1967 won't run after 30 minutes

[Lee B.]

Re: 1967 won't run after 30 minutes

I took the alternator over to the shop to get rebuilt last week and when he tested it, he said he could not do anything to it because nothing was wrong with it. I took it over to him again today and he said he could not rebuild what wasn't broke. However, I asked him to test it before I left and this time, it was broken. It did not do anything. So he said the good news is that he can fix it now that something is broke. Should have it back Friday. Try that fix.

[Lee B.]

Re: 1967 won't run after 30 minutes

So I got the alternator back and I think the main problem is solved. Apparently when the repair guy opened up the case, the ground screw for the brushes was backed almost all the way out. He said that this would cause the alternator to lose ground and would be intermittent. After fixing that, the alternator is really cranking out power like it should. I took it out last night and it definitely ran better. I think now it is a matter of adjusting the carb to get the air fuel mixture correct. It smells rich at start up. Will play with it and see if I cannot get it running right. One question, though, after I ran it last night, I cut off the ignition and tried to restart it. It would not restart. It would turn over, but not start. Any thoughts there?

[Michael W.]

Re: 1967 won't run after 30 minutes

It would not restart. It would turn over, but not start. Any thoughts there?

The alternator was not the problem.

You need to see whether you're missing fuel or ignition when it won't start.

[Donald O.]

Re: 1967 won't run after 30 minutes

So I got the alternator back and I think the main problem is solved. Apparently when the repair guy opened up the case, the ground screw for the brushes was backed almost all the way out. He said that this would cause the alternator to lose ground and would be intermittent. After fixing that, the alternator is really cranking out power like it should. I took it out last night and it definitely ran better. I think now it is a matter of adjusting the carb to get the air fuel mixture correct. It smells rich at start up. Will play with it and see if I cannot get it running right. One question, though, after I ran it last night, I cut off the ignition and tried to restart it. It would not restart. It would turn over, but not start. Any thoughts there?

Does it start today?

[Lee B.]

Re: 1967 won't run after 30 minutes

I installed the alternator and made sure the timing was right. Everything was working as it should. However, it was still not restarting after getting up to operating temp. Last night, I drove it around and it started backfiring and then cut off. Would not restart. I replaced the coil and it immediately fired up. This was the new NAPA coil that is 2 weeks old. Could the alternator when it was not producing enough voltage made it hard on the coil so that the coil was failing? IF this is the case, then every time I replaced the coil, the car would run right until the coil would break down. Never thought I could have that many bad coils, but if the low voltage was destroying them. If that is not the cause, please let me know, because I need to keep looking for what the culprit is. Thanks as always,
Lee

[Michael W.]

Re: 1967 won't run after 30 minutes

That's not the cause, sorry.

Aside from a string of bad luck with poor quality coils, it would be over voltage (too much current ) or overheating that would cause them to fail

Sure you've got the right ballast resistor?

[George J.]

Re: 1967 won't run after 30 minutes

Did you change the condenser when you changed the coil. I had both fail at the same time. I was on a trip to the Corvette museum, coil went, changed that, but I still had inconsistent rough running, back firing, etc. Changed the condenser and all was well.

George

[Lee B.]

Re: 1967 won't run after 30 minutes

I thought the problem was solved again, but I took the POS out again tonite and it ran great for 30 minutes then started backfiring. I pulled over and changed out the coil with a new spare and it ran decent, Not great. Ran it a little longer adjusting the air fuel on the carb to see if I could get it to run better and then it cut off. Would not start. I put the original coil in and it started right up. The brand new coil that I had just put in 10 minutes before was hot as a firecracker. The now cooled off coil got me home. Pulled in the garage and cut it off. Would not restart. I am at my wits end. Any other ideas?
Thanks
Lee

[Michael W.]

Re: 1967 won't run after 30 minutes

I The brand new coil that I had just put in 10 minutes before was hot as a firecracker.

Points to the ballast resistor.

[Lee B.]

Re: 1967 won't run after 30 minutes

Points to the ballast resistor.

I checked the voltage input and output of the ballast and got 14.3 input and 10.5 on the output side of it. Is that correct?

[Joe C.]

Re: 1967 won't run after 30 minutes

See post #7.
The plugs should be gapped at .035. A wide gap will over work the coil.

[Lee B.]

Re: 1967 won't run after 30 minutes

Just replaced the plugs gapped at .035. For the record, the old plugs looked good.

[Stephen L.]

Re: 1967 won't run after 30 minutes

Have you checked the voltage at the coil itself when attempting to start the engine (full voltage) and while running (reduced voltage)? Your initial post said the car was completely restored and hasn't run correctly since. Did you install a new wiring harness? Have you checked the wiring closely for proper connections per the wiring diagram? Possible wiring error in the harness (if new)..... Just some thoughts......

[Duke W.]

Re: 1967 won't run after 30 minutes

I just reviewed the whole thread and everything seems to have been checked and double checked including swapping in different coils and ballasts.

The fact that the problem does not occur with a jumper installed between the battery pos. terminal and the coil + terminal indicates high resistance or an intermittent open somewhere in the circuit. All that's left is the ignition switch and harness.

One test is to jiggle the key while the car is running properly, and if it starts to stumble, it's definitely suspect. It would also be a good idea to read voltage at the coil plus terminal while running this test, and you can run it idling in the driveway. I'm not sure if the ignition switch can be disassembled, but it has mechanical contacts, so removing it for continuity testing and cleaning with electrical contact cleaner is a path, or buy one and see if that solves the problem.

That leaves the new harness. I believe it has one or more internal splices, and of course there are many terminal crimps, all of which could be suspect. If the ignition switch can be eliminated as a cause contact the harness vendor, review the problem and ask them to send you a new harness for an on-the-car test.

Duke

[Joe C.]

Re: 1967 won't run after 30 minutes

I just reviewed the whole thread and everything seems to have been checked and double checked including swapping in different coils and ballasts.

The fact that the problem does not occur with a jumper installed between the battery pos. terminal and the coil + terminal indicates high resistance or an intermittent open somewhere in the circuit. All that's left is the ignition switch and harness.

One test is to jiggle the key while the car is running properly, and if it starts to stumble, it's definitely suspect. It would also be a good idea to read voltage at the coil plus terminal while running this test, and you can run it idling in the driveway. I'm not sure if the ignition switch can be disassembled, but it has mechanical contacts, so removing it for continuity testing and cleaning with electrical contact cleaner is a path, or buy one and see if that solves the problem.

That leaves the new harness. I believe it has one or more internal splices, and of course there are many terminal crimps, all of which could be suspect. If the ignition switch can be eliminated as a cause contact the harness vendor, review the problem and ask them to send you a new harness for an on-the-car test.

Duke

That's all great advice, but I already gave it in posts #24 and #42.
If the switch and/or associated wiring have high resistance, then they will get hot.