1971 Transistorized Ignition Problem

[Dan D.]

Re: 1971 Transistorized Ignition Problem

Let me try and help a little on the role of the capacitor in point ignition systems. The capacitor across the points does 2 things. First, it absorbs energy from the coil when the points open, which is essential for point life. When the points open the capacitor will initially absorb the current flowing in the coil until the capacitor is fully charged. This current, which is also at a high voltage, would otherwise cause the points to arc when they open.

The second thing the capacitor does is it absorbs a condition known as 'ringing' in the coil. When the points open and the magnetic field in the coil collapses, the spark is generated. But the coil also produces several transient waveforms that produce spark out of sequence until the magnetic field in the coil is totally collapsed. These unwanted transients will cause misfiring as the cylinders are not ready for this spark.

When the points close again, the capacitor is then grounded and thus totally discharged. It will remain discharged until the points open and the cycle starts over again.

Hope this helps some.

-Dan-

[Paul C.]

Re: 1971 Transistorized Ignition Problem

YEA! TEA! As soon as the capacitor was REMOVED from the positive coil terminal the car ran fine. Thank you to the engineers out there Jack Humphrey and Duke Williams for pointing me in the right direction. There should not be a capacitor on the coil.

Paul

[Paul O.]

Re: 1971 Transistorized Ignition Problem

Hate to say this but all original 71 LT-1 I have seen do have that capacitor. My original 71 had one what you may have is a defective capacitor that is causing the problem.

[Dan D.]

Re: 1971 Transistorized Ignition Problem

That capacitor should not have caused the problem you were experiencing. You probably have a defective capacitor.

-Dan-

[Duke W.]

Re: 1971 Transistorized Ignition Problem

There seem to be questions about whether that cap was used on TI, but it should function the same as on a point ignition.

Chances are it's either shorted or leaky. Check resistance between the terminal and case. It should be infinite, but it still may have microleaks that affect its performance. A typical inexpensive ohmmeter puts a very low voltage across the device, which may not be enough to cause leakage. It takes specialized equipment to fully test a cap.

Duke

[Paul C.]

Re: 1971 Transistorized Ignition Problem

There are TI cars that came from the factory with capacitors--I agree but as another person who emailed stated "Plus, if I remember correctly there was a service bulletin to that effect."

There is no need for a capacitor on a TI car because is doesn't have points. I am just trying to help others--if you ave a TI system problem--first remove the capacitor because if it is bad it will cause misfires.

Again thanks to all those individuals who helped my solve this mystery--it is greatly appreciated.

[Paul O.]

Re: 1971 Transistorized Ignition Problem

Paul

Where in AIM does it state that K-66 equipped cars do not have the capacitor installed? In what section of the AIM is that?

As for the difference between a car with points and a TI system. In the TI there is a magnetic field expanding and collapsing which in-turn could cause radio static. Also a point system car has additional shielding inside and under the distributor cap. The only time I would not expect a capacitor on the coil is a car that did not have the radio option.

[Paul C.]

Re: 1971 Transistorized Ignition Problem

That was a response that was sent to me. My guess is it's page AIM 1971 L362 A7 LS6. Te page shows the TI system and shows no capacitor. The bottom line is some cars have it and some don't. My guess is if the capacitor is OK no problems, if it is bad then misfires. If you have had your car NCRS judged--there is no judging of the presence or absence of a capacitor under Distributor & coil--so the point is moot.

[Paul O.]

Re: 1971 Transistorized Ignition Problem

So if you go to page 411 AIM U69 A4 there is the capacitor install if one has optioned for a radio. It does not differentiate between Base, LT-1, Big Block or LS6 only is a radio is installed.

[Ray K.]

Re: 1971 Transistorized Ignition Problem

My '65 equipped with the K-66 option does not have a capacitor. Never did. A quick search through the '65 AIM did not indicate that they were installed. Does not seem that one would be required but others have documented TI with a capacitor, maybe in later years as is this '71.

Ray

[Paul C.]

Re: 1971 Transistorized Ignition Problem

My 1971 LT-1 didn't have one but I saw it was in the judging manual so I added one--my costly mistake.

[Paul O.]

Re: 1971 Transistorized Ignition Problem

The problem here is you are looking at this as a K-66 issue and it is not. What you have here is a 1971 LT-1 that if it is equipped with a radio. Then this capacitor is installed and it does not mater what engine or ignition system is installed only does it have a radio. Using a 1965 AIM has no collation to this installation.

[Paul C.]

Re: 1971 Transistorized Ignition Problem

I started this thread to figure out way my car was misfiring and I figured that out. I'm not here to debate whether at TI cars had a capacitor on the coil and my mistakje was talking about something outside my area of expertise. I am not a judge and don't claim to be an expert on C2 or C3 TI corvettes--I leave that to others who are much more knowledgeable than myself. I am not the original owner of my 71 and can not speak to how it came from the factory originally. Again thanks to all those who helped me to understand the TI system and solve my problem---it is greatly appreciated and I commend all of you for sharing your knowledge/expertise with me. As Porky Pig said "Th-th-th-That's all folks".