bring it to Auto-Zone and they will test it for free .If it tests O.K. then you have eliminated one thing that could be wrong.

I am new here, have posted on the other Team sites, Chevelle and Camaro.

From spending a lot of time around a person named Dave Ray, also known as IgnitionMan, and using 18 of his conversions, I picked this up about MSD red Blaster II and III coils. Those coils, the red Blasters, are not made in the United States any more, but in Mexico. They seem to have problems with the insulation layers between the windings inside the coils. When heat becomes too much for the insulation to handle inside the coil, the insulation deteriorates and falls away from the windings, allowing the windings to touch together, causing what Dave calls a "layer short". This layer short causes both the resistance and the load on the coil to change for the worse, and this can, and usually does cause the ignition module, be it MSD or HEI, to fail from the load going way over its ability to perform correctly.

Reports from various sources have shown that the largest cause of MSD ignition box failures is from coils that have layer shorted.

The chrome MSD coils don't seem to have these problems, and are still made in the U.S.A.

One thing Dave is adamant about is NOT mounting the coil, any oil filled coil, on its side. He says the oil inside the coil MUST cover the windings, to cool them, and laying on their sides only exposes a part of the windings and insulation to the air inside the coil, causing the degradation, module failure and and eventual coil failure.

As jim454 above said, Auto Zone stores can load test the coil for you, and that is the only way Dave says to test them, as resistance values are no longer adequate to show a defective coil, or one that is going defective. Those MSD coils are tested just like a stock GM coil.

Hope this helps

Regards,

Milton