Main Fuse ? THe on-off syndrome

[James W.]

Re: Main Fuse ? THe on-off syndrome

Mark,

You might also try testing the ignition coil capacitor. My '64 roadster would do the very same thing you are describing. I installed a new capacitor, problem went away.


Regards,

James West

[Jack H.]

Re: Main Fuse ? THe on-off syndrome

If the ballast resistor is 'fried' (open circuit), you'll get a different set of symptoms that what's been reported. The engine should crank, fire and IMMEDIATELY die when you release the ignition key from Start to Run position.

On capacitors, YES if the radio RF cap on the igniton coil is 'gone' (either damaged internal dielectric and leaking like a sieve or dead short), you'll rob the ignition coil of it's primary side current. You don't have to replace the cap to troubleshoot, simply remove it and see if problems go away!

There's another cap that can cause problems too. That's the one inside the distributor. It's there to make the spark wave form persist or 'dwell' since when the points open the cap in the distributor plays 'catch' with the coil's primary side inductive windings creating spark output until the points close again. If that cap is a 'goner' you'll get a micosecond spark followed by NOTHING for the balance of the dwell cycle--insufficient power to reliably ignite the cylinder...

Next, eyeball the integrity of the insulation on wire that runs from the ballast resistor to the coil. If it's been damaged by rubbing against 'something', your ignition power could be going to ground BEFORE it gets to the coil...

Next, have you physically checked your points? While rare, they CAN fail with one of the contacts going 'bye bye' leaving you without a spark switching mechanism...

[Mark H.]

Re: Main Fuse ? THe on-off syndrome

James,

Where is that coil capacitor ? I am guessing that it is the 1" cylindrical part that is parallel to the oil, about 2 inches the right (passenger side) ? If so, that could be it. A mechanic down the street told me that it was there only to reduce radio interference and nothing to do with the ignition output ...

Thank, Mark

[Mark H.]

Re: Main Fuse ? THe on-off syndrome

Great info Jack. If you and James are right about the capacitor (and I'm right about where it is), that could be it since I did notice that wire was GONE from the "part" (cap ?) adjacent to the coil. Again, I stopped considering it after my mechanic told me it had nothing to do with the issue. We'll find out tonight !

Mark

[Jack H.]

Re: Main Fuse ? THe on-off syndrome

"I stopped considering it after my mechanic told me it had nothing to do with the issue."

Technically, he's right PRESUMING the cap is functionally intact. Next time you see him, ask him what effect it would have on the ignition if you ran a straight wire from the coil's '+' terminal to ground... I think he'll recant on the radio RF cap not being a 'possibility' for problem(s)!

[Mark H.]

Re: Main Fuse ? THe on-off syndrome

Thank you sir. I'll bet that is the problem. Again, that 1" diameter "thing" held in the coil brackett is the cap, right ? Available at auto store or do I need to go to ZIP/Paragon/etc ?

Mark

[James W.]

Re: Main Fuse ? THe on-off syndrome

James,

Where is that coil capacitor ? I am guessing that it is the 1" cylindrical part that is parallel to the oil, about 2 inches the right (passenger side) ? If so, that could be it. A mechanic down the street told me that it was there only to reduce radio interference and nothing to do with the ignition output ...

Thank, Mark

Mark,

The coil capacitor is found on the right (passengers) side spark plug wire bracket, right next to the coil. An original style will sit straight up and down with the wire on top. It is held in place on the bracket by small phillips head screw that passes through an integral clip at the base of the capacitor.


Regards,

James West

[Mark H.]

Re: Main Fuse ? THe on-off syndrome

Thanks James. I thought that was it. I'll find one tonight (hopefully) and hook it up.

Mark

[Jack H.]

Re: Main Fuse ? THe on-off syndrome

Look in the factory options section of your copy of the AIM (U69 Radio). You'll see the various RF capacitors depicted there.

For mid-year cars, the ignition coil capacitor was unique to Corvette having an integral 'foot' on the bottom for mounting as James West described. The last I looked serviceable replacements were offered by Long Island Corvette Supply...

[Mark H.]

Re: Main Fuse ? THe on-off syndrome

Thanks James, Jack and others.

The capacitor was it. Car starts fine. I bought a cap from a NAPA dealer and it does not have the "foot" it should for mounting. Instead, it has a clamp that mounts it horizontally with the top (end with wire) pointing towards the firewall. Not Top Flight but hopefully OK. Will order another from Rhoad Island next time I order there.

Thanks for all the help !


Mark

[James W.]

Re: Main Fuse ? THe on-off syndrome

Mark,

Great to hear you found the problem, glad I/we could help!


Regards,

James West