Lost spark [ Best ignition coil for a stock '79]

Lost spark [ Best ignition coil for a stock '79]

Long story short, it's time to change my ignition coil on my all stock '79. I'd rather not put a "stock" coil back on it and would like to put the hottest thing on it that's compatable w/ the stock dizzy & etc.

Anything alvalible for ballasted 1500's other than stock?

Can I run the Lucas sport coil w/o a resisitor or will that fry the dizzy?

Would I have to change trigger mechanism in order to run A "HOTTER" coil? ( Pertronix maybe?)

Thanks, BIlly

Re: Best ignition coil for a stock '79

Not sure what the stock ignition is capable of driving, but you might want to consider a Pertronix. The stock electronic ignition was notorious for frequent failures. Lucas finally ditched the old system and was retrofitting the failed ones with a completely different one. Pertronix makes a replacement that's easy to install. FYI, the ballast resistor is NOT the resistor attached to the pedal box, it's actually a resistance wire built into the harness.

Out of curiosity, what's wrong with the stock coil?

Re: Best ignition coil for a stock '79

Arching from the coil tower to the + - leads on the sides. Good plugs, cap, rotor and wire. Can only see it at night. The car runs fine and once it warms sometimes it misses under load. It acts like a carb, but it's brand new (DGV). I pulled it down anyway just to chaeck and all seems fine. A little casting flash that came right out. I thought that might be it but now it's doing it again.

I might swap to pertronix and a hotter coil. Thanks for the heads up on the ressitor as I would have bet $$$ it was the one on the pedal box.

Re: Best ignition coil for a stock '79

sparkydave said:

FYI, the ballast resistor is NOT the resistor attached to the pedal box, it's actually a resistance wire built into the harness.

Click to expand...

Splain Lucy Slain.... Seriously, can someone elaborate more on this.

Re: Best ignition coil for a stock '79

tweety said:

sparkydave said:

FYI, the ballast resistor is NOT the resistor attached to the pedal box, it's actually a resistance wire built into the harness.

Click to expand...

Splain Lucy Slain.... Seriously, can someone elaborate more on this.

Click to expand...

The resistor attached to the pedal box is called the drive resistor, and it's actually part of the stock electronic ignition system, but it's not the ballast resistor in the coil's primary. An aftermarket ignition system like the Pertronix won't need that drive resistor. I left mine in place, and left it connected to the distributor's wiring harness so that I could drop in a still-working stock distributor. The ballast resistor for the coil isn't a discrete resistor (i.e., you won't find an actual resistor anywhere), but it's a resistive wire that looks like ordinary wire.

Re: Best ignition coil for a stock '79

ok, that all makes sense......

Is the entire resistive wire white/green? Is the entire lenght of the wire used to achieve the resistance, or is it a short length? What happens if that wires fails? Can it be replaced with a standard coil resistor? If you go with a non ballasted coil, can you just bypass it?

For some reason, this post made all of this "click" in my head. The main reason I ask about the wore failing is that I found a "burned" wire in the engine bay harness. I found it shortly after I bought the car. I did not burn via any type of contact with a hot item, it burned from the inside out. The burned area was short (only about 4") so I simply spliced a new piece of wire in its place. Off the top of my head, I can't remember what color the wire was. I do recall it was connected to the starter solenoid.

This all just has me wondering if this wire might have been the resistive wire. Resistors do their thing by throwing off voltage via heat. Too much heat means that the resistive wire would cook.

Sometimes I think too much, but that's how I learn.

Re: Best ignition coil for a stock '79

.......anyway, the car crapped out on me today. It started running on 3 cyls. I pulled over to check it and had no spark to #1. I turned around to go back home and lot all spark.

I check all of my manuals and there are NO specs at all for ANY of the ignition componants. I've done some preliminary testing and have 3.4 ohms across the pickup and voltage to the coil.

What's the specs on the box?

Also, I think my pick up has been changed as the pug on the dizzy side is different from the box. It looks to be aftermarket but I don't know for sure.

I want all of this stock garbage gone. Is petronix stand alone or needs to go through the box?

Re: Best ignition coil for a stock '79

The traditional color Lucas used for the ballast/resistor wire is "Pink" or Pink/white. It's unlikely to burn out unless you shorted its far end (away from the ignition switch) to ground. However, anything is possible with Lucas.

Sorry, I don't have any suggestions about alternate performance coils.

Re: Best ignition coil for a stock '79

I just realized, I have 12v to a coil that reads 1.8 ohms. That isn't right! No wonder it went "POOF". The strange thing is, I've never had any problem with it and had driven it off-and-on for 6 years and 6000 miles just like it is. I didn't touch ANYTHING on the ignition.

No pink wire, I've got double white wires w/ green stripes. I have a signal from the pickup. It's had to read but it's there. My meter isn't quick enough to get a ggod reading. If I knew which end was up on the pickup coil, I'd just convert to GM 4 prong HEI module. I really think it's the box.

Re: Best ignition coil for a stock '79

Before you say you have a problem based on your voltage measurement... read on.

You cannot simply turn the ignition switch and make a voltage measurement from coil (+) to earth to determine the coil voltage. You MUST make sure current is flowing through the coil when you make this measurement. This is easily done by one of two ways.
1) on cars with points, remove the dizzy cap and fit a coin between the contacts, then make your voltage measurement.
2) on cars with electronic ignition (or on cars with points if you prefer this method) run a jumper wire temporarily from coil (-) to ground.

With either of these methods, you are assuring that the coil power has a path to ground and therefore, any voltage drop created by the ballast resistor or resistor wire is will be measurable between coil (+) and ground. If you fail to use one of these two methods, there's a chance the points are open (or ignition module is "off") and therefore no current flow. When current is NOT flowing you will ALWAYS measure battery voltage on coil (+) when the ignition is on.

Succinctly, you must have current flowing through the circuit for the ballast resistor to create the voltage drop at the coil.

Re: Best ignition coil for a stock '79

Doug, what you're saying doesn't make any sense as the resistor in my case is (supposed) to be b/w the coil and battery, thus voltage will be dropped to the coil when the wire is grounded....either through the module or a voltmeter, it doesn't matter as the wire is still seeing ground either way and current is flowing through the wire to the mater and then ground.

Moss Motors ever says to perform the same test to see if your car is equipted with a ballast resistor or not. I'll get the link in a minute.

Here it is:

https://www.youtube.com/watch?v=pWxJmbm5V3s&feature=player_embedded

Don't forget, I'm concerned about voltage TO the coil, not THROUGH it as I already know my coil resistance vaule so voltage drop is not needed.

Re: Best ignition coil for a stock '79

The Lucas electronic ignitions are not something I work with so I cannot comment on their specifics. Regardless, I have watched the YouTube video link you provided and frankly, they are wrong and have oversimplified the test.

I wrote and deleted a lengthy explanation. Suffice it to say that the Moss video demonstrates half the test steps. They are assuming that the points are closed (or module conducting) to determine the coil operating voltage. The points must be closed so current will flow which allows the ballast resistor to "drop" the coil voltage. You cannot assume that the points are closed. The added steps I listed above (coin between the points or a jumper wire to ground from coil (-)) will insure current is flowing through the coil (and any ballast resistor) during the measurements. Skip that step and your readings WILL give you a 12V reading if the points (or module) are open.

Also, a voltmeter is not a path to ground, exactly the opposite. Multimeters are set up to have very, very high impedance so they do not become a conductive part of the circuit. You do not want a volt meter providing a "short" to ground during test measurements.

Re: Best ignition coil for a stock '79

In the intrest of science (and the fact I like to argue and be right) I rigged up a test using a light to replace the grounded coil to simulate current flow as you described. The results prove undoubtedly that you sir are.......................CORRECT !!!!!!!

It dropped down to 8.5 ahead of the light.

What I don't understand is why are they running a resisted wire to a GM module designed to run off of 12V straight......unless the pickup coil can't handle it or this is the "other" system used later to replace it?

Re: Best ignition coil for a stock '79

Again, I'm not familiar with the Lucas electronic ignitions so I can't comment about why they powered the module the way they did. Powering the module from a line with a voltage drop does sound like a problem. However, perhaps they designed the module so it can operate from supplies ranging from 6V to 14V. I simply don't know.

I do know that an often reported problem with Pertronix modules is when their power supply line is connected to coil (+) on ballasted ignition systems. Some Pertronix modules seem to work OK with that reduced voltage, many do not.

Re: Best ignition coil for a stock '79

I can't comment on the Youtube video yet, but I concur that if the points are open then just measuring voltage across the coil won't work. It's possible an electronic ignition can have the same problem if one of the rotor slots lined up with the pickup. Connecting a jumper from the coil "-" to ground and measuring between ground and the coil "+" with the ignition on would be a sure fire way to determine if you have a ballasted system or not; ~12 volts would be no ballast, ~6 volts would be with ballast. Since the jumper would be diverting the current, it would also be safe to do this with a Pertronix without having to worry about overheating the Pertronix module.

Re: Best ignition coil for a stock '79

I've been requested to comment, but as with most things in my life, I'm coming in late.

Doug is quite right, of course, and, as usual, explained it all very well. I'd only add a couple things: first, if you ground the negative terminal of the coil, either with a jumper or by putting a coin in the points, be sure that power is off before you disconnect the jumper or remove the coin. If it's hot, breaking that connection will generate a voltage spike that will definitely get your attention. Second, measuring the voltage at the coil, with the points closed as suggested, will tell you if you have an external ballast resistor, but you may have a 12-volt or, as it is sometimes called, an "internally ballasted" coil. That's just a coil with a higher resistance, so it doesn't need an external ballast resistor. In that case, you'll see 12 volts in the measurement, since you don't have an external resistor. But that doesn't mean that you need one.

One of the best ways to tell if you have a ballast resistor is just to look for the sucker. They're not microscopic. If you don't see one, you might still have a resistor wire that performs the same function or a ballast resistor mounted somewhere out of sight. So, the voltage measurement, properly done, still makes sense.

Re: Best ignition coil for a stock '79

Thank you Steve and Dave. Your comments are greatly appreciated. Good point about shutting off power before removing the jumper or coin. I have been "bitten" by forgetting that.

Re: Best ignition coil for a stock '79

see post below (I couldn't get the quote to stick)

Re: Best ignition coil for a stock '79

kellysguy said:

In the intrest of science (and the fact I like to argue and be right) I rigged up a test using a light to replace the grounded coil to simulate current flow as you described. The results prove undoubtedly that you sir are.......................CORRECT !!!!!!!

It dropped down to 8.5 ahead of the light.

What I don't understand is why are they running a resisted wire to a GM module designed to run off of 12V straight......unless the pickup coil can't handle it or this is the "other" system used later to replace it?

Click to expand...

You must have missed the above post.

It's a stock '79, no points.