1969 427/390

[Salvatore I.]

I recently performed a full tune up on my 427/390. I used a hotter spark plug as recommended here in this NCRS forum, new points, etc...but am experiencing a problem that I didn't have before: The car is having difficulty starting. Running a 12volt tester on the alt, shows a good reading but not so at the coil. I jiggled the red coil lead wire and low and behold, the 12 volt light went bright...

About an inch to so from the end of the lead, I noticed that the wire beneath was thin as though crushed and I then re-spliced the wire and reconnected to the coil...the test light was bright and the car kicked right over...

After a day or two, I went to start the car, and again same starting problem...12 volt is bright at the alt but no reading at the coil....When I leave the ignition key in the "start" position for about 1 minute, the red lead wire at the coil is running hotter, signaling a bad wire/short or whatever...but can there be an open there from a cutoff?

Is there a built in cut off in 1969 427/390's as part of the alarm system installed in the car? I checked the owner's manual and service manuals and can't get any info on this system...It seems as though there is a cutoff somewhere, but I cannot find it....Thoughts on what this could be? Where I should test first or sequence to solve the problem?

The "firewall" wiring appears to be original but the secondary wiring, like at the alt, appears to have been replaced more recently...Suggestions are appreciated....

[Stephen L.]

Re: 1969 427/390

I'll give it a shot at troubleshooting.... Your description is somewhat confusing so I'll try to describe how the system works.

The voltage at the coil (+) is as follows:

Assume everything is properly connected.....

When attempting to start the engine AND the starter solenoid is engaged (starter turning) 12 vdc will be at the coil (+). When you release the key to the run condition, the voltage will drop to about 8vdc at the coil. This is caused by the solenoid applying 12 vdc to the coil...at the same lead that is the secondary side of the ballast resistor. After the engine starts and you release the key, the ballast resistor is in the circuit dropping the voltage to extend the life of the coil. Look at the ballast resistor carefully. One end should have a single pink lead. This is the source of 12vdc from the ignition switch. The other end of the ballast resistor will have a pink lead going to the coil (about 8 vdc). Also at the coil will be a smaller pink lead. This comes from the starter solenoid and supplies 12vdc during "start". With the help of a friend check the voltage at the coil (+) during start. It should be "bright" on your light, dimming when the key is released. If it doesn't glow bright during start you have a wiring (small wire) or solenoid problem.

[Salvatore I.]

Re: 1969 427/390

Steve

Let me clarify, I used a 12 volt test light not a meter and had a bright light at the alt but not at the coil until I jiggled the coil wire and then the 12volt test light went bright, signalling a connection...The car started ok...when the 12 volt test light doesn't light at the coil, I can't get the car to start..there is no spark at the distrbutor or at the plugs when I go to turn her over..The engine shurns but there is NO SPARK.....This means to me that something is cutting off the circuit to the coil or from the coil to the distributor making there be no spark to start the car.....I suspect some kind of cutoff switch or a very bad connection somewhere.....

Where shall I look for the cutoff switch or what is the sequence to follow to find the short?

I am very new to this, so forgive me if I am not clear...

[Jim T.]

Re: 1969 427/390

Sal your 69 did not leave the factory with a ballast resistor. 1967 was the last year for ballast resistors as I know it. Your 69 has 12 volts going from the ignition switch to the fuse block side inside the car. From the fuse block on the firewall your 69 has a resistor wire going to the coil. Initially the resistor wire will give the 12 volts to the coil, but only initially because the resistor wire will reduce the voltage to prevent the points from burning.
I do not know your exact problem, however there are a couple things you can do to keep driving your car. The first one is to replace the resistor wire from the fuse block to the coil. Not uptaping the wiring harness harness a separate wire can be used. You will have to find an old donor car and remove the resistor wire. Any GM point type car without a ballast resistor will work, just remove it from the firewall fuse block, and the wiring harness. The length of the resistor wire is important, do not cut the ends, remove it with the terminals on the wire. Another choice is to install a ballast resistor, run a wire from the firewall fuse block connector for the resistor wire to the ballast and a wire from the ballast to the coil. One other option is to install a Pertronix ignition unit to replace the points, it requires 12 volts so the ballast resistor would not be needed. If you do not want to mess with the fuse block, you can connect a wire to the inside fuse block terminal marked "IGN" and have 12 volts when the key is turned on. Since you had no problem untill the tune-up and you mention jiggling the coil wire you may have the terminal on the coil as the problem. I had one give me trouble once and after a lot of troubleshooting, walking home, I found the problem. The coil terminal was turning in the coil. New coil fixed that problem.

[Salvatore I.]

Re: 1969 427/390

Thanks, Jim...I will try what you suggest....

the wire to the coil is 36++ years old and I guess it could be the sole culprit or the coil itself. The coil is a newer replacement/aftermarket piece....I will tell you that the coil looks ok and I do get it to start at times and then not....But, it could be the problem...

My gut tells me that there is a loose connection somewhere, it it as though whatever it is is "switching on" and then "switching off", (like a toggle) but I can't figure out how to go about the process of finding exactly where the problem is....It could be the coil itself and I will replace it unless there is a way to test it to know it is sound?

I guess then the next step would be to just replace the whole wire going to the fuse block...is that what you are suggesting?

Sorry, I am really not very good yet in understanding all of this, but appreciate the feedback...

[Jim T.]

Re: 1969 427/390

Rereading your initial post you mention a red wire going to the coil. Your 69 should have the a resistor type wire that is covered with a cloth type material. The color is a light tan/beige. The ignition resistor wire to the coil does not have a plastic type protective covering. Someone has done some wiring changes.

[Joe L.]

Re: 1969 427/390

Sal-----

There is NO ignition cut-off feature which is part of the 1969 UA-6 alarm system. The system provides an "audible alarm" only---nothing more.