65 Points Ignition starting issue

[Peter S.]

I've been struggling with this issue for over a year, and just can't understand what might be happening.

65 327, breaker points ignition.

Most recently, started the car at least 30 times in a row over 3 months without a single problem. It starts immediately and runs perfectly.

But then, and this has happened several times by now over the last 2 years, it won't start for nuthin. It will crank fine but is not getting any spark. I checked with a timing light and there is no light.

I put in a different coil, and that's all I do, and then it starts right up. I have 3 different coils, all good, and it doesn't matter which one I switch to, it starts right up after switching it out!

Today it wouldn't start after I drove 5 blocks and shut it off (hardware store). Put in a different coil, started right up. Drove a few blocks, switched back to the prior coil, started right up!

I've replaced the distributor to coil wire multiple times. The low voltage wires and connections on the coil look fine too.

Hot, cold, warm outside, cold outside, doesn't seem to matter. What could I check?

[Gary J.]

Try replacing the white porcelain resistor block on the firewall.

Gary

[Mark E.]

Try replacing the white porcelain resistor block on the firewall.

Gary

What Gary said.

When it happens, what's the voltage at + terminal of coil?

Should be full battery voltage while cranking, a few volts less with ignition on but not cranking.

If that checks okay, check dwell while cranking.

[Peter S.]

I forgot to mention, I did also replace the points and condenser before I figured out that swapping the coil fixed it.

[David H.]

Peter

Don't think swapping coil is fixing anything as your issue returns.

Below is a wiring diagram for mid-years.

With ignition key to "START" - power directly from solenoid to coil. Once car starts (key to "RUN") power thru ignition lock to ballast resistor and on to coil.

If it STARTED and then didn't run. I'd suspect you had lock to ballast resistor to coil problems.

As sometime it does, and sometimes it doesn't start. And sometimes it starts and runs just fine - I would check out your distributor.

Possible new points/condenser change has damaged that wire from distributor that triggers your coil?

You mess with your coil, and by necessity you mess with that wire. Intermittent short where wire exits distributor my $.02. or Same wire - broken internally making connection sometimes.



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[Mark E.]

I forgot to mention, I did also replace the points and condenser before I figured out that swapping the coil fixed it.

Still suggest performing checks recommended above.

[Duke W.]

There are a couple of tests you can run. You'll need some jumper wires. Given that swapping out coils solves the problem temporarily likely means the coil(s) aren't he problem.

Rig up a voltmeter in the cockpit and monitor voltage at the + coil terminal while driving. If voltage remains even when the engine quits it likely means the coil ground circuit is bad, and this is likely the ground wire from the distributor to the coil negative terminal, but it could also be the points or condenser.

This ground wire is part of the breaker plate assembly, and it is constantly flexed by breaker plate rotation commanded by the VAC, so it eventually work hardens and will break. Back in 2012 I was overhauling a local chapter members '65 L-79 distributor, and when I removed the breaker plate the wire broke. We rigged up a temporary ground wire with some generic wire and terminals, and the owner later bought a NAPA replacement wire that can be installed without disassembling the distributor.

I documented all of the above in a thread I started both here and on the CF, so search both. My CF handle was SWCDuke.

To test the above use a short jumper wire with alligator clips. Attach one end to the breaker plate through the cap window and the other to a good ground. For this test disconnect the VAC signal hose and plug it with a golf tee. This will prevent the breaker plate from moving, so the ground wire remains attached.

You will need to use the idle speed screw to increase idle speed as the loss of idle advance will clause loss of idle speed and the engine will likely run hotter.

If the stalling doesn't occur then the problem is the ground circuit, and if that's the case I suggest you do a "blueprint overhaul" as outlined in the referenced TDB and CF threads.

The procedure is in your 1963 Corvette shop manual, but make sure the dimple in the gear is pointing the same direction as the rotor tip upon disassembly and make sure you install it the same way. This is not mentioned in the shop manual overhaul procedure and has been causing problems ever since.

Also make sure you index the engine at the initial timing point BTDC #1 before you remove the distributor. If you don't understand why search the CF for the last thread started over there, which is a detailed step by step instruction of how to properly remove and install a C2 distributor that few guys understand, and that's why there are many vintage Corvettes out there that operate poorly due to improper distributor assembly (dimple orientation) and/or improper installation.

Duke