'66 427 puzzler - car dies intermittently

[Dan P.]

Hoping to get some input RE a puzzling problem.

Car specs:
L36 AC Coupe
57k original miles
Standard ignition
Bone stock... runs like a sewing machine (when it's running!)

The car has run flawlessly for the 12 years I've owned it. Until yesterday; I drove 35 miles from Seattle to Everett WA with no problem. On my return, about 30 miles into the trip back home, the engine cut out. Died. Kaput. It was like the ignition was turned off - no spark. I coasted across 2 lanes to the side of the freeway. All the other electricals worked fine (radio, lights, signals, etc). I let it sit for 5 min, then it started back up. I idled/revved it for a couple minutes, then as I was about to go, it cut out again.  I had a buddy look at the carb - and it was squirting fuel - so it's not a fuel delivery issue. I made sure the coil wasn't grounding on the ignition shielding - nope. Over a30 min. period It'd start, then die again.

At that point, I called Hagerty and had the car flat-bedded home. When I got there, I rolled off the truck, started it and drove into the garage onto the 4-post lift. Today hoisted it up and checked-out the following:

Ignition shielding grounding coil wire - nope.
Fuse block connections - the ignition wire has already been "jumped" to fix what is a problem with AC cars.
Chased other wires around the ignition & starter to make sure I don't have a grounded or frayed wire somewhere - nada (though I'm sure they get hot)
checked the wiring on the back of the ignition switch - all looks good, solid and tight.

It appears to be an intermittent problem, so I'm hesitant to drive the car and be stranded. I feel like I need to replace any/all suspect parts. What could it be?

Coil?
Condensor?
Ballast Resistor?
Ignition switch?

Any clues for troubles hooting are appreciated... Cheers

[Richard M.]

Re: '66 427 puzzler - car dies intermittently

Dan,

Since you didn't test for ignition spark in your troubleshooting, I'd say check that next. I suspect you have a coil problem which breaks down when hot. Waiting 30 minutes and restarting lets it cool a little but fail temperature may be right at the edge to fail again quickly.

It could be ballast, condenser, or ign switch but when it fails you need to test voltages there right away. My gut tell me it's the coil though......classic way they fail.

Another thought would be the main feed into the fuse panel via the forward harness bulkhead connector at the firewall in the engine bay but because you said you had other power like radio, etc unless it's intermittent problem you couldn't catch at the right moment, I'd say not.

To be certain you need to get to the fail condition again, instead of replacing everything and hope for the best. I'd run in the driveway until normal operating temp and try to make it fail so you can diagnose with the testers, etc. Leave the shielding on to ensure the coil is under the same conditions. The L36 coil is under it, right? You could add some heat with a heat gun to exacerbate the failure, but run the risk of damage so use caution.

Rich
p.s. I learned to carry a spare coil, points, condenser, voltage regulator and a few spark plugs. I even carry a few valve rocker arms since the time one cracked on me years ago far from home. Of course the next time I break down it won't be any of the above......it'll be something I DON'T carry.

[Duke W.]

Re: '66 427 puzzler - car dies intermittently

The bulkhead connector and breaker plate ground wire are the two prime suspects IMO. It could also be a shorted condenser. Rig up a voltmeter in the car with jumpers to the coil + wire and any good ground and drive the car. When it quits if you see no voltage on the meter the problem is upstream - maybe the bulkhead connector or ignition switch. If there is still voltage showing the problem is downstream like the coil, breaker plate ground wire, or shorted condenser.

You can also buy a generic 12V coil for about 20 bucks and swap it in as a test, and it's a good idea to carry a spare coil, point set, and condenser. Use a proven point set and condenser as spares. Prior to removing the point set, adjust the dwell to 30 degrees and verify that the intial timing is in the ballpark. If you have to install the spare point set, the dwell and, therefore, the timing should be nearly right on.

Intermittent electrical problems are very difficult to troubleshoot, but you're better off running a logical test plan with the hope of finding the specific problem before you start throwing parts at it. It will give you more confidence in the long run it you can verify the actual problem.

Duke

[William C.]

Re: '66 427 puzzler - car dies intermittently

I'm with Duke, there is a 2 ga red wire in the pass-thru at the bulkhead. It originally was made of Berylium copper and silver plated to support the full current load of the car and accessories. Over 45-50 years, these tend to become less effective when exposed to multiple (design) lifetimes of use...

[Duke W.]

Re: '66 427 puzzler - car dies intermittently

Here are a couple of tests that may point to or eliminate the bulkhead connector.

1. When it quits, leave the ignition in the ON position. Test for radio and heater blower function. If they don't work that points to the bulkhead connector, or possibly the ignition switch.

2. Move the ignition switch to the ACC position and test the radio and heater blower again. If they work, it could be the ignition switch. If not, the bulkhead connector is the prime suspect.

There have been a number of cases over the year with the same symptoms where the bulkhead connector was the culprit. Sometimes just wiggling it and the harness will get you home. Then you can remove the connectors and inspect/clean all the pins and receptacles. Be carefull removing them. They can be tough to separate, and the plastic gets brittle with age, so they can easily break. Take it slow and easy.

Duke

[Richard M.]

Re: '66 427 puzzler - car dies intermittently

I'd agree that the 12G Red coming through the bulkhead is a common problem for total loss of power, however, in his original post he said his radio worked when the car died. This tells me the ignition switch had power. My gut tells me it's the coil in this case.

Not reading the entire detail, that Red feed in the bulkhead connector was the first thing I thought of when I first read his post because it happened to me in my '63 coupe soon after I got it. I was traveling Route 1 down here in Florida in a one lane construction area, being followed by a Indian River County Sheriff. The car died. He pulled in behind me, got out, checked the car over and liked it. We did some small talk while I opened the hood, looked around, and grabbed the bulkhead connector. I gave it a look, stuck it back onto the firewall connector, and gave it a little wiggle. Got in the car, turned the key to crank and it started right up. He looked in amazement that I fixed it. I drove off and looked in the rear view mirror as he was talking to others that were stopped behind him. I wondered what they were talking about.

Rich

[Dan P.]

Re: '66 427 puzzler - car dies intermittently

Thanks for the insights. It's definitely not the bulkhead connector. It's already been hardwired with a jumper by a previous owner - and for good reason; like most AC cars, the terminal for the wire is pretty fried. All other connections look good though. Radio & lights un-effected when cut-out happens.

The coil, beaker plate ground and the condenser are the next to check. Not putting bets on the coil b/c there's no break-up at higher RPM. It's acting like it's either getting spark or not, so it seems like a short that may be affected by heat. Even then, it seams more like heat soak than reaching a certain temp since it ran for a long distance at the same temp before it cut out - then it kept doing it even after it cooled a bit.

I started the car again today and drove about 5 miles with no problem - but I'm certain it'll happen again. Murphy likes to ride shotgun w/me...

[Michael F.]

Re: '66 427 puzzler - car dies intermittently

I have had that happen twice on a pontiac in late 60s and one of my 67 vettes in the 80s, turned out both times the breaker plate ground wire had a rubbed spot and was grounding out.

[Timothy B.]

Re: '66 427 puzzler - car dies intermittently

Thanks for the insights. It's definitely not the bulkhead connector. It's already been hardwired with a jumper by a previous owner - and for good reason; like most AC cars, the terminal for the wire is pretty fried. All other connections look good though. Radio & lights un-effected when cut-out happens.

The coil, beaker plate ground and the condenser are the next to check. Not putting bets on the coil b/c there's no break-up at higher RPM. It's acting like it's either getting spark or not, so it seems like a short that may be affected by heat. Even then, it seams more like heat soak than reaching a certain temp since it ran for a long distance at the same temp before it cut out - then it kept doing it even after it cooled a bit.

I started the car again today and drove about 5 miles with no problem - but I'm certain it'll happen again. Murphy likes to ride shotgun w/me...

Dan,

IMO, you want Murphy to ride shotgun with you, let it fail so you will be comfortable driving the car.

Take a test light with you and when it fails leave the key in the run position and test for power at the coil + terminal. You will have direction which way to proceed after that. The distributor simply closes a switch, (points) and grounds to provide a circuit for the coil primary but if there is no power at the coil + you direction will be going to the resistor/ignition switch or wiring.

[Dan P.]

Re: '66 427 puzzler - car dies intermittently

Thanks for the tips - makes perfect sense. With you guys around, Amazon doesn't need to sell the book, Troubleshooting Corvette Ignition Problems for Dummies...

Greatly appreciate the advice!

dp

[Jim T.]

Re: '66 427 puzzler - car dies intermittently

Had to walk home from driving my 68 Corvette once. Went back to the 68 with some tools, but it started and drove home. Discovered the problem was the coil. The positive terminal actually turned in the coil. This occurred in 1977 and was the original coil that was installed in the 68.

[Dennis O.]

Re: '66 427 puzzler - car dies intermittently

I have had that happen twice on a pontiac in late 60s and one of my 67 vettes in the 80s, turned out both times the breaker plate ground wire had a rubbed spot and was grounding out.

I had this happen to me in an O/T MG Magnette way back when. It was very hard to find.