Need some guidance out there from my C3 Vette friends.

Have a '68 Big-Block-- all original with <60K miles. Car running great up until a few weeks ago. Took it out to get a small mixture of leaded racing fuel to top off the tank and on the drive home starting getting that "pinging" noise like occurs when you run non-leaded fuel.

Got home---checked timing-- sure enough it was advanced way high.

Long story short, found the problem to be the tip of the rotor button apparently had made contact with the distributor cap itself and actually moved the tip that sends the spark to the distributor towers over approx. 1/4". Thought I'd pull # 1 plug to see how things looked since plugs have been in there for 15+ years (car not driven much) and as luck would have it, pull the tip off the old plug wire.

Purchased new everything--- Delco Remy OEM GM parts including cap, points (D112P with stronger spring), rotor button, condenser, new GM coil, new AC-Delco plugs, and even went ahead and purchased new plug wires (MSD 8.5mm Super Conductor --(saving my two new sets of original GM OEM braided/ wrapped wires for another day) while I was at it. Replaced everything this past weekend.

Went to start car--- turns great, but no spark. Thinking I had a bad coil or condenser perhaps, I replaced both one at a time with another new one and also the original one that I took out. No luck with either the coil or the condenser.

Vacuum advance springs and weights are working fine--- clean and all working without any binding, etc.

Points gapped at .019 (per specs for new points) ---all wires hooked up properly including plug wires in proper ports on distributor cap. Plugs gapped at .035

Out of options--- what else is there that could be causing "no ignition spark?" Car turns over fine.

Any help as to what to check would be greatly appreciated.

 

Is the rotor spinning? The original timing issue could be timing gear. Its about the right mileage to be expecting it.

 

Rotor turning fine--- very little play in shaft.

 

Do you have voltage at the coil when the key is in the 'run' position? Also do you have voltage to the coil when the key is in the 'start' position. You may have missed the second wire coming up from the starter that gives a full 12 volts to the coil during cranking.
When I'm troubleshooting an ignition issue I'll just stay under the hood with a remote trigger for the starter, and run a 12v jumper to the coil so that I can bypass any other wiring issues and focus on getting the engine running.

Good luck

Shawn

 

check volts at the coil, you will see voltage with the points closed and zero voltage with the point open.. if not then your points are grounded or perhaps you have then installed incorrectly...

 

quote "check volts at the coil, you will see voltage with the points closed and zero voltage with the point open.. if not then your points are grounded or perhaps you have then installed incorrectly..."

To clarify, the points only provide a ground to energize the coil. If everything is working correctly you will have voltage to the positive side of the coil regardless of the position of the points.

But with that same thought, I will sometimes unhook the negative coil wire (from the dist) and put a test light in between and turn the engine over. The light should go on and off as the points make and break the ground connection. Just another sanity check when running through the system.

 

I am suspicious. If the rotor somehow hits a terminal inside the cap it will break the rotor or cap- or both- and not just shift itself.

Even if it shifted, that won't change the timing.

If you've found you timing to have changed substantially, either your distributor has slipped in it's mount or you've jumped a tooth on your cam gear.

 

Ive seen em break the tabs that hold the rotor tip in place and turn 45 degrees and still run...Kinda like High Arcing.. The rivet was still holding the tip on the rotor button.. Saw an isuzu run onetime three teeth off on the chain..

 

Do you have the K66 (transistorized) ignition? If so, your pickup coil inside the distributor could be smoked. Similar thing happened to me. Dave Fiedler of TI Specialties rebuilt my dist. and no more problems. Check his website for troubleshooting hints.

 

Points were in fact grounded as you suggested--- thanks for the help. Replaced with another new set of points, buttoned everything back up--- purrs like a kitten now.

My question-- how in the world do the points get "grounded?" I've installed dozens of points over the years and never had this happen. I replaced this coil at the same time--was it something I did unknowingly perhaps, or just a bad set of points?

Thanks again!

 

Points just die. Not all that uncommon. Another thing I've seen (and done!) is setting the points with a feeler gauge. WHile this does work, if there is a trace of oil on the blade of the feeler gauge, it insulates the points. And no way to clean them.