1967 won't run after 30 minutes

[Lee B.]

Re: 1967 won't run after 30 minutes

What voltage should I see at the positive side of the coil?

[Stephen L.]

Re: 1967 won't run after 30 minutes

You indicated earlier that you see 14.3 volts and 10.5 volts at either end of the ballast.
While in a "start" condition (starter engaged, engine not running) you should see about 12 volts (some voltage loss due to the load from the starter on the battery during start) and with the engine running, about 9-10volts.
If the voltage remains the same under both conditions (start and run) then your ballast resistor is never switched into the coil circuitry causing excessive continuous 12+v coil voltage, high current, and higher coil temps over time... in your case about 30 minutes of run time, resulting in a breakdown of the coil. Once the coil cools it will again function normally, but eventually will destroy itself.
The start voltage (12v comes from a contact on the starter solenoid marked "R" (pink #18 wire) and the reduced voltage comes from the ballast resistor (9-10v) which is supplied on the opposite end, by the ignition switch (12+ volts)
There is a possibility of the solenoid being wired incorrectly or being faulty, with the "R" contact, internal to the solenoid, ALWAYS connected to the 12v battery source, which then, electrically, bypasses the ballast.

[Lee B.]

Re: 1967 won't run after 30 minutes

Just got home from work and tested the voltage. Turned the key to start and the meter reads 5.3 volts at the output of the ballast resistor and at the positive side of the coil. The battery reads 12.3 volts. Cranked the motor and the battery reads 14, output of the BR reads 9.5 and the positive side of the coil reads 9.5. I am guessing that there is a wiring issue at the starter? Correct? Stephen and several others say that I should read the same as the battery when the key is in the on position but the car has not been started. I will pull the starter this weekend and see if it is wired correctly. After the issue with the ground in the alternator, I am now questioning the starter since it was rebuilt by the same guy.
Am I missing anything?
Thanks
Lee

[Donald O.]

Re: 1967 won't run after 30 minutes

Lee,
No need to pull the starter. No need to re-rebuild the starter. Just check the connections at the starter making sure they match the wiring diagram.
Your problem lies in the wiring to the coil and the ballast resistor. You should have battery voltage at the positive side of the coil with ignition ON and reduced voltage after the engine has started.

Don

[Michael W.]

Re: 1967 won't run after 30 minutes

Just got home from work and tested the voltage. Turned the key to start and the meter reads 5.3 volts at the output of the ballast resistor and at the positive side of the coil.

This reading is meaningless as you don't know if the points are opened or closed. The other reading are helpful.

[Stephen L.]

Re: 1967 won't run after 30 minutes

Lee, the starter itself is NOT the problem. As said no need to rebuild the starter. What I said earlier is that there is possibly a problem with the wiring correctly connected at the starter solenoid OR a problem internal to the starter SOLENOID. Inside the solenoid is a large copper disc that contacts the main battery power lug to the starter motor lug when the solenoid is energized by the key switch. Obviously this portion is working as the starter will rotate and the engine starts.
Also inside the solenoid is a smaller contact (R) that makes contact with the disc during "START". This now supplies battery voltage direct to the coil via the (R) contact and pink wire.
When the ignition key is released from the start position the disc retracts away from both contacts mentioned above and the battery voltage is removed from the (R) contact, and the starter motor quits turning.
Do you measure ANY voltage at the positive terminal on the coil with the engine and key off??? If voltage is present, this would indicate a wiring problem.

Another test would be to disconnect the (R) pink wire at the starter solenoid and tape it up. Start the engine. (It may be hard to start due to low voltage at the coil as only the ballast will be in the circuit).
Drive the car for 30 minute test. If it still has the performance problems, then you probably have a wire problem in the harness as you have isolated the starter solenoid battery voltage supply from the coil.

[Gene M.]

Re: 1967 won't run after 30 minutes

Hard starting issue is most likely flooding with fuel or ignition/spark. I'll assume timing is still good. I suggest you check the points and dwell as was suggested already by others. Along with that change the points condenser to eliminate the remote possibility of it failing. I had a brand new failed points condenser that drove me nuts years ago.

Since coils were swapped out make sure the negative coil terminal is wired to the distributor. Engine will run with it wired backwards but very poorly and get hot. I suggested this because it was mentioned the coil was hot.

[Joe C.]

Re: 1967 won't run after 30 minutes

Anecdotal evidence to the contrary: I have a 327 small block in my jet boat that I've owned for 40 years. It does not have a ballast resistor, nor a coil intended for use with a ballast resistor. Same coil now for 20 years, no problems with the coil overheating or engine stalls or anything else. The original coil lasted the first 20 years until the key got left on overnight and destroyed it.

I'm not advocating the removal of, or running without a ballast resistor, just that in my case it has not resulted in any problems in 40 years of running without one. (I won't bore you with why I don't run one on the ski boat).

I agree the OP's issue appears to be with primary supply voltage.

That's not the case here. Coils intended for use without an external ballast are designed with different primary resistance than coils designed for use with external ballast.

[Stephen L.]

Re: 1967 won't run after 30 minutes

Dave, 1967 GM's still used a ballast resistor.
In 1968 or 1969 GM went to an "inline" resistance wire (cost reduction???) typically in the harness exiting the bulkhead connector. The value of resistance is called out as 1.35 ohms for V8 engines. There may be a chance that the wiring for your boat has this feature and you are not aware of it as it is sometimes "buried" in the harness. Per my 1972 CHEVELLE GM SERVICE MANUAL: the coil is specifically designed to be used with an external resistance. Expected voltage at the coil + is approximately 8VDC. This lower voltage provides for longer life.
I don't know if this info necessarily pertains to later GM HEI systems........

[Lee B.]

Re: 1967 won't run after 30 minutes

I finally fixed the problem. The solenoid on the starter was wired incorrectly. I expect the start and run wires were wired backwards. I replaced the solenoid and the car runs great. Pirkle had my starter, alternator, a/c switch when he died. I expect my stuff was unfinished and just thrown back together. The alternator and solenoid both had problems. Not throwing stones, just stating what happened. Anyways, everything seems to be running great. Thanks for all the help.

[Ralph E.]

Re: 1967 won't run after 30 minutes

HOORAY for Lee!
Glad you finally got it figured out.
What made you go back to the starter/solenoid after all this time?
In hind sight it almost seems you should have started at the starter since that had been worked on. Think someone even suggested it.
Again, glad you got it fixed. Now drive it like you stole it!

[Lee B.]

Re: 1967 won't run after 30 minutes

I had tried everything else and was trying to wait until I got my new garage and lifts in. Got the opportunity to use someone else's lift and put the new solenoid in. Still running great. Now I can get back to making the car look nice since it actually runs. What a fiasco and waste of time and lots of money.

[Walter R.]

Re: 1967 won't run after 30 minutes

Did anyone get an answer to Lee's problem? I am having a similar issue with a 1966 L72 with TI.

[Jack H.]

Re: 1967 won't run after 30 minutes

Did anyone get an answer to Lee's problem? I am having a similar issue with a 1966 L72 with TI.

Reply #101 above says that a new solenoid fixed the problem.