beekppr

In the first day back at this forum, you folks have provided me with a wealth of great information about a couple things on my 64 vert!

Might as well see if someone can help me with this issue. I was helping my buddy get his new 65 GTO dialed in when I noticed that it was running very poorly. I checked the voltage feeding the coil and found it was about 8 volts (cranking) and 7.5 volts in the on position. I'm awful with electrical stuff but I've always understood it should be at 12 volts. I ran a jumper wire straight from the battery to the coil (13 volts) and immediately the engine ran WAY better. Oddly enough, it ran fantastic weeks earlier.

Could this problem be caused by a bad voltage regulator? His car is unrestored but all of the wiring looks absolutely unmolested and original inside and under the hood. Any other thoughts?

LB66383

If the battery is at 13v., my assumption would be that the charging system (alternator, voltage regulator) are working fine. Unless you were using a battery in another vehicle, that is. Anyway, to verify, put your voltmeter across the battery with the engine running. It should be over 13 to about 14v. when you rev the engine a bit.

I assume the GTO, like most other ignition systems of that era, has a ballast resistor. Check the voltage being input to the resistor -- it should be battery voltage or close to it. That should be coming from the ignition switch. Again, like cars of that era, it most likely has harness connectors at the firewall that could have developed high resistance/corrosion over time.

Having said all that, the first thing I would do is throw a new coil at it to see if that makes a difference. An internal short could be pulling down the voltage.

Vitaminmopar

If you measured 12 plus volts at the battery and less than battery voltage at the coil when cranking it is either a wiring problem or a weak battery laying down during cranking. If you have less than 13 volts at the battery with the car running any component of the charging system would be suspect.

You did not say if the car was equipped with transistor ignition. To amend what LB66383 (another Chrysler moniker in the fold) stated. If you have a points ignition, check for burned points or defective capacitor. The purpose of the ballast resister is to limit the current flowing through the points. This helps prolong the life of the points and coil. When cranking the ignition switch routes full battery voltage to the points so a voltage reading should be close to battery voltage on the point side of the ballast, with the ignition switch in the run position the ballast resistor is routed back into the circuit and the voltage should drop roughly in half on the point side. If the points are burned take some 400 sand paper or finer and burnish them, check the capacitor (aka condenser) is not shorted by running temporarily without it. If the capacitor is open the points will pit or burn some and the engine will run poorly, eventually the points will stick together. You can check for open on the capacitor with a multi-meter, easier with an analog than a digital but doable with digital. Set meter to high ohm scale, one meter lead to case, other meter lead to disconnected capacitor wire. The meter should go quickly from zero to infinity, reverse the meter leads at the capacitor and the meter should again go from zero to infinity. This capacitor test is not 100% definitive but should raise the confidence level that the problem is somewhere else. Disconnect your coil and check that the ohmage of your coil is within specification. If the ohmage has increased this will drop current and voltage to the ballast. If you knew all this please don't take away my keyboard. It's late, hope I got that right, I'm off to bed. Hope this was of help.

63split63

Someone may correct me but I think the GTO , like most Chevy's of that era had a resistance wire and not a " resistor " like a Corvette . The wire from the ignition switch to the coil was a resistance wire that reduced the ignition run voltage .
The other wire on the pos side of the coil came from the starter solenoid . It provided battery voltage to the ignition while the starter was cranking .

Bill

beekppr

Thanks for the replies. I am really a moron when it comes to electrical stuff so it takes a bit for the information to really sink in. Helps when you speak slowly and use smaller words.

I should have mentioned that we swapped out the points for an internally mounted conversion kit. The instructions indicated the black wire routes to the negative side of the coil and the red wire to the positive side of the coil. I find no ballast resistor in the engine compartment if that's what you're referring to when you say resistor. I will reread the instructions and see if I overlooked something in the conversion process. As I recall, the instructions had one wire routing hookup for units not having a ballast resistor and a different hookup for those with. I saw no ballast resistor so I chose that option. If there is a "resistor wire" in the system, maybe I created this problem by not getting the conversion installed correctly.

The wiring looks clean and original. Basically, the original wire from the positive side of the coil goes into a wrapped loom so it's hard to trace without cutting the wrap off. The loom traces back to the voltage regulator, the started, the alternator, and the firewall.

I also failed to mention that the battery is new and consistently has 13 volts. It cranks well. When I checked the voltage in the run position, it was before cranking. Next time it's running, I'll check voltage at the battery to ensure it's being charged properly.

He's only had the car a few weeks. It ran very poorly when he got it and all three carbs leaked. We rebuilt the tri power, put in new plugs, wires, cap, rotor, and points conversion. After dialing in the distributor and carbs, it ran phenomenal. The following week it was back to terrible. The jumper wire to the positive side of the coil though really brings it back to live and immediately smoothes it out.

I will also check the coil ohmage. Any idea what it should read? Is there a certain way to test it correctly? It looks to be an original coil from the day. I have others on a shelf somewhere so I'll check mine too for comparison. If his is failing, it would be a simple fix to swap in one of my extras.

I also have an extra voltage regulator. Is the voltage regulator more for ensuring proper charging voltage to the battery or could it play a role in this low coil voltage problem?

Lastly, if I can't find the problem, is there a simple quick fix to restore the right amount of voltage to the coil? Someday, he may restore the car and then he can replace all the wiring and make it more correct. He's not overly concerned about correctness at this point as long as the fix is safe and reliable. There are other matters on the car we want to tackle but we need it running well first.

Thanks everyone for taking the time to talk me through this stuff. I really appreciate it!

jason_marshall1

It might be worth to clean the connections through the firewall plug. If it's original like you say, it's very likely there is corrosion on those tiny, hard to reach, miserable to clean pins. Even if it doesn't solve this issue, it can't hurt. Good luck!

GearheadJoe

Just to reinforce what others have said, a 1965 GM car likely had a ballast resistor (or possibly a resistance wire, but I think that came later).

The factory setup applied full battery voltage to the positive lead of the coil only during cranking, to temporarily deliver a hotter spark for starting the engine.

Once the ignition key reverted to the "run" position, the ballast resistor (or resistance wire) was switched in series between the battery and the positive terminal of the coil. This had the effect of reducing the current/voltage available to the coil to reduce degradation of the points. If you use a simple voltmeter to measure the voltage at the coil with the engine running, you will likely read about 8 volts.

Please tell us what specific points-elimination kit you installed. Some of these kits require that you bypass the ballast resistor. They may also require changing to a coil that is designed to operate without a ballast resistor. Perhaps you can study the installation instructions to see if they mention what to do about the ballast resistor.

beekppr

It's a pertronix kit. I studied them again today and I'm fairly certain I made a mistake. I didn't find a ballast resistor so I assumed it had none. I now believe it has a resistor wire and I'll verify by opening up the loom. Pertronix recommends bypassing it which I will do. They also strongly recommend using one of their coils with internal resistors feeding it with full voltage so we are gonna do that too.

I think Jason's advice is good on cleaning the pins just as insurance if nothing else.

dcamick

Sorry, No input!!!! Great reading! As usual....

Mark Lovejoy

One other often overlooked issue is grounding.

Make sure there is a good ground strap from the engine to the chassis. If the original ground strap has been compromised strange things can happen. A quick test is using a set of jumper cables. Clip one end of the black cable to a good clean spot on the engine and the other end to the negative battery terminal. You might be surprised.

beekppr

Great point...We never bothered to look at that so we will check that too.

Frankie the Fink

Frankly - I'd swap the points back in as a test and when doing so, examine the small wire to the points breaker plate CAREFULLY. They often get frayed and/or loose...

jim lockwood

Frankie, are you ill?

MOXIE62

I've always been confused on which ballast to use of a 63. LIC states the early cars use the ballast with a black dot and cars after Feb 63 use the stripe one. How does the ballast know what year car it is on. Maybe the coils were changed during that time which called for higher ohm's.

GearheadJoe

My understanding is that the original "block dot" '63 ballast resistor had a very low resistance value of about 0.3 ohms IIRC. Customers complained about the points not lasting very long, so GM changed the resistor to the the "blue stripe" version that was about 1.6 ohms. This made things easier on the points.

I do not know if the coil was changed at the same time, but someone here will likely know.

MOXIE62

Yes, I've read the service bulletin which states going to the higher OHM's in Feb. 63 but says nothing about the coil. I'm using a blue stripe resistor, 1.8 OHMs and a Pertronix Flamethrower coil which is 1.5 OHMs. No points failure yet, thanks

Frankie the Fink

A moment of weakness for certain....

Tampa Jerry

GM went to a resistor wire in vettes in 68. The stock resistor wire is easy to spot. It looks like an old toaster wire. It was fabric wrapped strand wire. The longer the wire, the higher the resistance. My 68 has the wire. I bypassed the wire in my 68, which has a Petronix ignition, by running a wire from the starter which is energized when the engine is running to the positive side of the coil. I don't remember what my 65 GTO had for an ignition source. It has been 45 years since I had the car. The Pertonix likes 12 plus volts to run correctly. Keep us posted. Jerry

beekppr

My buddy and I have different work schedules so we are still trying to find time to work on it together. I like your idea of running the bypass wire directly from the starter. Something occurred to me the other day though...wouldn't the resistor only lower voltage to the coil when the key is in the run position? We found low voltage in both the run position and the cranking position.

I'm definitely going to start with cleaning terminals at the firewall plugs and ensuring the grounds are good. I'll check voltage at various terminals and hopefully, I can just put in a bypass wire like you did.

We also decided to run the Pertronix higher voltage coil that the kit recommends. It advises to feed it with full voltage at all times and it has its own internal resistors.

I'll post what we found/did soon.

Thanks for all the input!

domenic tallarita

For what it's worth, there will be low voltage while cranking because of the draw the starter has on the battery. That's the reason they bypass the resistor and go directly to the coil + from the solonoid.
We used to put a jumper across the resistor when we drag raced. It does give more spark, but at the cost of the points.

Dom